Can a bad car battery cause an alternator to not charge?

Table of Contents

Can a bad car battery cause an alternator to not charge?

In theory a car can run only with the alternator charge, but this can cause heavy voltage spikes and other strange symptoms so this means that a bad car battery can cause an alternator to not charge also. Cars are increasingly coming with modern electronics.

Can a bad solenoid cause a car to not start?

If your car’s solenoid or starter are bad, the lights will shine brightly but the engine will not start. Once the alternator stops working, so do all of the electrical systems required to keep a car going. Other problems can also cause a car to not start.

What causes an alternator to go over base voltage?

If you are getting more than 2 volts above base voltage, most likely your alternator is over-charging the battery or the battery is faulty. Other potential problems are a faulty voltage regulator or a problem in the charging system wiring.

Is the alternator the only thing that powers the car?

Many people assume that the car’s battery is the only thing that powers all electrical components in the car. But, this is not true. The alternator plays a vital role in supplying power to the car’s AC, recharging the battery and ignition.

Can a bad battery cause an alternator to over charge?

Make sure that all the connections to the alternator, remote voltage regulator (if applicable) and battery are clean, tight and in good condition. Check your battery or have it tested at your local auto parts store. A bad battery cell can cause the alternator to over-charge the good battery cells.

What kind of battery does a GMC coach have?

The GMC has two banks – the engine (usually one battery) and the coach bank (a 12V or 2, 6V). Some coaches have added a third bank to extend the time between recharges. Statpower- a company that manufactures a variety of battery related equipment including chargers and inverters. >statpower40, TrueCharge 40, TrueCharge 40+

Why is the voltage reading on my alternator going up?

While watching the voltmeter display, start wiggling wires at the back of the alternator, the battery, and the remote voltage regulator (if there is one). If the voltage reading on the meter display goes up while wiggling one of the wires, you’ve found a bad electrical wire or connection.

How is the shorepower charger connected to the alternator?

The alternator is connected to the engine battery and the shorepower charger is connected to the house battery. When the alternator has charged the engine battery up to 13.2 volts, the COMBINER connects the two battery banks together to charge the house battery.

What happens when the alternator of a car is dead?

The alternator and the car’s battery work hand in hand. A good battery should give you service for the next five years before its lifespan ends. If your battery is dead, then it will not give power to the car’s alternator. The alternator normally lasts longer than the battery.

How can I tell if I have an alternator problem?

To differentiate an alternator problem from the battery, you will need to use a voltmeter to check for voltage. First, turn off the engine and check the battery voltage. A fully charged battery should have a reading of 12.65 volts. Next, turn on the engine and recheck the voltage. You should have a reading of 13.5 to 14.5 volts.

What happens to a car battery when the alternator goes bad?

As batteries age, they become less able to retain a charge because the metal inside corrodes. Eventually, the level of battery charge diminishes to the point where, no matter how much power the alternator gives to it, the battery can’t hold enough power to start the car.

What should I do if my alternator goes short?

Disconnect the big main cable to the alternator and see if the short goes away. If it does, then use your meter to measure the ohms between the alternator post and the alternator case. You should have continuity in one direction and if you switch leads you’ll have no continuity. This will tell you the diodes are good or shorted in the alternator.

To differentiate an alternator problem from the battery, you will need to use a voltmeter to check for voltage. First, turn off the engine and check the battery voltage. A fully charged battery should have a reading of 12.65 volts. Next, turn on the engine and recheck the voltage. You should have a reading of 13.5 to 14.5 volts.

How long does an alternator last in a car?

On average, car batteries last between 2 and 5 years. Eventually, the level of battery charge diminishes to the point where, no matter how much power the alternator gives to it, the battery can’t hold enough power to start the car.

What’s the charging voltage on a Honda Accord?

is engaged), the ECM will set the charging voltage to 14.4-14.9V (high output mode); during startup and light electrical load conditions, the ECM will set the charging voltage to 12.4-12.9V (low output mode). In the latter case this anomaly might cause a technician to try to diagnose a low charge problem, although it is

What makes Honda’s electric car charging system unique?

The single component that makes Honda’s charging system unique is the electric load detector located inside the fuse box. In some cases the fuse box will have to be dismantled to gain access to the ELD. This sensor informs the ECM of the amount of electrical energy being used by the vehicle. The ECM sends a 5V

What does it mean when Honda alternator is not charging?

CASE 2: Your multimeter registered a voltage that steadily dropped down to 9 Volts. This is a clear indication that your Honda’s alternator IS NOT charging the battery. Replacing the alternator at this point usually solves around 90% of the No Charge Conditions on any Honda Accord (or Odyssey or Prelude or any 2.2L, 2.3L Honda) around the world.

What to do if your Honda Accord battery won’t charge?

Use a voltmeter to check the battery’s output. If the reading shows 14.5 volts or less when the car is running, it should be changed. Figure 1. An overused battery. If the battery is worn out, first have it replaced with a new one. This will pinpoint other mechanical problems because those depend on a battery that is in good condition.

Can a faulty alternator be traced to fuse 15?

Tracing the alternator’s problem to fuse 15 can prevent the need for a new alternator or battery and save you a lot of money. The alternator recharges your battery when the car is in motion. If it’s faulty, the battery of your vehicle will not hold a charge. To diagnose a faulty alternator, you will need to do the headlight test.

Where is the ELD on a Honda alternator?

When the alternator reports a problem to the ECM, the ECM sets a trouble code and communicates digitally with the gauge control module to light the BATTERY light on the instrument cluster. The ELD inside the fuse box or at the battery terminals.

When to replace battery, alternator, or starter?

When you check these three, always start with the battery. It’s most often the part that failed, and it’s also the cheapest part to replace. A car battery should last about four to five years. It is not made to hold a charge for that long, so it gets recharged by the car’s alternator while you drive.

Can a car not start but the battery is good?

If you see the lights working and the radio functioning and thought that battery is good, this is not the right conclusion.

What does it mean if your alternator is not working?

The Alternator A dead car battery is the first sign that something might be wrong with the alternator. If your battery is good, and your alternator isn’t working, the battery will still lose its charge because the alternator isn’t keeping it charged.

Why does my car not start with a new battery and alternator?

With a new starter, battery, and alternator (assuming you have not drained the battery attempting to start it), the starter should attempt to crank over the engine. If the starter does not make any noise when the key it turned to crank over the engine, you have an issue with the fuses, or the circuit.

Can a bad car battery be a bad battery?

It very well can be a bad battery even though the lights come on. Starting the car is the single hardest thing (draws a lot of amperage) for the battery to do. If it is becoming weak, it will become harder and harder for it to crank the engine.

What to do if your car battery wont start?

If it is becoming weak, it will become harder and harder for it to crank the engine. The lights and other accessories may still work because they draw less amperage (which the battery can still support). Take the battery to have it load tested. That will determine if it is still good or not.

Is the battery good for a new car?

Battery is fine all lights come on in car. Car will even almost start just missing that last step. I am only able to overcome the last step when I use jumper cables. Battery is not good, just because it light lights, does not mean it will start the engine. Replace the battery. – Moab Aug 6 ’16 at 17:22

How long can a battery last without an alternator?

A good alternator and can last well over a decade, sometimes as long as 15 to 20 years. However, if an alternator does fail on you then you’ll know it fairly quickly as your electrical systems will fail soon afterwards. The charge in your battery does not last long without the alternator there to keep it running properly.

What should I do if my alternator is not working?

The solution is to check your car’s manual for the particular fuse that controls the alternator and replace it. In some cars, you might also find another small fuse to the alternator’s control—usually a 15A to 20A fuse. An alternator does usually has 3 or 4 wires to it to function properly.

Why is my Honda alternator not charging the battery?

I was in the process of limping it home when I realized that the alternator was not charging the battery (pulled the negative cable off the battery and the van died). No bid deal, Im a mechanic so I went to Advance Auto Parts and got a replacement alternator. Put it on, charge the battery and problem solved for a while.

What happens when an alternator goes bad in a car?

The alternator plays a vital role in supplying power to the car’s AC, recharging the battery and ignition. When your alternator is faulty, the battery power is drained fast, and you will find yourself with a stalled car. But what can cause the alternator to go bad?

What should battery voltage be when alternator is not charging?

The alternator is connected to a set of belts which when loose can cause it not to function as required. To differentiate an alternator problem from the battery, you will need to use a voltmeter to check for voltage. First, turn off the engine and check the battery voltage. A fully charged battery should have a reading of 12.65 volts.

A good alternator and can last well over a decade, sometimes as long as 15 to 20 years. However, if an alternator does fail on you then you’ll know it fairly quickly as your electrical systems will fail soon afterwards. The charge in your battery does not last long without the alternator there to keep it running properly.

Why is there a noise coming from my alternator?

Noise from the alternator could be caused by a faulty rotor shaft, rectifiers, bearings, slip rings, stator winding or brushes. You will need to carefully inspect each of these components and replace them. One sure way of confirming that the noise is coming specifically from the alternator is to use a vacuum hose.

What does it mean when your alternator stops the car?

If you can’t get it to restart, this is a sign the alternator is doing its job of keeping the battery working while the motor is running, but the battery isn’t retaining the charge when the alternator has stopped. The car battery could be old. As batteries age, they become less able to retain a charge because the metal inside corrodes.

When to know if your alternator or battery is dead?

If the engine starts but dies immediately, your alternator probably isn’t keeping your battery charged. If a jump starts and keeps your car running, but the car can’t start again off of its own power, a dead battery is likely your answer.

How does an alternator start and run an engine?

Starting and running an engine, in its simplest form, is a three-step process. First, the battery delivers a jolt of electricity to the starter. This starts the engine running, which puts the alternator into action. Finally, the alternator completes this cycle by charging the battery.

How do I know if my battery or alternator is bad?

Signs of a bad alternator. If the above steps reveal that the battery is working, it’s time to take a closer look at the alternator. There are certain signs of a bad alternator to look for: While running the car, note the brightness of the interior lights. If the dashboard gradually dims, the alternator is likely at fault.

Can a bad alternator damage a battery?

For one, a bad alternator can kill a battery, even if it was not the battery that was the issue to start with. When the alternator is going bad, the battery picks up the slack of providing electricity to the car’s electrical system.

How do I know if it is the battery or the alternator?

Check the Alternator. Test the alternator to make sure that it can start up the battery. If the battery is working properly and nothing is wrong with it, then it’s the alternator that will more likely cause a problem. Try to start the engine and listen carefully, if it produces a “whining” sound, it may be the alternator.

What makes alternator go bad?

Causes of a Bad Alternator. One of the most common problems of a faulty alternator is a loosened belt. The diodes of the alternator can go bad, failing to transmit the required voltage. The bearings on which the alternator rotates can also be at fault and hinder the alternator from providing an optimal performance.

What should I do if my alternator keeps dying?

The alternator is essentially a generator and it keeps your battery charged while supplying additional electrical power for the other systems in the vehicle. If you have a new alternator and your battery keeps dying on you, then there’s definitely a problem that you’re going to need to look into.

What kind of energy does an alternator use?

It converts alternating current (AC) to direct current (DC). It must supply enough electrical energy to the battery for recharging, along with maintaining sufficient voltage to run the vehicle’s accessories and components.

What happens if you have a new alternator and the battery is not charging?

The alternator in your car is an integral part of your vehicle’s electrical system. If you have a new alternator and the battery is still not charging, then you definitely have some kind of a problem with your battery that you’ll need to address immediately.

The alternator is essentially a generator and it keeps your battery charged while supplying additional electrical power for the other systems in the vehicle. If you have a new alternator and your battery keeps dying on you, then there’s definitely a problem that you’re going to need to look into.

Why does my car not start when I jump the alternator?

If jump starting gets your engine started and running, but the car will not start again once you turn it off, the battery is probably the problem. In this case, the alternator is doing its job of keeping the battery going once it has been jumped, but the battery can’t hold a charge when the alternator is shuts off.

If that’s all good then replace the regulator. If not then buy a rebuilt alternator and install it (the rebuilt will come with a regulator). If you’re not very well DIY inclined you could just buy the rebuilt alternator and do the R&R, that’s pretty simple (just be sure to disconnect the battery first!).

What is the fault code on a Lexus?

LEXUS Car Manuals PDF & Wiring Diagrams above the page – CT, ES, GS, LS, LX, NX, RC, RX, IS, UX; Lexus Cars EWD s; LEXUS Fault Codes DTC. Lexus is a division of Toyota, a Japanese company that was created to develop and manufacture luxury cars.

Why does my alternator make noise after replacing the belt?

If the noise continues after replacing the belt, then you need to replace the alternator. In addition, noise from the alternator could be due to a damaged rotor shaft, rectifiers, slip rings, or brushes. You need to be sure to inspect each of these parts in order to determine which one is making the noise.

In theory a car can run only with the alternator charge, but this can cause heavy voltage spikes and other strange symptoms so this means that a bad car battery can cause an alternator to not charge also. Cars are increasingly coming with modern electronics.

If you are getting more than 2 volts above base voltage, most likely your alternator is over-charging the battery or the battery is faulty. Other potential problems are a faulty voltage regulator or a problem in the charging system wiring.

The alternator and the car’s battery work hand in hand. A good battery should give you service for the next five years before its lifespan ends. If your battery is dead, then it will not give power to the car’s alternator. The alternator normally lasts longer than the battery.

How long does a car battery last without an alternator?

If you are lucky and could get up to two hours. Note: In case you have to start the car without an alternator, don’t turn off the engine once you’re going. Starting the car flattens the battery down quickly. Starting a car uses ten times more juice than everything else put together.

Why does my car battery not charge when I start the engine?

But once the engine has started, the alternator should recharge the battery. When the engine starts turning, the alternator is driven by a belt that converts mechanic power to electrical power.

Why would a good alternator not charge a battery?

The alternator is powered by several different wiring mechanisms. If a wire is not attached properly, becomes detached or is inadvertently cut, the alternator will not have any power. If the alternator is not getting any power, it cannot turn the pulley and belt mechanism that charges the battery, and the battery will not charge.

What causes your alternator not to charge?

There are several different problems that can cause your alternator to stop working. Your car’s alternator charges the battery by generating power with a pulley and belt system. If the belt that controls that system snaps, stretches out or breaks, the alternator will stop working, and the battery will not charge.

Can a bad alternator damage battery?

A bad alternator can cause a dead battery and other problems with vehicle systems like the stereo and power windows. But there’s good news here, because even an automotive novice can watch a video or two and figure out how to change their own alternator.

Would an alternator run down a battery?

An automotive alternator is a device that converts power from the engine into electricity, which is used to charge the car’s battery. In some cases, however, the alternator can actually drain the battery, causing significant problems. An alternator that’s not providing enough power can allow a battery to run down.

How can I tell if my alternator is charging?

The alternator is charging if the battery voltage stays above 13 volts with the engine at 2,000 rpm and all accessories on. Check the alternator gauge. If you have a volt/amp gauge, it will read the alternator output for you.

Why isn’t my alternator charging my battery?

6 Causes of an Alternator Not Charging Worn out carbon brushes or damaged alternator. The most common reason why your car is not charging is actually because of a worn-out or damaged alternator. Broken Serpentine belt. Faulty fuse. Wiring issues or connectors. Damaged car battery. Engine control module error.

Can a bad alternator overcharge a battery?

Overcharging of the battery by a defective or malfunctioning alternator will result in the battery reaching an overcharged state. When overcharged, the plates inside the battery shed material and lose their capacity to hold electricity. The battery resists further charging, and the excess electrical charge builds up and is radiated as heat.

What to do if your alternator is draining your battery?

In summary, a faulty alternator can drain your vehicles ‘battery. To test whether an alternator is draining the battery, with the car’s engine switched off disconnect the car’s electrical system leaving the battery only.

How can I tell if my alternator is working or not?

If you’re not 100% sure, you can use a multimeter, or a voltmeter, to check the current coming from your battery. Attach the positive lead to the positive battery terminal, that’s the red one, and then the negative leave it to the black terminal. With the engine off you should be getting a reading of 12.5 volts on your multimeter.

The solution is to check your car’s manual for the particular fuse that controls the alternator and replace it. In some cars, you might also find another small fuse to the alternator’s control—usually a 15A to 20A fuse. An alternator does usually has 3 or 4 wires to it to function properly.

What can cause a car battery to overheat?

It may have damaged your battery. Since the alternator regulates how much electric current gets fed back to the battery during recharging, the battery may have overheated due to overcharging. This shortens its expected life and can make it unreliable. Ask whether you need a replacement if you’re having alternator repairs done.

What to do when your alternator stops working on your car?

After running the motor for a while, turn the car off. If you can’t get it to restart, this is a sign the alternator is doing its job of keeping the battery working while the motor is running, but the battery isn’t retaining the charge when the alternator has stopped. The car battery could be old.

Is the alternator at the heart of the charging system?

Dan Ferrell writes about do-it-yourself car maintenance and repair. He has certifications in automation and control technology. The alternator is at the heart of the charging system of your vehicle. Alternator problems and charging system problems can affect your vehicle in different ways.

What should I do if my alternator is not charging?

The alternator normally lasts longer than the battery. There are some easy steps you can go through to check the function of your alternator. Tap the alternator carefully with a hammer while the engine is runnin; if the charging goes back to normal, the coals inside it are worn out.

If you can’t get it to restart, this is a sign the alternator is doing its job of keeping the battery working while the motor is running, but the battery isn’t retaining the charge when the alternator has stopped. The car battery could be old. As batteries age, they become less able to retain a charge because the metal inside corrodes.

Can a broken belt cause an alternator to not charge?

The alternator will not be able to charge if your belt wears down over time. Fortunately, the broken belt is easy to replace, and can be a quick fix to get your alternator backup and charging again. A broken pulley goes hand-in-hand with the broken belt. The pulleys and belts are part of the system which converts energy into the alternator.

Why does my alternator get higher than base voltage?

You should get 0.5 to 2 volts higher than base voltage. If you are getting more than 2 volts above base voltage, most likely your alternator is over-charging the battery or the battery is faulty. Other potential problems are a faulty voltage regulator or a problem in the charging system wiring.

What happens when the serpentine belt fails on an alternator?

The serpentine belt powers the alternator, and if it fails, the alternator will stop working the moment your belt wears out and breaks, or the pulley becomes damaged. This can also happen if the serpentine belt is not tightened correctly. Most cars have automatic tensioners, but these can fail, so it is better to double-check.

Noise from the alternator could be caused by a faulty rotor shaft, rectifiers, bearings, slip rings, stator winding or brushes. You will need to carefully inspect each of these components and replace them. One sure way of confirming that the noise is coming specifically from the alternator is to use a vacuum hose.

The serpentine belt powers the alternator, and if it fails, the alternator will stop working the moment your belt wears out and breaks, or the pulley becomes damaged. This can also happen if the serpentine belt is not tightened correctly. Most cars have automatic tensioners, but these can fail, so it is better to double-check.

Where does the charging warning light go on an alternator?

Black and yellow goes from the alternator plug to that generator relay. Blue wire goes from generator relay to that interior harness (C25) which goes to the instrument panel wiring (My 3rd pic the plug on the left) which looks to be for the instrument cluster for the “charging warning light”. Click to expand… Gotcha.

What does it mean when your alternator is not charging?

If the alternator is not charging the battery, you will have a red “ALT” or “charge” sign on your dashboard. This means that your battery is no longer being supplemented for power by the alternator. You will need to recheck the wiring because the light could also be faulty.

Can you drive a car with a faulty alternator?

Faulty diodes can easily be replaced, but you will need to dismantle the alternator. It is impossible to drive the car with a faulty alternator. While it is the work of the battery to power the electrical components in the car, it cannot do this alone.

How can I tell if my alternator or battery is OK?

As with most electrical issues, if you know the battery or alternator is OK (because you had it tested), then diagnosis comes down to tracing and testing for continuity from one portion of the circuit (s) involved to the next.

Why does my Infiniti G35 not start up?

While there are a variety of reasons your Infiniti G35 won’t start, the most common 3 are a dead battery, an alternator problem, or failed starter.

Many people assume that the car’s battery is the only thing that powers all electrical components in the car. But, this is not true. The alternator plays a vital role in supplying power to the car’s AC, recharging the battery and ignition.

How can you tell if your car charger is in trouble?

Usually, the first sign that your charging system is in trouble is a “battery,” “ALT,” or “CHARGE” warning light illuminating on your instrument panel while driving. It means that for some reason, the alternator has stopped charging the battery and your car is running on battery power.

Can you tell if a car battery is bad?

I have repaired a lot of different stuff, from computers, to appliances, to cars and even airplanes, if it is around the house, I have likely fixed it. I hope you enjoy the videos and you find something useful. Please share so others can learn how to fix things themselves. How to tell if your car battery is bad, weak or dead.

What do I need to know about my car charging system?

These series of charging system checks help diagnose the general condition of your charging system. They can help you confirm that you actually have a problem in your charging system and locate the source of the problem. 1. Make a Visual Inspection of the System

Is there a problem with the Nissan 240SX battery?

Charging Problem – Battery Not Charging but Alternator OK! – Nissan Forum | Nissan Forums Charging Problem – Battery Not Charging but Alternator OK! ONLY for ADVANCED technical discussion about the 240sx! Charging Problem – Battery Not Charging but Alternator OK!

What to do if your car battery is not charging?

(The guy on the desk checked the battery and advised that the volts were good but the CCA were a bit on the low side.) Re-fitted the battery to the car and turned the key – noticed that none of the dash lights illuminated? The Clock section was lit up but no sign of the LCD display.

Why is my battery not charging but alternator is OK?

I have no power to almost everything in the car… The air blowers change position and the a/c kicks in as I heard a change in engine note and the selector switched illuminates but the fan does not work. All of the fuses appear to be OK…

Usually, the first sign that your charging system is in trouble is a “battery,” “ALT,” or “CHARGE” warning light illuminating on your instrument panel while driving. It means that for some reason, the alternator has stopped charging the battery and your car is running on battery power.

What does it mean when your alternator stops charging the battery?

Indicator Light On. Usually, the first sign that your charging system is in trouble is a “battery,” “ALT,” or “CHARGE” warning light illuminating on your instrument panel while driving. It means that for some reason, the alternator has stopped charging the battery and your car is running on battery power.

If your not getting a reading from there you can check your output from your alternator. Make sure you ground your multimeter, and put the power side to the stud that is coming out from the alternator (should be nut holding your wires that go to your battery).

What happens when the diodes in an alternator go bad?

Alternators use diodes to rectify alternating current produced by the alternator into direct current. When one or more diodes go bad, the alternator can cause all kinds of problems. AC voltage leak can cause your lights to dim and drain power from your battery, for example.

What should the alternator voltage be at rest?

Here’s why: The battery’s voltage, at rest, is 12.5 Volts. So one of the best indicators that the alternator is charging it, is verifying that battery voltage should be at 2 Volts over battery voltage (at rest) when the engine is running.

How to test the alternator in a mini van?

So these are the steps: Start the car or mini-van and test the battery voltage with your multimeter by placing the RED multimeter’s test lead on the positive battery terminal and the BLACK test lead on the negative battery terminal. Your multimeter should read 13.5 to 14.5 Volts. If it doesn’t, don’t worry about this just yet.

A really bad car battery might actually not take care of the charge from the alternator, which will cause the alternator not to charge at all. In theory a car can run only with the alternator charge, but this can cause heavy voltage spikes and other strange symptoms so this means that a bad car battery can cause an alternator to not charge also.

How many wires does an alternator need to charge?

An alternator does usually has 3 or 4 wires to it to function properly. You will find one big main cable together with two or three small ones. All these wires are important for the alternator’s function, and if one breaks off – you might lose the charging function.

Where does the alternator go in a Mitsu?

The alternator harness goes to the fusebox and that diode or the “generator relay” that Mitsu calls it hangs around the fusebox. Then, you have those 4-white wires that go into the fusebox between the 100A fuse and the fusible link. I am doing a wire tuck right now.

How long does it take for an alternator to fully charge?

Only if it is about ready to fail anyway. It does put a very high load on the alternator and will make it quite hot. It can take several days for the battery to fully charge under normal driving. The extra load can take out an old belt due to slippage.

Can a bad alternator Fry a new battery?

The flip side is that a defective alternator can fry a battery, also. So replacing a battery and having the new one go bad soon afterward might mean the alternator was bad to begin with. A depressingly large number of people don’t test the charging system after replacing a battery.

How can you tell if your car has a bad alternator?

To find out more, review our article on signs of a bad alternator. When the engine is running, the alternator charges the battery, while also powering your car’s electrical system. The best way to find out whether your car needs a new alternator or a new battery is to test both components.

What happens when the belt on an alternator breaks?

A closer observation of the alternator will reveal a pulley and belt system that works to convert mechanical energy into electrical energy. The serpentine belt powers the alternator, and if it fails, the alternator will stop working the moment your belt wears out and breaks, or the pulley becomes damaged.

Why is the alternator on my Jetta not charging?

Cables ok, fuse 11 ok, tried a new battery, other battery showing 12.5 volts, system now charging 16.8 volts, dropped after about 10 minutes, noting that if engine raised above idle tact and insturment cluster shut off, I guess high voltage protection? After 20 min road test battery died, any sugestion on changing pcm?

https://www.youtube.com/watch?v=ELbGcSuMvZY

Dan Ferrell writes about do-it-yourself car maintenance and repair. He has certifications in automation and control technology. The alternator is at the heart of the charging system of your vehicle. Alternator problems and charging system problems can affect your vehicle in different ways.

What to do if your alternator has bad ground?

Place the red lead on the positive battery terminal (if possible dig it into the battery post, not the terminal). Place the black lead on the bad post of the alternator. Same thing as above, if the voltage is above 0.5v then examine the positive cabling for problems.

What should the voltage be on a bat alternator?

Measure the voltage across the battery and the big bat alternator terminal to alternator case. There are two things that you are looking for. The charging voltage should be between 13.9v to 14.4v. Also the voltage at the battery and the voltage at the alternator should be within 0.5v of each other.

What causes an alternator to output low volts?

If the voltage at the battery and alternator don’t match. For example the battery reads 12v and alternator reads 14v. This means that there is an issue with wiring. While applying the same conditions as above.