Car losing power and dying and I can't figure out why

[bonoz]

My car had been sitting in my parents garage for the last couple of years because I was in grad school. But now I want to revive it. I did an oil change and changed all the belts. I got the battery tested and they say that it's still good at the parts store. However, when driving the other day, all the lights started to flicker, the AC started losing power, the throttle response was gone, and eventually the car just stopped.

I tested the voltages at battery terminals and I was getting 12.05V with the car off. With it idling, I was getting around the same. I also checked the voltages at the level of the alternator with the car turned off and then idling. The number that I was getting when idling was around 12V as well.

I thought that maybe the alternator was the issue. So I replaced it. But the problem is still there: after sufficiently charging the battery with an external charger, the car runs and eventually dies once the battery runs out of charge.

I rechecked the voltages and honestly it's not any different with the new alternator.

I'm not sure what else could be the issue. Is it a fuse issue? But then why would the new alternator be producing 14V instead of 12V (these are numbers at the alternator terminals)?

Could it be that the engine is just not cranking out enough power to keep the alternator running?

Just not sure what's going on. Would appreciate some help. Thanks.

[pbonsalb]

Either battery or alternator are no good. Should be 12.6V off and 13.6 to 14.5 with working alternator engine running. Worth checking the battery and engine and alternator ground connections before buying the battery or alternator.

[shogun]

Is the battery light in the cluster on when you switch ignition on and then disappears? Or does it never come on when you switch ignition on? If it is always on a bit dim, then the alternator is the problem, I once had that on my M3, 2 alternator rectifier diodes were bad. Changed the cpl. rectifier and all was good.
If the light never comes on, then the alternator does not start charging. Change the bulb in the cluster. Check correct wiring.The importance of having an operational warning light for the alternator (idiot light) is crucial. In most modern systems, the electrical current passing through the filament of the warning light is what energizes a circuit in the alternator to start charging.
see page 1230.0-00 charging system, from instrument cluster goes the line to D+ X6509 http://wedophones.com/Manuals/BMW/19...g%20Manual.pdf
E36-Exciter-Wire-Problem https://www.bimmerforums.com/forum/s...r-Wire-Problem
https://www.bimmerforums.com/forum/s...ng-Need-advice!

[bonoz]

Could a bad battery be affecting alternator output?

[bluptgm3]

If it sat for two years, I suspect the battery is the issue.
Check the fluid level, add distilled water as required.
Then trickle charge the battery for at least two days. Check voltages as described above once again.

[bonoz]

If it sat for two years, I suspect the battery is the issue.
Check the fluid level, add distilled water as required.
Then trickle charge the battery for at least two days. Check voltages as described above once again.

Would a bad battery be affecting the alternator output?

[bonoz]

Is the battery light in the cluster on when you switch ignition on and then disappears? Or does it never come on when you switch ignition on? If it is always on a bit dim, then the alternator is the problem, I once had that on my M3, 2 alternator rectifier diodes were bad. Changed the cpl. rectifier and all was good.
If the light never comes on, then the alternator does not start charging. Change the bulb in the cluster. Check correct wiring.The importance of having an operational warning light for the alternator (idiot light) is crucial. In most modern systems, the electrical current passing through the filament of the warning light is what energizes a circuit in the alternator to start charging.
see page 1230.0-00 charging system, from instrument cluster goes the line to D+ X6509 http://wedophones.com/Manuals/BMW/19...g%20Manual.pdf
E36-Exciter-Wire-Problem https://www.bimmerforums.com/forum/s...r-Wire-Problem
https://www.bimmerforums.com/forum/s...ng-Need-advice!

I will run these tests and get back to you. Do you think it could just be a bad battery that is keeping the alternator from performing?

[XnWarden]

I have never heard of a bad battery causing a car to die while it is running. You checked the electrical system for short circuits?

After all the stress on it, the battery will likely need replaced too. But something else is definitely going on here.



Sent from my SM-G975U using Tapatalk

[bonoz]

Yeah same! Any advice on how to check for short circuits?

[bonoz]

Either battery or alternator are no good. Should be 12.6V off and 13.6 to 14.5 with working alternator engine running. Worth checking the battery and engine and alternator ground connections before buying the battery or alternator.

Is the battery light in the cluster on when you switch ignition on and then disappears? Or does it never come on when you switch ignition on? If it is always on a bit dim, then the alternator is the problem, I once had that on my M3, 2 alternator rectifier diodes were bad. Changed the cpl. rectifier and all was good.
If the light never comes on, then the alternator does not start charging. Change the bulb in the cluster. Check correct wiring.The importance of having an operational warning light for the alternator (idiot light) is crucial. In most modern systems, the electrical current passing through the filament of the warning light is what energizes a circuit in the alternator to start charging.
see page 1230.0-00 charging system, from instrument cluster goes the line to D+ X6509 http://wedophones.com/Manuals/BMW/19...g%20Manual.pdf
E36-Exciter-Wire-Problem https://www.bimmerforums.com/forum/s...r-Wire-Problem
https://www.bimmerforums.com/forum/s...ng-Need-advice!

If it sat for two years, I suspect the battery is the issue.
Check the fluid level, add distilled water as required.
Then trickle charge the battery for at least two days. Check voltages as described above once again.

I have never heard of a bad battery causing a car to die while it is running. You checked the electrical system for short circuits?

After all the stress on it, the battery will likely need replaced too. But something else is definitely going on here.



Sent from my SM-G975U using Tapatalk

Yeah same! Any advice on how to check for short circuits?

Wanted to provide an update.

The battery light in the cluster does come on when ignition is in position 1, and then when you start the engine, the light goes away. So I'm guessing this rules out an alternator issue?

Further, when car is off, the battery voltage is 11.86 V. This is same at the alternator. Suggests that perhaps the internal wiring of the car is intact?

When engine is on, this voltage increases to 12.56 V. This is same at the alternator. And this is the new alternator. Shouldn't this be 13.5 something?

So I'm not sure what's going on. Is the engine just not providing enough power? I also replaced the belts. Could it be the pulleys? Or could it be a fuse?