Electrical Battery Issue!!!!

[MannyCooks]

Sup guys,

So I've been having this electrical problem with her for almost a year already and I've taken her to 2 mechanics and no one can find out the issues. So once I fully charge the battery (Autozone) the car turns on and runs for maybe about an hour until it completely dies. No power whatsoever. Completely dead. I thought it could be an alternator issue but its not. Thought it could be the alarm system so I took it out and still the issue continues. Any idea guys?

Thanks

Manny

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[slum dog]

You only get a hour from a fully charged battery, how was the alternator tested?
Does the battery light come on with ignition and go off when the car starts??
I had a battery 12.6 volts off, while car running 12.9 /13volts but once I turn anything on that demands power like aftermarket sound or head lights the battery would drain dead.
Changed regulator brushes bumped it 13.7 14.2 depending on rpm.
No issues after that

[dnguyen1963]

Correct me if I'm wrong, but I remember reading somewhere that in the early cars (pre-1986?) a damaged SI/instrument board would prevent the battery from being charged.

[slum dog]

Correct me if I'm wrong, but I remember reading somewhere that in the early cars (pre-1986?) a damaged SI/instrument board would prevent the battery from being charged.

The charging system works with the battery bulb on instrument board so I believe you are correct.

[be34st]

The charging system works with the battery bulb on instrument board so I believe you are correct.

I'm having the same exact problem with my 84 318 that has been M20 swapped. I inspected the wiring and everything looks to be in working order.

I noticed a day ago after charging the battery up, starting the car, and letting it run, that the tach is dead. I obviously have an issue with the instrument cluster and wonder if my electrical/no-charge issue is related.

OP please share in progress you make with this issue. Thanks.

[e30davie]

yah i would be curious to know how the alternator was tested. Should be 12V -ish when not running, and over 13v when running.

If the SI board or whatever is playing silly buggers you should be able to bypass it wire the alternator straight to the battery, you just need to put any old bulb (NOT LED) where the bulb goes, as its the exciter.

An auto electrician worth anything should have been able to diagnose this issue in about 5mins.

[jeffnhiscars]

How do you test alternator voltage output with the car not running :)

[dnguyen1963]

How do you test alternator voltage output with the car not running :)

You can...just get 0V that's all.

[jeffnhiscars]

You can...just get 0V that's all.

Well...that's not really a test is it :)

[reelizmpro]

You can...just get 0V that's all.

LOLLLL that's rich.

[reelizmpro]

Sup guys,

So I've been having this electrical problem with her for almost a year already and I've taken her to 2 mechanics and no one can find out the issues. So once I fully charge the battery (Autozone) the car turns on and runs for maybe about an hour until it completely dies. No power whatsoever. Completely dead. I thought it could be an alternator issue but its not. Thought it could be the alarm system so I took it out and still the issue continues. Any idea guys?

Thanks

Manny

What is the year and model? How did you check the alternator? if you have a pre 86 cluster, a faulty battery bulb or bad contacts on the instrument cluster could cause the alternator to not charge the efficiently.

[slum dog]

How do you test alternator voltage output with the car not running :)

Well my buddy has a home built rig set up, basically its just a bench vise modified with adjustable brackets so most alternators bolt on.
It then runs on a belt to a air compressor motor which turns at 850 rpm and has you press down on the foot pedal it picks up rpm to around 2500

I also seen those old toppies us a heavy duty drill.

[slum dog]

I'm having the same exact problem with my 84 318 that has been M20 swapped. I inspected the wiring and everything looks to be in working order.

I noticed a day ago after charging the battery up, starting the car, and letting it run, that the tach is dead. I obviously have an issue with the instrument cluster and wonder if my electrical/no-charge issue is related.

OP please share in progress you make with this issue. Thanks.

If the SI board or whatever is playing silly buggers you should be able to bypass it wire the alternator straight to the battery, you just need to put any old bulb (NOT LED) where the bulb goes, as its the exciter.

You could do what he says