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mysterious charging system failure


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My 92 STS' battery voltage is tumbling everytime

i'm idling or even at rpms<2000. It's happening

even when i'm running nothing more but the heating

ventilation and keep the engine idling, then in

minutes the voltage is displayed at 11,5 Volts, still


When really no accessory is on, it's charging a little,

and especially at rpm>2000 it's all OK, climbing to

13,5 Volts and beyond.

The scary effect is that in mid-drive, being below

2000 rpm, the headlights' brightness goes down

together with the voltage drop. As soon as i run

it at higher rpm they go bright again...

Big mystery is, both the generator have been

already swapped (ACDelco remanufactured alternator CS144 incl. regulator, and a new battery), without doing much to solve the problem.

Discharging of the battery while parked does not seem to


92 SevilleTS

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Did you replace the alternator and the battery because of the same symptoms? What happened?

The old battery (a Delco Freedom 72) was badly to stay

charged during parking/storage. After 2 days of no use

it was discharged to the point of not being able to start.

But the poor charging symptom was there all along and

i think it didn't have anything to do with this battery


The charging problems just started out of the blue

sky when one day i noticed the headlights to have

lower than normal brightness, then it was noticeable

every time again.

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Maybe try cleaning the battery cables really good, seperate the two positive cables and clean, also clean the terminals on the battery itself.

Life is too short to grow up!

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This sounds like the classic symtoms of a bad ground connection(s) to me. There are several throughout the engine compartment, and throughout the car for that matter. Check all of those under the hood first, particularly the ones from the engine to rad support. I think this one is notorious for "dissappearing" for some reason. Keep in mind this post is a recollection of things read in past posts, you may not even have a rad support ground on your specific model, but the theory is the same. They can break, corrode, loose connection, or just be removed during service and forgotten.

Never underestimate the amount of a persons greed.

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