Hi all,

Completely dead battery, it happened suddenly like that last thursday without apparent reason. Recharged the battery but it was completely dead again by friday. Removed the glovebox and trunk light bulbs just to be sure, no changes. Swapped the battery with the other car, same thing.

After I've read some posts on this forum, I used a multi-meter and found that I'm constantly draining 1.6 amp from the battery. By comparison, the standby current drain on the other 850 is about .025A (25mA)

By your suggestions, I removed the fuses one by one and measured the current drain in order to isolate the faulty circuit but again no changes.

In desperate, I've separate the 3 wires bolted together on the positive battery terminal and found that the 1.6 amp current drain is coming from the big wire, the one that goes to the starters solenoid.

Could the solenoid gets leaky after all those years? Is there something else that I could check in this area? Cranks perfectly otherwise but the starter ass'y is original, 22 years & 188K on the clock.

Thanks guys
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Norm

Now that the battery is charged, start the engine and check the voltage from the big wire, around 14.4V. I would think that the voltage regulator has a problem.
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Keeping it running is better than buying new

I finally disconnect the big wire terminal on the alternator to check the current leak and it stopped right away. I have no more doubt now, the alternator is the culprit.

Now, I'd like to determine if it's only the voltage regulator inside that is defective or its the whole alternator ass'y.

Any ideas?

--
Norm

Nothing about the alternator is easy!

I would take the black cover off the alternator and see if anything seems amiss - black scorch marks, gobs of magnetic dust from the brushes, ...

Sounds like your brushes are worn, so you should at least replace the VR. If you drain a quart of antifreeze and remove the upper radiator hose, the rear of the alternator can be easily worked on.

Remove the wires. Using a phillips screw driver, remove the black plastic cover. Same screwdriver can remove the VR.

I didn't remove the radiator hose and it took me twice as long as it should have, but the alternator bearings never made any noise so it stayed in place.
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Keeping it running is better than buying new

Nothing about the alternator is easy and it's true. Not much room to work around.

As per your suggestion, I removed the the radiator hose and it helps a lot but the only hose that is in a way all the time is the one coming from the A/C compressor and goes the the dryer I believe. Impossible to remove this one.

I've been able to remove the 3 little screws that holds the cover in place but I've been unable to remove it entirely from the alternator, it hits the intake manifold. I've unplugged the thermostat sensor wire but it didn't helped me much,
no access to the voltage regulator. According to a friend of mine, the brushes and
the rotors copper contacts should be worn-out after all those years of usage so it's a good move to replace the alternator anyway. I've ordered one and expecting it early next week. Bad timing, I just replaced the power steering pump a month
ago and I'll have to remove it again to replace that alternator. aaarghh

Thx guys
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Norm

Did you confirm that it was the alternator drawing that spurious current, maybe a shorted alternator diode ?

Bill

I've checked and I have 13.65V and it doesn't go any higher even if I rev up to 2K

I think I used to read that we can replace the voltage regulator WITHOUT replacing the alternator. Is it true?

I used to replace the alternator on the other 850 years ago, big job and I'd like to avoid that if it's possible

Thx
--
Norm

Hi Norm,

Good job narrowing down the culprit.

That Red wire goes to the starter AND the Alternator.

I dunno how hard it is to reach the terminals so you can maybe unhook one

to see which one it is. My guess is the alternator.

Bill

Hi Bill,

There's 2 other terminal connectors that are bolted on the big one, the one that goes on the battery positive post. There's one terminal connector with a single wire on it and an other one with 7 wires crimped together, 6 red and 1 yellow.
The current drain is coming from the BIG wire, not those ones.

Are you sure that the big red wire is going to both starter and alternator?

According to KlausC, I should read 14.4V but I have only 13.6V and I'm starting to believe that the alternator is defective and like the starter, it's the original one.

--
Norm

The Big red wire goes to the starter and continues to the alternator.
From the wiring diagram it looks like the the junction might be at the starter terminal. The starter takes maybe 200+ Amps and The Alternator might charge 80+ or so amps so they are the biggest +12V wires.
Can you get a look at the setup at the starter terminal? If there's two wires
then you remove the one to the alternator and see if your unwanted current drain
disappears.

Plan B take the heavy red wire off the alternator to test.

Also look for corrosion or junk on the starter terminal lug that can act as a resistor.
If you pull the wire/s off the starter lug measure with your ohm meter
from the starter terminal to ground It should be open/ No resistance.
If you see some resistance then the starter/ solenoid has a problem causing unwanted current flow.

Is the car in the salt belt?

FYI your battery should measure 12.6VDC with out the engine running
Charging 13.65 seems a little low 14.0 is about right
14.4 is too high and you'd be losing filament bulbs too fast.

Good Luck, Bill