Alternator died today - PeachParts Mercedes-Benz Forum

TonyFromWestOz · #1 10-26-2004, 11:26 AM

I hadn't noticed, but my charge lamp had died (it was OK a few days ago I'm sure).
My Brake warning and disc pad warning lamps on the instrument panel stayed glowing when the engine started. After checking that I had brake fluid, I drove off and found that the indicator lamps dimmed as the engine RPM rose.
I think that the alternator is not working at idle and only working a little at higher RPM.
I tried searching, but didn't see how to combine search terms (do you type "brake warning light" + "alternator"?)
I have not had time to check out the alternator, but I put my regulated charger on the battery overnight.
My spare parts car has a working alternator, so I will swap them and have mine repaird then reinstall it and keep the spare as a spare.
Anyone wish to comment on the interesting combination of indicator lamps?
Does this occur for any particular reason?
Does anyone else have experience with this phenomenon?

tomm9298 · #2 10-26-2004, 11:51 AM

That is normal when there is an under voltage problem. When my wifes battery died I jumped it off and the ABS light was on. Replaced battery, no ABS light. Alternator reaches highest output above 2000 RPM.

R Leo · #3 10-26-2004, 11:53 AM

Together with the air cleaner mount on the turbo engine, the alternator/charge warning light on these cars has to be the DUMBEST idea to escape Germany since Festung Europa! I cannot understand why these cars don't have a voltmeter!! Absolutely criminal, IMHO.

After making a 400+ mile trip home through the Texas/Oklahoma summer (our North American equiv of the Nullabor) without a working alternator, and then shortly after that alt was replaced, having the rebuilt unit crap out without so much as a blink from the dash lamps, I installed a voltmeter.

Currently, it's a $10 cheapo sitting in the space where the ashtray used to be and wired to the connection for the cig lighter. So far everthing has worked fine but, at least when something goes awry, I'll have an inkling of an idea of what is going on instead of waiting for a stupid light.

Ultimately, I'm going to install a neato set of three miniature gauges (volt, oil pressure -I'm using this as a boost gauge & temp - for fuel temp) that I found but first, I have to build some sort of panel to hold them.

Pete Burton · #4 10-26-2004, 11:56 AM

I had a similar experience 3 1/2 years ago. The indicators behaved mostly as you described, plus some of my gauges acted very strangely. I removed and disassembled alternator. I was hoping to remachine the commutating surface but the brushes had worn it all the way down to the surface of the insulation, making that impractical. Bought a rebuilt alternator, no more problem. Weird, huh?

#5 10-26-2004, 07:16 PM

Same happen to me. Found the brushes had worn down. Changed brushes and all is well now. Can change on car without removing alternater.

Lycoming-8 · #6 10-26-2004, 11:26 PM

Some time ago Radio Shack carried a little device fit with three LED's that you can plug into the lighter port. The three lights are each a different color red, yellow, and green. The voltage is not specifically displayed, but the lights will glow in different patterns, one at a time or in pairs and infer a range of a couple of volts. Trouble can be spotted a lot quicker than via the single red idiot light most cars are equipped with. Not sure that it is still available, but the circuitry should be fairly simple to devise.

compress ignite · #7 10-27-2004, 12:27 AM

1. Electrical source (Alt/Gen/Solar Cell).
2. Voltage Regulator.
3. Storage Device ("Battery")

[My Hijack of Steve's Verbage: "Irregular Voltage/Amperage creates almost
unimaginable "Voodoo" seemingly based problems".]

P.E.Haiges · #8 10-27-2004, 12:55 PM

Tony,

Do a search on brushes. That is probably your problem and you should find enough information to them.

Changing the brushes is 100 time easier than changing alternators so do brushes first. I always carry a spare set of brushes because its a roadside repair if necessary.

P E H

boneheaddoctor · #9 10-27-2004, 12:59 PM

I am replacing my W116 ashtray (I'm a non smoker) with a panel that has Boost, EGT, and a voltmeter.

Have had my share of flakey regulators.

Cost me a stero, A tachometer and all my dash lights and a battery that was killed in 10 months from new.

Jim H · #10 10-29-2004, 10:00 PM

I miss the old ammeters, -/+, D/C, however they were marked. You could see a slight discharge at idle, then charge with increasing rpm, finally tapering off to zero as the battery eqaulized.

A voltmeter doesn't tell me much.

I got a red charge light when the serpentine belt broke!

Alternator output went completely to zero, and the light came on. So did a few other lights...

Best Regards,
Jim

TonyFromWestOz · #11 10-31-2004, 09:15 AM

Today I managed to make time to work on the car. You wouldn't believe howe many crises I have had to deal with over the past week

While the alternator in "Blue" was a Bosch unit, the alternator in "Fatmobile 3" was a Motorola unit.
I was not able to access the brushes on the Mororola alternator, so I simply replaced the alternator with the one from "Blue" (Can't beat having a spare parts car in the yard).
Before I installed the Bosch Alternator, I pulled the regulator and found the slip rings and brushes were very worn.
I will have the Motorola alternator overhauled and will re-install it ASAP.
I will overhaul the Bosch one after that too.
I will check out the alternator in "Josephine" next weekend, to determine the state of Brushes and commutator.
Thanks to all who have helped me here.
ps, I will need to replace the "Chg" light too.