1989 244DL,B230F,auto:

I have an issue with the Bosch 80 amp alt that was in the car. It failed a couple of tests while mounted in the car (although hot @ terminal, no output). I pulled it and tested it and it passed (more than once). I replaced it anyhow. Ground and wires seem OK too. Battery recharged and tests good too.

Car starts and runs great. Still no output from new alt. It's running on battery power only. It's curbed until I figure it out.

Instrument panel gauges all went out at same time. Fuseappeared good for that too but I replaced it anyway. WTF am I missing here. I looked up an instrument panel voltage stabilizer for the 240's, but I can't locate it. Something is drawing power when it shouldn't, or burned-out altogether.

Anyone having (or had) similar problems?

Thanks for the time,

 

As you're cranking the engine does the "BATT" light come on? It's supposed to. If it doesn't come on it might be a burned out bulb. Or it could be bad wiring. That circuit supplies excitation voltage for the alt. (the skinny red wire at the back of the alt.).

The voltage stabilizer in the instrument panel is an SCR. Three leads. It looks like a transistor, flat, black.

 

Just got home and checked it again. I hooked up the batt and cranked it. During the crank, the only thing coming on and staying on after she fires off is the overdrive lamp @ far right side of panel. All other lamps and gauges are inop. Each time I start her, she does the same thing and I reset the overdrive switch.

I don't have the meters to check wiring. Pulling the "+" cable with a new alt and fresh battery charged up and she still shuts down.

Thanks for the feedback,

 

If the BATT light doesn't come on when cranking the engine that's a big problem. The alt doesn't get excitation current and the car runs off the battery. The brake failure light, bulb failure light, and parking brake light are all grounded through the BATT light while the engine is cranking.

The most common problem is the little red wire on the back of the alt. It is on a spade connector. Even if the spade is hooked to the alt it is often a bad connection from the wire to the spade.

As a test, take the skinny red wire off the alt and ground it. Crank the engine. The BATT light should come on. If it doesn't come on then it's most likely a bad bulb.

The wire runs from the BATT light to the gray connector on the firewall and under the engine to the alt.

Post back.

 

Gotta guy coming 2-day with a meter 2 check the alt again. I may have gotten a bad reman'd alt (hopefully it's that easy). We'll check that red wire 2. Mine is a nut connection rather than a spade. But, do I need to pull the instrument cluster to get to that volt. stabilizer? Never done it, and I don't want to screw up that cluster. Could a bad alt have blown that stabilizer? It went out when the alt did.

Thanks again for the help Goose...I'll post back when I can...

 

OK....

We confirmed that the alt is now charging the batt. That red wire was the culprit it seems. We bridged it, tested it, and seems good-to-go. The OD lamp appears to have reset as it no longer illuminates after start-up.

I drove about 3 blocks down the street still with the dash cluster inop. It then powered up and appears to have reset itself. Tach and speedo are accurate. I'll monitor that for fluctuations to see if the voltage stabilizer still requires replacing.

Thanks again for thetech adviceBlue Goose...

 

It appears I had posted with success too soon. Went to move the car the next morning and she was completely dead again. It'll have to wait until my next days off before I have a chance to look at it.

 

Is there something you have in there afterrmarket that is draining the battery?
Also check the glovebox light.

 

It's got a JVC sound system that was in it when I bought it. Seems to work fine. I double-checked thesalon interiorlamp. I'll check the glovebox lamp too.

Thanks tech.