alternator or voltage reg? - PeachParts Mercedes-Benz Forum

Glen · #1 02-12-2008, 11:01 PM

Car is a 1990 190E 2.6, 5-speed.
177K miles, unknown if alt is original or not, however, I changed the voltage regulator 6 months ago when it failed causing a dead battery.

Today's symptoms:
battery and ABS idiot lights came on

Voltage at battery with engine on: 13.9V

If I disconnect the negative terminal,
voltage reads ~10V at idle, increases as RPM goes up with peaks to ~16V.

So, does a defective voltage regulator (remember it's only 6 mo. old) make the most sense or is the alternator also suspect?

Thanks!

redcoupe · #2 02-12-2008, 11:20 PM

If you just replaced the regulator it could of just masked the alternator being bad and now its taken out another regulator.

Glen · #3 02-13-2008, 01:22 PM

Thanks, that sounds reasonable. I'm still tempted to try another VR since they are cheap relative to a complete alternator.

bobs · #4 02-13-2008, 01:34 PM

Why don't you pull the alternator and have it bench tested?

hey_allen · #5 02-13-2008, 01:55 PM

You should be able to test for wiring problems (ie: open/shorted winding, or failed diodes) with a meter, if you don't have a shop around that can bench test it.

No real point in throwing another regulator in it though, unless you suspect that you had a poor quality one that failed on it's own.

bobs · #6 02-13-2008, 02:06 PM

Glen, this is totally off topic, but what is that on your Avatar?

Glen · #7 02-13-2008, 02:09 PM

Quote:

Originally Posted by bobs

Why don't you pull the alternator and have it bench tested?

Because that's the logical, smart thing to do.

I sort of want a quick solution because it's my daughter's car and I don't have a lot time to work on it until the weekend. A VR I can r&r in about 20 minutes...a complete alt. swap isn't much longer. To get the current alt. tested would mean I need to pull it, take it somewhere, etc...I guess I'm just being lazy.