alternator or voltage reg?
 

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. :eek:

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

Thanks!

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

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

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

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.

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

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

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.

LOL...it's the intake system in a BMW E39 M5. :cool: