Rough Idle with ABS Light On?
 

My 1989 190E 2.6 is hard starting and runs rough idle when engine is cold. Once the engine is warmed up the it runs fine but every now and then the ABS light will go on and the car starts to idle rough again. The battery also dies out often and doesn't seem to charge properly. I already replaced the alternator brushes 3K miles ago. Can someone please advise?

Do you have a voltage-ohm meter(VOM)?. If so, do the following:

- Start car - leave all accessories off
- Set VOM on 20 scale - DC
- Place neg. prong on neg. terminal of battery
Place pos. prong on pos. terminal of battery

What kind of readings are you seeing?

Did you buy an after-market set of brushes or Bosch? Alot of the after-market stuff is junk. Was it doing this before you changed brushes the first time?

With new brushes, you should be seeing 13.8v - 13.9v at idle on first start-up in the morning.

As a follow-up to my previous post, check out what Steve Brotherton had to say in this post:

http://www.peachparts.com/shopforum/tech-help/12213-alternator-question.html?highlight=ring

Check the voltage protection relay. These can develop dry joints and when they play up the power to the ABS and fuel computers is cut.