Charging Problems

On my 1989 300E I have a problem when the car is running. The car runs fine in the begging, so I turn on the a/c and everything is well. I was driving for about 20 min and all the sudden the ABS and exterior burn out light warning lamps came on; then the car started to run rough. This happens only when I am at a stop. When I turn the a/c off the car is running great and the warning lights turn off.

I called my mechanic and he said that when the car was in the shop a few days ago he checked the charging system and it checked out fine. He also mentioned to me that the battery might need to be changed, so I should put a battery charger on the battery and see what happens in the morning.

One other quick thing, I notice when getting to a stop the temp of the car was between 80 - 120 degrees C. When the car is in motion the temp drops between 40 - 80 degrees C. Is this normal in hot temp.

Also could both of my problems be related to the high temp we are getting in Toronto. Today it was at 34 degrees C. and with humitity it was around 45 degrees C.

Your help would be great

Thanks

[Arthur Dalton]

Do a search on "OVP relay"

What is an ovp relay and what does it do?

Thanks

[Arthur Dalton]

Use the search feature...

The OVP relay was replaced a month ago. Could this be a battery problem?

[mbdoc]

The 1986-89 300E's have an alternator that is too small. Only 65-70A max output.

Sounds like you are having an under-charging problem. You need to watch voltage while driving. Radio Shack offers a cigarette lighter volt meter.

WE always try to up-grade those cars with the 1990 & later alternator (80+A).

All you need is the later alternator (Bosch AL66X) & wiring harness 124-542-45-26 ($62 LIST new). OR get the harness from a bone yard!

Could all these problems be caused by the extensive heat we have been getting, making the A/C work harder. This is the first time that this under charging is happening.

I upgraded my alternator to an 80 amp from a 70 amp and I changed the wiring harness also as was suggested and my problem went away.

Thanks for all your help.

What great people we have helping us in our problems. Keep up the excellent work.

Fab