W124 '95 E300D Idle Surging with A/C On
 

Hi everyone,

I have been researching this problem for a long time and can't seem to figure it out. I've searched and searched and haven't found a solution.

When my A/C is on my engine surges by a few (200-300RPMs) up and down, more of a pulse really. If I turn off the A/C it idles just fine, no pulsing...

Any suggestions as to what can be causing it and how to fix it?

Thanks in advance!

Check the voltage, my voltage-regulator was going bad and cycling/surging a bit, the idle followed.

my w210 did this and it took me a while to find that it had too much freon pressure in it and was momentarly shutting off the a/c compressor when it hit a certian psi.

Babymog, I replaced the OVR a while back and it still surges. I haven't checked the freon pressure but I doubt it's too high, it's probably been a few years since it was filled.

I replaced a few deteriorating vacuum lines tonight and that didn't help.

Any other ideas anyone?

Thanks!

I've been thinking about the voltage idea a bit more and I think there might be something going on.

When I turn on my headlights the check engine light comes on, occasionally the rear defroster light will blink when turned on, and driving home tonight I had a hard time seeing the road, the headlights seemed a bit more dim than usual.

Since I've replaced the OVP, where do I go from here to determine if it is a voltage issue?

Take the car to Autozone or the like. They'll do a free battery and charging system check. Didn't say you had to buy the parts there.

Might just buy a new voltage regulator, swap it in if you don't know the age of the current one. The lights blink on the rear def when the voltage drops too low.