Unstable Idle with AC on

knfevg · Post by **knfevg** » Fri Mar 24, 2006 3:45 pm

I have this problem for several years now with my MK4 with AEX engine and now I decided to solve it.
The problem is that with the AC on the idle RPM arent stable. When the compressor turns on the RPM drops from the normal ~900 to about ~300 and the engine almost dies. Than the RPM playes up&down arround 1k and drops once again..and over....and over again.
When the AC is off - no problem.
When I am driving (not idle) I dont see any problem (thou it might exist but harder to spot).
I tried cleaning the throtle body and reseting the ECU. didnt work.
Any ideas?

DScape · Post by **DScape** » Fri Mar 24, 2006 6:08 pm

To me, it sounds like your battery is on its last legs (I know its been years) but the alternator is doing a good job....get your battery tested, I'm sure it's free at places...or near free

EDIT * Just noticed you're in Israel, so I can't really say if its free

I can imagine A/C to be a big drain on a battery.

Thats coming from a none expert opinion, definately an electrical problem though.

knfevg · Post by **knfevg** » Sat Mar 25, 2006 9:25 am

no, its isnt the battery. The battery is new (changed it a couple of month ago) and same the still problem. I think that it could be the alternator....I think that I'll disconnect the alternator and let it run on the battery for a few miles and see what happenes...