Air Cond issue/ high revs - United Bimmer Community

**elsabor67** · 04-16-2007, 03:58 PM

Hey all,

I ran into a problem today that has left me really stumped. I went to turn my ac on my 89 E30 and the revs shot up from idle (750) to 2500-2800 rpms and wouldn't come down until I shut the AC off. If someone has had this problem, could you please give me some insight as to what to look for? Thanks

**Exilion** · 04-18-2007, 04:53 PM

I've had similar problems with mine. My a/c would just cut on and off prematurely resulting in constant shifts in rpms going up to the 1500-2100 range. So far I've found three common problems with a/c's which are hose leaks, compressors, and clutches. Now if your a/c can still cool the air and it's just running up the rpms it's probably a clutch problem.

However this is just what I've found online, I'm waiting for my service manual to look it up so I can't really say.

**xsperf** · 04-18-2007, 05:46 PM

all i know is if it is taking too much power from the engine it means its overcharged, but since you probably havent fooled with it at all, that may mean, like stated before, you have a leak

**theSMELSINATOR** · 04-18-2007, 08:17 PM

can you hear the engine work harder or is it just the needle? my initial thought was that it could simply be an electrical problem.

nick_318is · 04-19-2007, 10:18 AM

On mine when i turn on the ac i gain a few more revs but nothing very noticable, so to an extent it is normal but you have your revs going up way more then needed and I don't really have any idea.

**Bibolt** · 05-21-2007, 06:43 PM

Hi
I had some problems (many problems) with my 320i e30 1988's ac.
one of them is that when I turn the ac on the rpm drops by about 200 , and when i drive the car is ok, but when i stop for a traffic light the car dies bcz rpm is getting too low.

first I have adjusted the tps screw, the car was ok when turning on the ac, but when i turn off the car and switch it back on with the ac switched of the rpm got to about 1500 - 2000.

so i changed the fuel pressure regulator and it's hoses, and this problem was fixed.
p.s i had to re adjust tpsafter changing the fuel pressure regulator.

Hope this wld help.

**John L. Harrell** · 09-01-2007, 02:44 PM

I copied what I sent to Exilon. Hope that this gets you in the right direction.

John

I guess you have not resolved the idle problem?
A few things to check.
Is the compressor clutch engaging and is there a load, charged a/c system?
Is the throttle switch working/ properly adjusted?
What ECU is installed. ECU's prior to the 173 run 1.1 firmware which exhibits a jerkiness when the throttle is closed and compressor disengages. Swap ECU's to another of the same series or higher - 351,380,525,526.

Best thing for that Haynes manual is for it to be lost.
Do not dick with the idle mixture set screw or fuel pressure. You will screw up what is right. The ECU will be working overtime to compensate for what you are dicking with.
There is no idle speed adjustment for A/C operation. You are not working on a 68 Chevy!

Happy hunting

**elsabor67** · 09-02-2007, 04:47 AM

Sorry, I completetly forgot about this thread. I did get the problem fixed. It came out to be my Throttle Pos. sensor AND my ECU. I have a 153 ECU w/chip and when i swapped the ECU to a 173 my check engine light flashed me the code for the tps.

When I replaced the TPS and set it to where the old one was set, it was still revving hard and now without the ac on. I borrowed another 153 from a buddy of mine and the revving went away. All I have to do now is get the AC serviced. Thanks for the help and advice guys