M42club.com - Home of the BMW E30/E36 318i/iS

DISCUSSION => Electrical => Topic started by: arcter on July 03, 2010, 06:27:11 PM

Title: Questions about A/C
Post by: arcter on July 03, 2010, 06:27:11 PM

Hey guys. I just got my A/C working again, using a compressor I bought from a member here (digitalme!) and a few other parts I bought from members from here and r3v.

But my mechanic ran into a problem getting power to the compressor. What it came down to is he thinks that the little electrical unit for the compressor (I think he called it HVAC something) was faulty, so he had to run an independent line from the compressor into the car to get it to work and save me some money.

Now, the a/c does work great, but I basically can't run it with the car idling. It runs the idle into the ground and really saps the power. So I mainly will use it on the highway I suppose.

Anyway, my question is basically just to see if I understand correctly. I'm assuming the little unit that was faulty basically regulates the amount of power the compressor saps, so when the car is idling it uses less (because the car is generating less power) and when the engine speed goes up it allows the compressor to use more power. So basically since I'm missing that little unit, it's just a single amount of power being sapped at all times. Am I right? :)

Thanks!

EDIT: Btw, if anyone has a name or part # for said electrical part it'd be appreciated, if I find the way it's working now to be too weird I might want to replace it.

Title: Questions about A/C
Post by: DesktopDave on July 03, 2010, 07:33:24 PM

It's  not that complicated.  There is an idle control unit that bumps the idle up a few hundred RPM to compensate when the compressor kicks on.  That's your culprit.  In older BMWs it was a separate unit, it might be integrated into the DME now and control a relay or something.

I'd figure if you replaced that it'd do the trick.  I'm in the middle of a cleanup, otherwise I'd dig a little deeper to see what you really need to do.

Title: Questions about A/C
Post by: arcter on July 03, 2010, 11:20:35 PM

Thanks Dave - if you know anything more about that it'd be helpful any time you can!
Joe

Title: Questions about A/C
Post by: arcter on July 04, 2010, 11:01:22 AM

I was wondering about the little idle control unit you mentioned, is it maybe not faulty and it's just not working because of the separate wire this guy set up?