Idle problems with A/c on - 84 Carrera
 

Hey guys,
Finally got my A/c running. Only one prob, at random while driving and let off the clutch the rpm's will drop and the car will turn off. This only happens when the a/c is on. Any suggestions ? I'm thinking vaccum hose or idle control valve. Is this correct ?

Check your base idle as well, via jumper plug B&C, if stock should be 780RPMs if chipped 880RPMs.

It is normal for the draw to lower the RPMs but not shut down,

Yes, base is in the 780 arena for sure. When i turn the ac on it drops to around 500 and when i switch gears goes to almost 0 then pops up again. Sometimes it doesn't pop back up and the engine shuts off.

BTW thanks for all your help DRACO, i got the doors squared away earlier.

Oh Cool, glad you got the doors squared away.

OK, so I assume now you have the OEM stock chip when you say base is in the 780 arena, is that when you jumper B&C? That is the only way to verify base idle. You see DME will compensate like crazy if it is not at proper base idle.

It could also be the compressor seizing, I hope not but if you remove the A/C belt spin the clutch of the compressor if it rotates smoothly or not. How is the refrigerant level, Did you do a recent A/C service?

Jim

Sorry just re-read: You did service your A/C. What did you do as far as service? Re-charge? How much did you put in? Too much will labor the compressor.

I didn't do it, i paid my porsche mechanic to do it. I'm sure it's right. He also did a tune up and i asked about the idle and he said it was good. I'm thinking it's probably a vaccum hose.

If you had a vacuum leak it would be apparent without the A/C.

I would find out how much was put in, I suspect he may have made an error and put too much.

Is your system taking R12 or R134. R12 is the bicycle type fill nipple the R134 is the Quick Release Larger type.

hmmm, r 12. But i'm sure it's right, do you think it could be a simple idle adjustment?

the reason i think it's not the r12 is beacuse it did the same think before i recharged the a/c.

It could be, if you take a piece of 12-14 gauge wire 4" long. Open your engine lid and look to the left side. If you have the OEM plastic shield held by winged screws, remove it, then look a bit forward and you will see a round relay socket that will fit the round relay in the trunk.

You will put the wire in the two holes located isolated center forward and the counter clock wise skip one and plug the other end to that hole. Start car, rev twice wait, this is your base idle confirmed. if not at 780RPMs, adjust the idle screw until it reaches proper levels, rev twice to confirm it sits at 780 RPMs, pull wire then test the A/C.

http://forums.pelicanparts.com/uploa...1285909797.jpg
http://forums.pelicanparts.com/uploa...1285910043.jpg
Image borrowed from Gerry 86 Targa Guy

Jim

Cool, i'll try it tomorrow after work.
Lemme know if you can find that diagram.

"When i turn the ac on it drops to around 500"

The possible causes are:

1. The idle switch on the throttle body is not closing at idle position.
2. The idle control valve is stuck or its winding is open.
3. The DME ECM idle circuitry is bad.
4. The idle valve does not have 12 volts to the center pin.
5. The compressor is loading the engine too much, e.g. too much freon.
6. The idle valve may be installed incorrectly.

I concur with Lorenfb, it could also be the ICV. Test: when you turn on the A/C open the lid and take a screw drive and tap on the ICV, if it clears up, it may just need cleaning and lube.

To properly test it check the OHMs per Bentley.

But I default to too much R12, I did the same thing added too much and my idle dropped to stall. Once I removed to properly levels, it was all good and cool.

Your wrench is human as such could have made an error in the fill. He had R12? Rare.

Jim