Please HELP!!! Compressor cycles at idle

mooseknuckle3835 on Fri April 20, 2012 9:58 PM

Year: 93
Make: mazda
Model: rx7
Engine Size: 383
Refrigerant Type: r134a
Pressure Low: 30
Pressure High: 200
Country of Origin: United States

I have a problem that no one seems to know the answer, so I turn to the internet for your help. I have taken it to 5 different shops with no luck. Ranging from the guy who built my Harness and lines( who has done 50+ of these swaps), my tunner, and 3 different dealerships. For starters I have a 93 rx7 with a ls6.

full scratch built harness including a/c wires and relays
Used GM compressor from an Fbody camaro
02 Camaro SS ecu
custom lines for the swap
new condenser
new drier
Replaced the old GM pressure switch with a new one (no change)
new expansion valve
Stock mazda thermo switch
Stock mazda control panel.
Flushed Stock Evap core

My A/C when on at idle continuously cycles on-off-on-off-on etc. Until i have just the slightest bit of throttle it performs correctly. I have tried to bypass the logic control to make sure that was not the issue by jumping the relay, I tried jumping the Thermo switch by connecting the two wires both with no change in results. When we control the computer by a scan tool it will stay on like it should or off when signaled. The moment we unplug the can tool it starts to cycle again.

The A/C blows cold when driving as it should but once I come to an idle it cycles continuously. Before I buy a new compressor I wanted to get some insight from the Guru's since I couldnt get any help locally.

Everyone says it acts like its low on pressure but its not. This is a common swap and I am running the same parts and pressures as everyone else. I am so irritated with the car at this point I am weighing my options of a complete partout!

JJM on Fri April 20, 2012 11:03 PM

Not having any idea how this whole mix 'n match is setup... is the '02 Camaro PCM in any way controlling the compressor? Any codes? The V7 should not be cycling.

Where is the pressure switch installed, in relation to the new lines?

I can't imagine this system operating properly with a TXV when it was designed for an OT.

Are you able to pull any scan tool parameters from this thing?

Might be best to just go with a simple CCOT setup, or thermosatic switch, bypassing the PCM controls altogether. The 02 PCM was just not engineered for your setup.

Joe

When considering your next auto A/C purchase, please consider the site that supports you: www.ACKits.com

mooseknuckle3835 on Fri April 20, 2012 11:56 PM

This link might give you more insight on what my system looks like. There are hundreds of people using this setup without any issues.

http://www.norotors.com/index.php?topic=1119.0

Edited: Fri April 20, 2012 at 11:57 PM by mooseknuckle3835

mooseknuckle3835 on Sat April 21, 2012 12:01 AM

Quote
Originally posted by: JJM

Might be best to just go with a simple CCOT setup, or thermosatic switch, bypassing the PCM controls altogether. The 02 PCM was just not engineered for your setup.

When considering your next auto A/C purchase, please consider the site that supports you: www.ACKits.com

At this point I am willing to do anything. Any insight on the best way to run it from CCOT or thermosatic switch would be great. I still have the original Thero switch installed in the car but it does not interface with the PCM i dont believe. The only wire feeding into the relays is the AC command.

mk378 on Sat April 21, 2012 10:15 AM

This sounds like the PCM is deciding the idle speed is dropping too low and following its program to cycle the compressor off to avoid stalling. You could do what JJM suggested and bypass the PCM entirely. Leave the PCM input connected so it still knows the A/C is on and will boost idle air in anticipation of the extra load. But connect the relay coil to the input side and leave the PCM output unused. If it's using a PCM-connected sensor for high pressure cutoff, that will no longer work. You should alway have an effective high pressure cutoff to prevent hoses from blowing out. The stock Mazda dual pressure switch will do that.

Variable compressor OT systems used GM's special low pressure switch that cuts out at 10 psi. This pressure will never occur during operation, the switch is to protect the compressor in case of total leakout of the refrigerant or extremely cold weather. The Mazda dual pressure switch on the high side will serve the same purpose. Also you should not need a thermal switch at all, the compressor's pressure control will prevent freeze-up.

Edited: Sat April 21, 2012 at 10:29 AM by mk378

James89dx on Sat April 21, 2012 3:11 PM