Justin311

Heres the cirucmstances, hoping somebody familiar with the FD AC control system can assist me:

Purchased the 1993 R1 from previous owner, during the winter, who had added a electronic water temp gauge. The sender for the electronic gauge was installed cheaply (IMO) as he tapped inline to (what I beleive is) the heater (!) hose near the upper firewall, and then ran a bare wire around the body of the sender and attached it to the firewall for a ground. Not what I would have done - I would have tapped into a main coolant line, or into the block, and then properly grounded it (or at teh very least soldered it).

The car had a stock ECU when I purchased it, and I installed a PFC. I was warned that R1s had port installed AC systems, and that sometimes the PFC would cause the AC not to work. Well this week was my first chance to use it...and I was pleasantly suprised that it worked! For a while

After running around with it on for a while, I noticed that the air temp was increasing rapidly and then the AC completly shut off. Then sometimes it would come back on. The LED was still lit on the AC switch at all times. To start troubleshooting, I noted what I was doing when the AC would die out:

1) Started car. Ambient temp ~90*. Turned on AC with "vent" and "fresh air" settings. Temp dropped like it should.

2) Tried pressing "recirc" to get it a bit colder. Possibly coincidence, noticed that the temp shot up (i.e. AC turned off).

3) Possibly another coincidence, noticed that right when I switched to "recirc", my digital aftermarket coolant temp started dropping from what it normally reads (180*) to "Lo" at a RAPID pace. Probably 5* per second.

I tried switching controls back and forth to get the correct sequence to make it come back on again. I haven't been able to make sense of it. One time when I turned the temp dial from cold to hot then back to cold, the AC kicked back on. Don't know if its a coincidence or not.

I also started watching the temp gauge more closely and it will kick on and off (meaning giving the proper reading of 180* down to the "Lo" reading and bouncing back and forth) without reason.

So I went from my initial assumption that the PFC was messing up something to the assumption that somehow a valve is triggered which is somehow (partiall) bypassing hot coolant into the heater core, heating up the AC air before it gets to me? But I'm not sure how it all works.

Can anybody give me some ideas to troubleshoot? Any way to "lock" that valve (wherever it may be) to test my hypothesis?

What exactly are the symptoms of the PFC messing up the AC? Does the AC have its own ECU as well or is it all run off the main ECU? Obviously my next step is to plug the stock ECU in to double check, and reinstall the temp sender (any links to the best place to locate it?)..but haven't had time to work on it yet. Any ideas or links to threads would be appreciated!!

7racer

this sounds like the PFC AC issue

mine initially worked but then during a rebuild, stopped working. Ended up fixing a ground.

This is a good thread to try to troubleshoot it. It can be a big PITA as there isn't one "easy" fix

https://www.rx7club.com/forum/showthread.php?t=435420

rynberg

It sounds like PFC type behavior to me as well.

Justin311

Thanks guys, I'll check out that thread. Honestly I'll go back to my stock ECU during the summer months just to have my AC. I've turned into a wuss! :p

Busted7

It might also be the low pressure safty switch built into the compresor! It will kick it on then pressure drops when it starts to pump and it shuts off!

cewrx7r1

iTrader: (2)

Go to the PFC forum and search on the problem. It was discussed recently, AGAIN! The latest and best fix is using a relay to prevent the floating ground problem.

Justin311

Yes I read thru that whole thread and the relay seems the best solution and pretty straight forward. I am fairly confident the PFC is the problem since I was able to get it to kick back on messing with controls (blindly). Now that I know its the fan switch ground that is the problem I will troubleshoot somemore tomorrow, and solder in my relay assuming I find thats it! Thanks guys