PowerFC & Air con

[Cashpoint]

I\'m running a power FC and have been trying to get my air con to work but though it has a live there is no earth. After some searching in the net I found that alot of aircon units are given an earth from the ecu to avoid the air con being on when started from cold.

Has anyone got a power FC and there aircon works?

[peterwolds]

mine works fine,couldnt tell you about the earthing

[pdtaylor18]

yes mine did work and no probs at all, I even adjusted the idle from it to adjust for when the aircon came online

[Eddie]

Min works fine as well, never messed with any erath.
My air con even works as an idle stablizer, turn it on get a good idle turn it off and it hunts like mad

[alexb]

My PFC and air con work fine together, the PFC fitment was just plug and play as normal.

My aircon will come on with the ignition if the switch is set to \'on\' beforehand, but I\'ve not heard of people modding their setup to avoid that.

[kbareham]

Mine didn\'t work after I put the PFC in my \'92 FD. No loss really - It was a good excuse to lose a little more weight so most of the aircon parts are in the loft now.


Keith

[alexb]

Really? Interesting cos mine\'s a 92 and it was fine :3Confused

[kbareham]

The blower still worked, and pressing the A/C button put the A/C light on, and the radiator fans ran, but the compressor never engaged. I did have some of the engine apart to replace the OMP at the same time as I fitted the PFC, so its possible that I disturbed something else.

I always intended to remove the aircon, so I didn\'t do any diagnostics at all. And now it\'s all removed.....


Keith

[alexb]

I guess we\'ll never know then...

[RobbieRX-7]

Same thing happened to me. As soon as i fitted the pfc, the AC stopped working. I removed the whole system, but will refit before next summer and try and get it working. Being stuck in motorway traffic on a hot day isn\'t nice.

[RemarkLima]

I did hear that the A/C swicth comes on but is activated by the fan switch which has variable resistance depending on what setting it\'s on. The PFC is much more sensitive than the stock ECU in this regard.

But IIRC you just need to get the switch out and get some contact cleaner in there and make sure all the contacts are good and it starts working again.

Best way to check is to see if it works on any of the fan settings?

[RemarkLima]

Ah, found it from http://www.fd3s.net/power_fc_install.html

Date: Mon, 03 Jun 2002 00:02:20 -0500
From: Phil (johnalla@swbell.net)
Subject: RE: (rx7) [3] AC problems

    > Has anyone ever had weird problems with their HVAC fan switch and their AC?
    > The fan switch controls the fan speed properly.  The LED in the AC switch
    > works properly.  However, if you have the AC switch on, the AC only works
    > with the fan set at 1, and sometimes works on 2, 3, and 4.  Sometimes it
    > will flicker on and off in settings 2, 3, and 4.  I can verify all this via
    > the PFC sensor check.  Jiggling the fan switch has no effect.  I\'m planning
    > to go through the AC section in the shop manual but was wondering if anyone
    > had seen this before.

After a little searching the forums, it looks like this is a PFC problem and I have been living in the dark. Chuck Westbrook posted these instructions:

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I claim no responsibility or liability for anyone who follows my instructions. You are solely responsible for any changes you make to your car. Do not attempt this if you are not experienced with wiring.

Following is details from the manuals and how to make your AC work with the PFC. Three ECU AC functions will be lost with this conversion. If the AC is on, it will not be temporarily disengaged when starting the engine. When accelerating hard, the AC will not be temporarily disengaged. The idle speed will not increase when the compressor comes on. The AC will function normally with all AC components working, except with no ECU control.

Reference materials:

Mazda RX-7 1993 Body Electrical Manual (BEM)
Mazda 1993 RX-7 Work Shop Manual (WSM)
BEM page G-12 AC wiring schematic:
At the left side it shows the AC compressor wiring;
+12V - ignition/acc switch - AC fuse - AC relay - AC pressure switch - AC magnetic clutch - ground. From the relay control coil is a Y/B (yellow with black strip) wire that goes to the ECU. It is marked as connecting point 37 and continues on the WSM B-1d schematic. On WSM B-1d, point 37 goes to ECU connector 1L. The ECU basically grounds out this connection to energize the AC relay to turn it on.

In the middle of BEM page G-12 it shows the AC control wiring; Ground - fan speed switch - AC switch - AC thermal (anti freeze) switch - and a wire colored V (violet) going to the ECU. It is marked as connecting point 36. On WSM B-1d, point 36 goes to ECU connector 1E. The ECU basically senses ground through this wire when you turn on the AC.

Cut the two wires at ECU terminals 1L(Y/B wire) and 1E(V wire). This is the bottom connector with 11 pin columns. 1L is the center pin opposite the connector lock tap. 1E is third from one end. Connect the harness side of them together thus bypassing the ECU. Leave the ECU side open. I placed snap-in connectors on all four wire ends so that they could be easily reconnected back to stock.

The cooling fans are operated from another wire that attaches to the AC relay and is not affected by this mod. In fact if you turn on the AC with the two wires cut but not connected together, the fans come on but nothing else happens. The ELU unit will still increase idle speed a little when the fans are turned to 3 or 4.