A/C with PFC?
Yes it causes AC problems with some models more than with others. The touring seems to have less problems with the PFC and the R1s more. There
is a home made fix that allows the AC to function
totally without ECU control. I posted it a while back.
is a home made fix that allows the AC to function
totally without ECU control. I posted it a while back.
Rotary Enthusiast
Joined: Feb 2001
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From: Montreal, PQ
It may depend on the model of PFC. Although I am not sure on this one. Mine works obsolutely flawlessly. It takes a few days to get the idle perfect. and a few days of running a/c to get it running right with a/c on. same with an electrical load.
John, just get one, trust me! your car will drive like a champ.
John, just get one, trust me! your car will drive like a champ.
PFC AC FIX:
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 attemp
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.
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 attemp
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.
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