ShiftRX7

I have just realised that turning on my A/C is not giving any signal to the fans (wether to increase speed or to start); temp set on the PFC and input from the thermoswitch is ok though...any suggestion on what can be causing this?

Thanks a lot for your help.

Ciao!

Mahjik

iTrader: (1)

First, you might check how the relays trigger the fans:

https://www.rx7club.com/showpost.php...53&postcount=2

wstrohm

If you look into the engine bay from the front, on your left are four relays mounted in front of the passenger-side coil spring mount against the fender well. the one most forward in the upper pair is the Coolant Fan No. 1 relay. Its connector is "B2-01."

There are 4 connections to this relay; the wire of interest is violet with a pink stripe. This is the wire controlling the coil of the relay, by either floating (A/C off, which would show +12 volts through the relay coil with ignition ON), or by being pulled down to near zero volts (A/C on). So in order for the cooling fans to respond to the A/C switch, this wire must be at a low voltage when engine is running and A/C switch is ON.

If voltage is low, but the cooling fans are not running, the problem is in the relay or in wiring on the fan side of the relay. If the voltage never goes low as a function of the A/C switch, the problem is in the signal on that violet/pink wire.

To pull that voltage low, first the HVAC fan control switch on the console must be in a position other than "OFF," and the A/C switch on the console must be ON. If there is a problem with the resistor pack for the HVAC switch, the voltage might be low only if the fan switch is in position 1 (lowest blower speed). Other positions require the resistor pack to be good.

The ground is carried from the wiper of the HVAC fan control switch, through one of its 4 switch contacts, through a blue wire with yellow stripe, to connector G-08. From there it goes out on a white wire through connector X-25 to the "Heater Control Unit (Amplifier)" at connector G-06. It then passes through the "Air Conditioning Sensor" switch, which I conclude is the A/C power button on the console, and goes out of connector G-06 on the violet/pink wire through connector X-17, to a junction with two other violet/pink wires, one from X-26 (the thermoswitch) and one to the coolant fan relay, through X-07. So there are many places where this signal can get lost, and since this text probably won't help much, I attached a pic from the 1994 Body Electrical Troubleshooting Manual, diagram "Gb." In the diagram, the signal from the HVAC fan switch comes in at the circled "99" point. The arrow indicates current flows out from that point, which it will when A/C is active and the HVAC fan switch wiper is the current sink to ground.


Maybe this will help some...

ShiftRX7

Thank you very much wstrohm for the clear explanation! i have checked some posts (like the one Mahjik has pointed out) on that before but i never got such a clear explanation (moreover im not that skilled on the electrical stuff); ill check and see if i can figure the issue. thank you very much again for the support!