I have been fighting a problem for a few hot weeks now with my a/C. until recently the problems were mechanical. as long as I had the car now (a few months) the a/c hasn't been running.

I recently discovered when I turn on the a/c the Power FC sends the wrong signal to the CA relay. the results in not turning on the compressor.
the relay needs the ECU to ground. the Power FC sends it a +5 vdc signal... and not all the time.
it turns OFF the compressor if you go to fan setting 3 too quickly and never sends out a signal on fan setting (blower) 4.
has anyone had any similar problems?

 

After searching I find others have had similar problems with the setting on the fan switch where things will work correctly being the only difference from car to car.

I see for some the fix has been to bypass the ECU all together.

I don't want to do this.
for me Im going to wire up a little 5V relay and an LED. the relay will use the signal from teh PFC to turn on the compressor in fan setting 1-2-3 then since fan setting 4 is not working and I would like it to , Ill wire a bypass. basically, the ECU will run the compressor in 1-2-3... in 4 though Ill bypass it all together and run another relay doing the chuck MOD.

This way it'll basically run just like stock.

 

Forcefed, I have the same problem. I talked to Dave @ KDR and he said the a/c board behind the dash was bad. He said to replace it or fix it.

 

Did you do this?
Did it work?

why would a bad a/c board work with the stock ECU and not the power FC?

I could see if I always had this problem.
It seems PFC specific. let me know if you find the AC board was teh probelm. hell let me know if you find it's not.

 

I seem to have the same problem. All I did was pull the ac relay out from the front of the car and put a wire from the lower left to the upper right side connectors. These connectors are where the relay plugs into. Now my compressor comes on when I turn on the fan.

 

Are you sure?
from the looks of the schematic, your compressor is always on. Whenever your engine runs and the pressure switch on the HP line is happy, your compressor should also be running

 

On another note I tried putting a 5V realy across teh ECU signal to turn on teh compressor as described above, no good. It's only a 20mA relay and the ECU 5V output was not enough to power it.