Tom Smith

So my AC runs on all levels, but, settings 1 and 2 blow cold, 3 and 4 the cooling shuts off and just pumps the ambient temperature. Recycling or non settings don't change anything either.
Anyone have this issue? Any suggestions on where to start?
93 touring. Compressor works fine, just filled with freon, I'm stumped.

cr-rex

iTrader: (114)

https://www.rx7club.com/power-fc-for...ition-1151025/

try this

Tom Smith

I'll give it a shot, but my fan isn't the problem as stayed in that thread you linked. All cycles have fan action, but 3 and 4 stop "cooling".
I've run into the fan issue before and fixed it, hopefully this drop in cooling is somehow related to that relay.
My Commander is on its way to John's to get fixed, so it'll be a few weeks before I can try.

cr-rex

iTrader: (114)

Can you confirm the compressor is disengaging with speed 3 and 4?

Tom Smith

Not to sound ignorant, but how would I do that?
When I switch from 2 to 3, the vents change from cool to "stale" ambient temp air, as if the fans are just pulling thru outside air. From 3 to 2 the smell dissappears and it begins to get cold again. Not sure how to tell if the actual compressor turns off or not. 🤔

Pete_89T2

iTrader: (4)

You'll need a helper. Get someone to sit in the car with it running and have them cycle thru all the fan speeds with the A/C switched on while you're under the hood looking at the compressor and watching for the clutch engaging/disengaging.

jza80

iTrader: (32)

If you are using a Power FC, I think you are going to find that the compressor is not engaging at fan speeds 3 and 4. Basic problem is very common, one way to fix it is to install a relay (there are posts on that). In my case I was able to resolve it by installing a new fan speed switch. But either way it sounds like that is your problem.

Tom Smith

I do have a power FC, just can't check anything on it because the controller is in Australia getting fixed.
CR-REX posted the link to the relay solution earlier on in the thread. Going to try it out.

DaleClark

iTrader: (55)

I had the exact same issue with my PFC. The relay fix linked above solved it. VERY common issue if you have the PFC.

Dale

Pete_89T2

iTrader: (4)

^Not just with PFC's, but pretty common issue with most aftermarket ECUs. The PFC and other aftermarket ECUs typically tap the violet wire on front (F) harness connector B1-01 to sense the A/C on or off state; 12VDC = logic 1 = A/C OFF, and 0VDC = logic 0 = A/C ON. Problem is the voltage on this line varies substantially because of resistance in the fan speed switch circuit. Ideally, it should be zero when the A/C is ON at ANY fan speed, and 12V when the A/C is OFF. In reality, you might see something between 0.5V ~ 4V on that violet wire depending on fan speed. For the ECU to work right, it typically needs to see something less than 1 ~ 1.2 VDC (that's the threshold for my Link G4+ ECU to read it as a logic 0); any voltage greater than that and the ECU reads it as a logic 1.

The fix that works well with the Link and other ECUs is to add several forward biased diodes wired in series to the ECU input that taps the violet wire. So if your diodes each have a 0.4V drop when forward biased, and you wire 8 of them in series it results in a 3.2VDC drop. When the A/C is off, your 12V is now seen as 8.8V, which is still > 1V, so still recognized as logic 1. But now if your A/C is on at any fan speed, and the highest voltage seen on the violet wire is < 4.2V, after the 3.2V diode drop, the ECU will see <1VDC and correctly recognize it as logic 0, A/C ON.