Yippee, A/C blows cold but fans must turn on

[AZPete]

I'm thrilled that my air conditioning works! Since I've never worked on air conditioning before, and think it works by voodoo magic, I'm amazed that it blows cold! The only problem is that the radiator fans must turn on when the A/C is on. The guy at the A/C shop says that if there is not enough air through the condenser the system will develop too much pressure and shut down. I dieted the '06 WRX wiring and now the ECU turns the fans on when the engine is warm enough. I have to find a way to connect the A/C system somehow so the fans turn on when I switch on the A/C. The ECU is wired to a relay, then to the fans, right? Is there a way to connect my Vintage Air wiring through the relay without causing a problem when the ECU turns on the fans?

[mikeb75]

yes.

you should be able to connect to the OEM AC/fan circuit. I've wired mine to a switch so I can manually turn on the fans. If you tie into Sub Fan Relay1 in the Main Fuse Box you can get one of the fans to run without changing the other ECU control of the fans.

Credit to Bob for originally publishing this information.

[svanlare]

What Mike said as I think the stock ECU turns on the the fans whenever the AC switch is on. Do you have a stock ECU? Worse case, one more relay in the system.

Do you have a wiring diagram for the Vintage Air system?

[wallace18]

Just wire a relay that is triggered by the A/C compressor clutch wire to the same wire that turns on the fan relay and you will be good to go.

[AZPete]

I have ordered a trinary switch from Vintage Air. It has a high-pressure cut-off, low pressure cut-off and fan engagement at 254 psi. My plan is to wire it into the red/blue (RL) wire between the ECU and the Relay-1's of the main fan relay and the sub fan relay. This should let the trinary switch turn on the main and sub fans, yet also let the ECU turn on the fans otherwise. Is this correct?

[07FIREBLADE]

Lol I was going to ask you this exact question. That's how I'm wiring mine up and hopefully mine will charge. I had an issue of my system not taking a full charge but I was trying to do the at home charge. Maybe I have to bite the bullet and take it to a shop to put a deep vacuum and charge my system. I think it's GR for the Ac switch and red blue for the Ac sub fan. I might be wrong I don't have the diagrams in front of me.

[AZPete]

Robert, you're right. The red/blue (RL) wire is to Relay-1 which is the slower speed. The green/white (GW) wire is to Relay-2, which is the faster speed and best for the A/C.
I think.
I took mine to an A/C shop because they have the big machine that can apply a deep vacuum to purge the system of moisture, check for leaks, find leaks, and charge the system. Since the refrigerant is bad stuff, don't let any escape. I'll do the wiring now so that as soon as I get the trinary switch from UPS, I can go to the shop again. Installing the new switch requires opening the system so I can't do it at home.

[07FIREBLADE]

Sounds like a plan. I just need to get my butt down to a shop and get my system charged. But it's currently on the back burner until I'm in paint. I hate taking the dash apart all the time. It's a real paining glad though our guess on the oem compress worked out.

On another note how did you wire up your compress clutch switch. Is yours a 2 or 3 wire connector?

[AZPete]

My donor compressor clutch has a single wire only. The donor wire comes from the A/C relay, F129. In the Vintage Air system the only wire is a black/green wire to the compressor clutch from the Trinary Switch.

[AZPete]

It's now working well, so here's what I learned. I bought a trinary switch from Vintage Air to replace the binary switch I had because the trinary switch controls the fan. I then spliced a wire into the red/blue (RL) wire that goes from ECM B136-18 to the two Relay-1's. That spliced-in wire then goes to the trinary switch. The trinary switch also has wires that go to the thermostat, compressor and ground as per the trinary switch instructions. After I had run the wires I had to have an A/C shop evacuate the system, screw the trinary switch into the drier and then recharge the system. Now the main and sub fans come on when pressure gets to about 250 psi and go off when the pressure drops. And, with the A/C off, the fans still come on when the engine heats up enough.
I'm really glad that I laid several unused wires through the console, from front firewall to rear firewall, before I upholstered it!

BTW, an error in the FSM for 2006 WRX caused me some time and aggravation: on page AC-37 Sub Fan Relay 2 = C, Sub Fan Relay 1 = E The position of the relays shown on page WI-16 is correct.