Happy Sunday everyone,

I recently had the high pressure A/C line leak in which I replaced and refilled with freon (vacuumed the system, got the legit gauges, etc.). I've done this before with that known troublesome low pressure line. Everything works great when I turn the A/C on except the fans do not kick into high speed. Obviously, if I let it idle in the driveway, it will slowly get hotter as the condensor is not getting cooled by the fans. The fans are coming on but they're staying at a low speed. To ensure they can do high speed, I disconnected the water temp sensor and sure enough, they went high speed. So, it seems like whatever part of the A/C system that tells the fans to go high speed isn't working. I assumed relay but from the little I've found online, there isn't an A/C relay! How do I fix this? Any help is greatly appreciated!

Summary: A/C comes on, compressor stays on, cool air comes out, however the fans do not go into highspeed. Fans high speed has been confirmed by disconnecting coolant temp sensor. There appears to be a problem between the A/C system and fans communication.

 

My '11 switches from low to high. Fans may not go to high speed unless auto system goes into recirculation or it's a super-hot day in my Tahoe. My fans mostly run on the low speed most of the time for the A/C.

 

What temperature is coming out of your vents?

 

Did you ever figure this out?

 

​​​​​​Been noticing dumb things with my fans and the AC (running slow and actually kicking off while the AC is on and ideling when AC blower motor speed is below 40%). This hundred plus degree north Texas heat is no joke. I think it all comes down to the AI logic in these vehicles.. of course they're all computer controlled. Fans are no longer controlled with low medium and high relays they're controled with pulse with modulation. The longer the pulse the faster the fan speed, the shorter the pulse wave the slower or vise versa. There's no way to easily tap into that system to be able to control it yourself. Of course a high-end scanner tool can command fans to different speeds but you don't really want to drive around with it plugged in all the time.


One partial solution for me was to get a Diablo programmer and increase the idle speed to 900 RPM when its idling and in park increasing compressor speed so I can remote start it and have it starting to begin to cool before I get in it (this is also prevented the cooling fans from shutting off at idle). Which has worked out pretty well until these temperatures start getting above 100 and then the issue is getting air across the condenser. Works great at 40 miles per hour not so much at idle.

I've been considering a pusher fan on the front of the radiator that could be controlled with the flick of a switch from inside the cab for when you're sitting still or at low speeds. And that's how I came across your post. Although it didn't mention the pusher fans it did give me an idea. You mentioned testing by pulling the thermostat wire causing both the radiator fans to kick on at high speed. Could possibly put that wire on a relay that you would be able to break that connection with with the flip of a switch from inside the cab there by kicking on both fans high speed.