Hi. I have an 09 FX4. I had the blower motor resistor go bad, ( only blow on one speed). Replaced with a rock auto part. As soon as I replaced it the fans speeds return, but the a/c no longer functions. I have verified a full charge in the system. When I turn it on, the compressor runs for a few seconds and shut off. I don’t have a scan tool to monitor the electronic sensors. Any ideas? It’s very odd that this happened after replacing the resistor. I even got o different one from local store to verify that wasn’t the issue. Any help is appreciated. Thank you.

 

How did you verify the charge? Did you evacuate and recharge with known correct amount? When you say it shuts off, it never comes back on? Could be overcharged or undercharged? Just some ideas.

 

I recharged the system with the proper amount of refrigerant after vacuuming the system down

 

The compressor usually cycles on and off frequently. Sometimes a little too fast for some. There's an HVAC reset/calibration of sorts. Either unhook the battery for a minute or pull the correct fuse (I'm not sure which on a 2009). Replace, then turn the ignition ON (not the engine), and wait for at least one minute. Or use Forscan to reset the HVAC module.

Otherwise, probably start doing tests on the compressor and clutch.