A/C Problems Need Help

[SpiredFate]

I've been trying to diagnose an A/C issue with my 2012 Mustang GT for some time now and all the things I try have had no results. My A/C will not come on. I replaced the A/C compressor & condenser about 2 years ago. I have replaced recently in an effort to fix the issue: the A/C Clutch Cycling Switch as well as the radiator fan. It has optimal Freon levels, all related fuses are good and the A/C relay is functional, and bypassing the relay causes the A/C to work fine. The radiator fan comes on with the manual climate control set to A/C as intended. If anyone can point me in the right direction with this, that would be grateful.

 

[DieHarder]

Recommend following troubleshooting procedures. I'd start w/Diag/Testing and go from there. If you still can't figure it out I'd try a good mechanic or take it into the dealer. Should be able to track down the culprit fairly quickly.

Ford Workshop Service & Repair Manuals - fordrepair.info - 2011 Mustang Climate Control System climate control system- general information and diagnostics

Ford Workshop Service and Repair Manuals, 2011 Mustang Workshop Manuals Electrical Climate Control System Climate Control System- General Information and Diagnostics

iihs.net

 

[Afolly]

It sounds like you've done a thorough job diagnosing the issue with your 2012 Mustang GT's A/C system. I just feel it would be nice for you check the A/C Pressure Sensor

 

[stevbd]

OP, did you replace the expansion valve? Top of the firewall behind the engine. It can get stuck either open or closed and should be replaced with any compressor or condenser change. Cheap and easy access on our cars.

 

[JC SSP]

A sticky or blocked expansion valve will show when you attach your gauges (high and low side readings). I suspect something electrical. Could be relay, switch, etc. Have you tried jumping (bypass) the compressor to see if it engages?

 

[SpiredFate]

A sticky or blocked expansion valve will show when you attach your gauges (high and low side readings). I suspect something electrical. Could be relay, switch, etc. Have you tried jumping (bypass) the compressor to see if it engages?

Yes, I bypassed the compressor relay and the compressor engages while bypassed. I had taken it to a shop to try and have them diagnose the issue and they actually tried telling me the compressor was bad and needed to be replaced…where I proceeded to show them that it actually works fine when the relay is bypassed. I swapped the relay for the fuel injector relay and verified that the relay itself is not the problem as it also functions properly, so something is preventing the relay from triggering. I ordered an OBDlink cable for my laptop where I will use FORScan to attempt performing a dealer level diagnostic test on the system. Still waiting to get that.

 

[JC SSP]

When you bypassed the A/C it worked as intended (cold) and the gauges read the correct reading?

Someone else had mentioned psi switch. Try that…

 

[SpiredFate]

When you bypassed the A/C it worked as intended (cold) and the gauges read the correct reading?

Someone else had mentioned psi switch. Try that…

I replaced the A/C Clutch Cycling Switch otherwise known as the pressure transducer which is on the A/C lines, as far as I know that is the only pressure switch. One of the things that I have thought of is the Temperature Switch, but at this point I am just going to wait for my OBDlink to come in rather than continuing to replace things that are not actually the problem.