Hello everyone, In Aug 2011, I purchased a 2010 F150 STX 2WD with a 4.6 2v triton and it has been a very good truck up until last year. At 102,000 miles I was at a fast food parking lot and I heard this loud noise coming from under the engine and when I pressed the button to stop the a/c system, the noise stopped so suspected the a/c compressor was shot. I then went to a mechanic across town and the mechanic installed a new compressor and desiccant bag behind the radiator as well as a receiver and dryer as well as recharge the system. After this, the air conditioner worked without any problems for 10-11 months.
After this, I was pulling out of another place and the a/c would only blow hot air. I then recycled the a/c system switches a few times to see if there was some problem. A few days later, I found that the a/c clutch relay had burn marks on it. I then went to an auto parts store and put a new relay in for the a/c clutch and the a/c worked for maybe 2 more days. Over the next few days, the a/c only worked intermittently and then not at all.
Then, I found the clutch was not engaging for some reason. I have spoke to two different mechanics one of which was a former ford mechanic which seems to has pretty good standing in the local area. He said that I would need a new power distribution box if it kept blowing relays. To get a new battery junction box is over $1500 because I was told it comes with all of the wiring harnesses and takes about 8 hours to install. As an aviation graduate with a background in electronics, some obvious questions started to float to my mind.
If the entire power box were bad, I think I would be having some codes and other major electrical problems. The power box in the hood has no less than 40 different functions. I am only having problems getting the a/c clutch to engage when I press the a/c button
Also, I do have forscan and a elm module can you provide some information on what I should check. I will be getting my new elm module Friday. I could use this to assist in troubleshooting.
I am almost certain though, the problem is electrical in nature because when I swapped the a/c clutch relay with the back-up lights relay
There is also a fuse for the a/c which was intact when I checked it.
Finally, I took apart the dash and found there is a control box behind the center plate of the dash for the hvac module.
I am wondering what the problem may be or if anyone can shed some light on if anyone else has had a similar experience.

and they didn't work indicating a blown relay. I recently tried a new relay and it too did blow.
Right now I have 119,500 miles.