I have a 06 Expedition 5.4 with rear air. I purchased it with 55k on it a few months ago. They last two days I noticed that not only has the AC thumped when I start the car but the rear compressor makes a hissing noise. I put a can of R134a in it and both seem to have gone away.

My AC however does not seem to be as cold as one would expect however. Before my AC refill I was sitting at about 20PSI on a 95 degree day. I am now sitting at 45PSI. The can I put in was a stop leak ring conditioner with 11oz of R134a and 1.5 ounces of oil and stop leak.

Any suggestions?

 

There is no rear compressor 1 compressor runs both front & rear a/c, Take it to a pro have them evacuate it & recharge to proper capacity.