07 MCS 66k.

Recharged the system, AC blew nice and cold while driving main roads. After about a 40 minute highway drive, I noticed the AC getting warmer and warmer, to eventually not being cold at all. Weird thing is, is when I come to a stop light or really low speed, it gets cold again.

Any ideas on where to start?

 

It kind of sounds like one of the pressure switches is shutting down the system. At idle the pressures allow the system to function.

 

Wild guess here; but it sounds like you over charged the system..

 

It did this same thing before, but not as cold. Completely drained the system and then recharged to appropriate level.

Where are the pressure switches located?

 

I would recommend going to Harbor Freight and picking up a set of gauges they will tell you all you need to know. It sounds like you overfilled the system and will need to re-do it. You can do a fair amount of damage by overfilling. The gauges will take out a lot of the guess work. I very much doubt you have a problem with the pressure switches, given that it sounds like they are doing their job. See link below for the gauge kit.

http://www.harborfreight.com/a-c-man...set-92649.html

 

Thanks for the reply.

I have a set of gauges. I put in a little over a pound of refrigerant, that's what I've seen to be the correct amount. 1.08 to be exact.

 

are your gauges any good? it sounds exactly like a overfill problem maybe get another set to see if something is wrong with your set.. and was the system empty before you put the pound in? did u use a vacuum pump to remove all refrigerant? did you weigh what you pulled out?

 

Too much oil from adding the oil+r134a cans can cause a similar issue...many cans have oil plus gas...if you don't shake the can as you add it, or keep adding cans over a couple years to make up for a leak, the oil volumes keeps getting higher....