Ehinfinity

Ok I.m driving home from work today and no more cold air. I notice that the green light that is on when the air cont. button is pressed is not on. So when i get home i check the air coolant lines and the pressure is at 135-145 PSI!!!! when it should be between 24-45 PSI. I bled the line and refilled. I changed the AC fuse that had blown and guess what, it works for a second and then pop, no more cold air. I check the pressure again and its up to 85 psi!!!. Any ideas on what it is before i head to the mechanic???? Im guessing bad compressor but...
thanks
Eric

Ehinfinity

bump bump

BlackFlag

Pure guesswork here, but in reading about a/c systems I believe somewhere there is a valve or something that adjusts pressure between high and low pressure sides. I think this valve can have problems sometimes, perhaps this is the problem.

Ehinfinity

Yea i read about that; however, i wasent sure if that could be the problem. It could blow the fuse due to a shut off point based on high pressure so, this could be it. How can i hot wire around it to check?
Eric

BlackFlag

Wish I knew the answer for you, but I have so little hands on experience with it that I wouldn't know where to begin. You may have already done so, but if not, do a google search with your problem description and see if you come up with any advise. Hopefully someone with more a/c knowledge here will pipe up soon and give you some more info. good luck!

Steveh29

Here's my two cents. When you're speaking of the air coolant lines, I'm assuming you're talking the air conditioning refrigerant lines. That said, the pressures can vary quite a bit depending on the make of the system, outside temps and humidity. Also, you HAVE to measure the pressures with the system RUNNING. If the compressor is not running, the pressure will be equal through the system because nothing is being compressed or sucked down.

The low side or suction side can run from 60 - 80 PSI with the high side roughly twice that when the system is running properly.

If your low side pressure is running very high, my first guess would be the expansion valve or metering device that regulates the refrigerant from the high to low side is stuck open. It's allowing compressed refrigerant to run unchecked through the evaporator and dump into the low side - raising low side pressure.

My second guess is there is an obstruction downstream from the service tap on the low side, allowing pressure to build on the low side preventing cooling and raising pressure on the low side.

You're also saying it's blowing the fuse for the compressor. This is interesting because my experience with locked up compressors has been the electric clutch will slip and make a heck of a noise, but not blow the fuse. I'd check the wiring diagram to see what exactly that fuse is protecting. There may be a shorted out pressure switch somewhere in the system that's the true cause of this problem.

Ehinfinity

Any 3rd gen guys have any idea, based on experience or vehicle manual that will say what the A.C. fuse in the fuse box under the hood is directly protecting?
Eric