I need a little advice... when the windows fog up i turn on the defrost and nothing happens to the fog, the air is hot and it blows good, there is no smell of antifreeze and i put a pressure tester on the radiator with no drop in pressure, the a/c compressor kicks on but the windows continue to stay fogged up. i checked the pressures on the low/high side, the low side will go up to about 40psi then the compressor will kick on and it goes down to 20psi then the compressor kicks off, the high side wont get above 50psi i know thats low so i tried to charge the system but it woulnt take any freon. the outside temperature was around 50 and the compressor cycles on and off like its not charged. i dont know if the orifice tube is clogged giving me a low reading on the high side or what, i am guessing the a/c not working properly is the reason for the defrost issue. i would appreciate any help on this.. thanks

 

Yep I think you are on the right track about the lack of a/c being a possible issue with the fogging. Not sure why it won't take a charge though. I assume you are trying to add the refrigerant through the low side port with the system running?

Another couple places to look regarding the fogging:
- make sure your recirc door is opening to let fresh air in when on defrost.
- make sure your evaporator drain isn't blocked and keeping a puddle of water inside your evaporator housing.

 

the one door that i can see is moving when i cut any selection on is the door that is right behind the glove box, i didnt think it was suppose to move no matter what the selection is but it closes to where you cant see the fan inside when you turn the **** to anything but off. the drain is intresting though i havnet checked that, do you know where it would be located? do you know if the orifice tube would be another reason that the high side would have a low reading or would that make the low side have a high reading?

 

The recirc door is the one on the far right of the box. It should be closed on max a/c, to take air in from the cab. On all the other modes it should be open to take air in from outside the truck.

The drain is a small tube that sticks through the firewall to drain moisture from the bottom of the evap housing, right under the evaporator. You can see it (sort of) from under the hood, sticking through the firewall directly under the accumulator. Small black tube, maybe 3/4" diameter, protruding only like 1/2". You can maybe puff a bit of compressed air into it from under the hood to check for blockage.

If the orifice tube is restricted it would tend to make the high side pressure higher, and the low side lower. If the orifice tube was missing, it would tend to make both the pressures more equal and low like you are seeing, but that isn't a normal condition unless someone has recently had the system apart. Your description of the pressures and cycling makes me think that the charge is low. Without you being able to add refrigerant, the next best diagnosis would be for a shop to reclaim the system and measure how much was in it.

 

thanks for the advice i am going to check that drain and pull the freon out so i can recharge it. thanks again.

 

You're welcome. Hope it goes well for you.