Air Conditioning

[JungleJim]

My '95 Z71's A/C is freezing up...........literally. I have noticed in the past that at time it would quit blowing from the vents while you could hear the blowing running. Yesterday,I opened the hood to find about a 1/4" of "frost" covering all lines into and out of the evaporator case, the evap case "sweating" inside the truck and I figure the decrease in air is from the "frost" build up on the evap itself.

 

Usually a little freezing up is caused by moisture in the system.........however, this system appears to have never been opened.

 

I'm wondering.......could I have a "runaway" high press switch?

[raventai]

there is a temp controlled orifice (sorry forgot the name) at the begening of the evaporator is job it to keep the evap above freezing ~35*

 

 

that sounds like your culprit

[95 Silverado]

the switch on your accumalator (low pressure switch) is most likely the problem, the orifice tube regulates the flow of freon into the evaporator but it can not shut it off, when the evaporator temp reaches its low limit the low pressure switch is supposed to open and turn off the compressor until the evaporator warms up again, if its staying closed the evaporator will get too cold and freeze up.

[Carrierdealer]

The temp control orfice is called a thermstatic expantion valve.

It job is to mainatin 10 degrees superheat across the evaporator coil.

 

If it is bad or blocked the suction pressure will drop to low causing to cold of an evaporator causing it to freeze up.

The air conditioning should not put out cold air at all since the evaporator is being starved.

 

The low pressure switch should be cutting this off also.

So I agree with the suggestion to check the low pressure switch.