Any AC guys? Evaporator freezing up. Trying to fix before summer time.

[chevjerico]

This is for my 93. I'm not much of an AC guy, but a coworker told me that there is a pressure switch that may not be turning off the compressor that might cause this problem. Also a system that's undercharged could do the same. When I purchased the truck I noticed right away a larger then normal amount of water underneath after shut down. It does blow cold, but after driving for about 45 minutes it completely freezes up and stops blowing.

 

[RACE427]

Need to locate the low pressure switch, I would guess it is mounted on the accumulator. When you disconnect the wires, the compressor clutch will disconnect. The compressor should be cycling on and off on a correctly operating system. If not, then the evaporator core will ice up and stop absorbing heat from the pass compartment. Low pressure switch should be fairly inexpensive.

 

[chevjerico]

Hey thanks, I guess to R&R the switch you have to open the system. Is it possible to do quickly without losing too much refrigerant?

 

[RACE427]

Last one I did was on a 2006 Jeep Liberty CRD no loss of refrigerant, just was a simple take out and screw in. Switch was $ 16.00. Cheap enough to give it a try.

 

[RACE427]

No loss of any refrigerant !

 

[chevjerico]

Awesome....thanks!

 

[RVTRKN]

My 94 lost an evaporator due to LP switch failing in the closed position, icing up the evap and destroying it. Replacement part was cheap. It was pulling the entire dash out getting to the evap that was tedious.

 

[Bob4x4]

1st gens use a thermal expansion valve and receiver dryer and clutch cycling switch

 

[chevjerico]

1st gens use a thermal expansion valve and receiver dryer

So what does that mean?

 

[Bob4x4]

The refrigerant flow is controlled by the expansion valve,the compressor clutch is controlled by the clutch cycling switch.If this info doesn’t make sense to you you should probably refer the repair job to a pro with the necessary tools and skill set.The minimum tools required would be a gauge set and vacuum pump and appropriate thermometers

 

[RVTRKN]

Clutch cycling switch is the low pressure switch. And yes, if you don't know the fundamentals of refrigerant, regardless of its controls, have a competent tech do it. I belive the newer trucks (4th gen) use temperature to cycle the clutch. I just replaced my compressor, orifice (refrigerant control) and accumulator, but I have the knowledge, equipment and tools to do the job. I even added a crank case heater to keep liquid refrigerant from pooling, in the compressor that took out the OEM compressor.