2nd Gen Non-Engine/Transmission AC System FROZEN! why?

[Woodenhead]

Was cruisin to Spokane to go to the Rodeo yesterday and eventually notice I had no air/heat coming into the cab through the vents. If I put the selector on recirculate you could hear the fan howling away, if it was on outside air the fan could barely move any air.



When I went to fuel up I noticed every part of my AC system (high and low pressure lines) had about 1/8" to 1/4" of solid white frost on it .



I had my stainless grill inserts in and removed them just in case they had anything to do with it. Then drove for a bit (now in town), it didn't take long to thaw everything out and get some heat again.





Here's my take on it:

It was really foggy (ice fog) and freezing outside. I had the defrost on. I wonder if the high moisture freezing air froze up my evaporator, blocking the air flow into the cab. The AC probably kept cranking away with the defrost on but the refrigerant wouldn't evaporate or warm up so eventually it froze up the whole system.



What do you think?



I'm no AC expert so I'm hoping someone can shed some light on this one for me.



Thanks in advance



Mike

 

[B.G. Smith]

Originally posted by Woodenhead



Here's my take on it:

It was really foggy (ice fog) and freezing outside. I had the defrost on. I wonder if the high moisture freezing air froze up my evaporator, blocking the air flow into the cab. The AC probably kept cranking away with the defrost on but the refrigerant wouldn't evaporate or warm up so eventually it froze up the whole system.



What do you think?



I'm no AC expert so I'm hoping someone can shed some light on this one for me.



Thanks in advance



Mike [/B]

I think you nailed it, I believe the ambient temp. sensor is bypassed when the defrost is on so the unit will run even in cold weather, make sure the compressor is cycling on and off. It should cycle off when the pressure gets to about 10 or 15 pounds. bg

 

[Woodenhead]

Again

Was cruisin home the other day and it did it again. It was raining out and I was on the highway. Same deal, no outside air and all AC components frozen. I turned the defrost off and kept driving and it thawed out just fine.



What could be causing this? Anyone else having this problem?



Mike

 

[B.G. Smith]

The most likely cause would be that you are a little low on refrigerant. Not to be alarmed, could be just a small leak at the compressor seal, not that unusual duting cold months when AC is inactive. bg

 

[Woodenhead]

BG

Thanks for the info.

My compressor is about 1. 5yrs old, had a new dryer and orifice installed at the same time. My compressor runs daily with the defrost. Maybe it's time to get a shop to check pressures and for leaks. I thought AC systems froze when they had too much refrigerant (learn something every day).



Is it possible that there's a pressure switch screwed up somehow causing this?



Mike

 

[B.G. Smith]

The clutch cycling switch controlls the cycling when the system is on, yes, it could be defective, it is screwed into the side of the accumulator and can be replaced without discharging the system. Check and make sure it is tight, it is mounted on a schrader type fitting. The switch should open at 25# and close at 43# or thereabout. bg

 

[DJW]

I read somewhere that the air conditioner should be run periodically to keep the seals etc lubricated and to prevent drying out. Scrum Down.

 

[Gary - K7GLD]

Low refrigerent and clogged air filters/evaporator coils are the 2 leading causes of AC's icing up...