1997 379 pete, a/c troubles

I had a 96 379, the A/C in it worked just fine, I don't think the year has anything to do with it. I suppose the evaporator could have so much crap covering the fins blocking air flow, thus not letting the orifice tube work as it should. Just a thought.

 

Is it just insufficiently cooled air, or are you having poor air flow from the vents?

 

My experience with Pete. a\c's is they work at least equal to or above average. The office tube deal was normally with R12 units changed to R134A. 1. make sure the heater is not circulating water. fix the heater control valve or install manual cut offs on engine. 2. Some Pete,s were bad to collect lent over the evaporator core. Take apart the inside and clean them out. Some models had a square grid cover over the fresh air inlet in front of the passenger door hinge. A lot can be wash out by using a tapered bar in one of the holes rounding enough for a 1/4 in. tube to go through it. Attach a 1/4 in. copper tube to a blow nozzle. Then wash it out with a water hose, air, water,air flushing it out the drain tube. Clean the condensor also(even if it looks good) detergent helps. A 1/4 Lb freon one way or the other can be 10 degrees in some 134 units. Make sure the air control doors-flaps are working properly.

 

Yeah, it'll take a bit of diagnosis to narrow it down... there are seven operating conditions of an AC system, with the first being normal operation... suffice to say, the remaining six lead to insufficient cooling. On these trucks, there is one additional test you wouldn't do on a typical passenger car, and that's the heater control valve... real simple... either close the valves to the heater cores, or, if you don't have valves, pinch off the lines with hose clamps (you can also use vice grips, but you want to be really careful with this, as they can tear into those coolant lines). If you have adequate AC at that point, then the heater control valve is the issue, and you'll normally end up having to replace it.
Other than that, there are many, many reasons why it could be.. could be insufficient refrigerant, too much refrigerant and/or PAG, blockage in the system, poor air flow through the condenser, contaminated refrigerant, faulty pressure switches, etc, etc. An AC system test would be the way to narrow it down.

 

Shouldnt have a water valve on that year of pete. Pull the passenger kick panel. Will be an actuator for inside/outside air in the lower right. There will be one that moves with the temp and then possibly another that runs the heater door. They are common to fail. Watch them and move the heater controls and verify they move full sweep