A/C Problems.......Stumped

Those are the safe comp. cutoff sen. they cut power to comp. if press. gets to hi or low, the one on inside of heater box makes temp your air blows out of vent stay the temp at all times.

 

If this is a Peterbilt (I just saw your last post and I see it is a Pete) and from the way you are describing it it sounds like it is. There is no thermostat. There is a cycling switch slightly above and to the center of the cab above the ports where you connect the hoses to check pressures. This acts like a thermostat. Remove and inspect the orifice and replace it. They are cheap. Install a new accumulator. Flush the system out. Peterbilts have large tube condensers and you can flush them and blow them out. Make sure you blow and flush the lines and evaporator really good both ways. I have seen many Peterbilts have the rotary compressors put metal and plastic in the lines. Then vacuum it and make sure you put exactly 5.5 lbs of refrigerant in. I have seen Peterbilts that will not cool with less than the exact amount in the system. The sleeper has an expansion valve inside the box that has the fan in it.

 

I put in this post 5.5 of refrigerant. Some take less so put in what your label says.

 

Have you taken a look at the evaporator? I'm willing to bet that the fins are plugged with trash and dog hair.

 

My AC line would freeze up when AC filter was dirty.

 

Although you might have made some mistakes in your initial repair. The reason the system is freezing up is not enough freon. Always fill to capacity and when using cans It is easy to lose some freon. Even though you're not using the rear unit you still have to fill to capacity. I also recommend investing in a set of guages. It is important to know both low and high side pressures. At this point you do not need to replace the evaporator and condenser. And you don't need a sight-glass. If it didn't come with it, you don't need it. That's old-school. I deal with blown-up A/C's all the time.

 

"So the following weekend I changed out the tube again and saw it still had junk in the lines, was dirty but not as dirty as it was weekend before. Same thing, a couple days went by and lines freezing up again."

He said the lines still had crud in them and the orifice tube was plugged up again so, yes, the condenser and evaporator will have to be replaced.

And a sight glass would allow him to check the state of charge in the system if he blocks off the lines to the rear a/c, thereby modifying the capacity of the system. Much easier than calculating subcooling and superheat and more accurate than the old school method of charging with your hand on the outlet pipe.

 

Sorry dude, I disagree. I do this all day long. Why would he want to block off the lines to the rear A/C?!?! That's a hack job. He needs a set of guages. Period.