APU A/C Compressor Replacement?

@PE_Trans how many oz freon you have now inside? 55psi is ok. check both switches for continuity as he suggested. one of switches is located on drier. Second switch is located inside evaporator box(the box is located under bed). open the cover and you will see the switch.

 

here is he switch that is located in evaporator box

 

If you have the older style APU, the condenser fan on the back of the cab should come on at the same time as the compressor if you have it in AC mode. There is a programmable delay, after the engine starts, before the compressor will engage. I have mine set to 45 seconds.

It sounds like your binary switch is bad, setting the code right after the compressor attempts to engage.

 

That is a low pressure cutout switch which turns the compressor off when the pressure in the evaporator gets too low. The binary switch is located on the drier on the back of the cab.

 

Incidentally, if your local NAPA will let you look at their big book of AC parts, you can probably find a switch a lot cheaper than TK. Get a normally closed switch that opens below 15-28 lbs. And opens above 380 or so. There are two different switch port sizes, M-10 and the old R12 style 7/16-20... be sure to get the right one. R12 style has a flare and metric uses an o-ring and is squared off.

 

Checking the high pressure opening of the binary switch is a bit more complex. If there is continuity through the switch with some refrigerant in the system, then it may be opening at too low of a pressure once the compressor kicks on. It only has to open briefly for that code to set.

If you have gauges, you can jump the wires while you watch the high side. If the system runs normally, you’ve found the problem. Be ready to yank the jumper though if the pressure starts to climb rapidly toward 300.

 

As far as programming, it can be done through the original style control panel. If you only have a temp knob, you’re SOL.

My phone got wiped, so I no longer have a copy of the manual. I’ve emailed copies to a bunch of people on here though, so someone should have one.

 

I may have it.