APU A/C Compressor Replacement?

you can manually engage a/c comp clutch. run apu in a/c mode, disconnect clutch wire from apu wire and supply +12v from truck battery.

 

If you're getting an ACS code, the compressor is shutting off from too high pressure. What is the high side gauge reading when the unit shuts off?

The binary switch on the dryer trips if there is less than 15 lbs of pressure (empty system) or more than... hell, can't remember but it's gonna be high, like 350-400. When that happens, the code sets and the unit shuts off. The usual cause is the condenser fan not coming on. Is it running?

If the fan comes on with good air flow and your high side pressure is... say 175-225, then it's probably a bad binary switch.

 

low pressure also will pop ACS code.

 

I would put 2 cans of freon in and if ACS is popping up I would disconnect binary switch and short two cavities with wire.

 

I guess it wasn't too clear from what I wrote above but yes. It is also likely the reason the compressor isn't coming on after shooting a partial can into an empty system.

You can check it with a continuity tester (or audible ohm meter) by unplugging it and connecting the probes to the switch. It should have continuity if there is above 15 lbs of static pressure in the system.

 

I don't recommend bypassing that switch or powering the compressor directly, even for a minute. If something goes wrong, the pressure can skyrocket in seconds and it will blow apart the weakest point. Hopefully only a hose, but sometimes the (very expensive) condenser.

 

there is a safety valve on drier. plus 24 oz of r134a cant make enough pressure to damage something. if system is overcharged then yes it's dangerous.

 

We'll have to agree to disagree. 24 oz will make plenty of pressure against a restriction or a condenser that's got poor air flow. Yes, the safety valve may pop, but then you'll be buying another, what? $60 drier if you got it at TK.

And a lot of times, on an old system, that safety valve isn't the weakest link.

That switch is easy to test with a meter.

 

@lilillill testing both switches with multimeter is the best way. @PE_Trans do you have 15 psi static pressure ? Static pressure is the pressure in the system when apu is off. Static pressure must be measured when apu was off more than 15 minutes.