Problem Adding Freon to APU

It has to be running

 

Maybe use R12 instead of Freon?

 

Is the compressor running (clutch engaged)?

 

If the clutch is not engaging and you have a static pressure of 15 psi, there are other problems. The drive hub on the front of the compressor should be spinning if the clutch is engaged.

The other thing is, these systems only hold 24 ounces of refrigerant. There is a very fine line between not enough and too much. I wouldn’t charge it from one of those cans—you need gauges. It really sounds like you should take it to an AC shop (not necessarily Thermo King).

 

Go to Harbor Freight and get a cheap set of gauges. Then go to NAPA and get a Mastercool can tap. This will allow you to use the individual cans of 134 that Walmart sells for $4.88. Do not buy a ####ty off brand tap from Autozone or Advance. Mastercool... Mastercool... Mastercool!

Hook up the gauges and completely empty the system out (very slowly so you don’t blow all the oil out). Connect the quick connects on the blue and red hoses and let the yellow hose dangle in a safe direction. Crack the blue knob open a tiny bit.

When it’s emptied out, close the blue knob (and make sure the red knob is closed too) install the can tap on a fresh can and screw it onto the yellow hose. Turn the knob on the can tap to pierce the top, then turn it back to open it. Use a small screwdriver to press the schrader valve on the manifold to purge the air out of the yellow hose.

Now hold the can upside down and open the blue valve a full turn to start charging refrigerant into the low side. When it won’t take anymore, turn the can right side up and go start the unit with the AC controls set to max cold. Leave the can right side up while the system sucks the can empty. When you dont feel anymore liquid in the can, close the blue knob, then slowly unscrew the can to release any remaining pressure.

Note... do NOT open the red knob for any reason. If you open the red knob with the system running, the can WILL explode in your hand.

Hook up a fresh can, pierce the top and purge the hose. Leave the can upright while charging until the system takes all of it. Close the blue knob.

Two 12 oz cans is a full charge. Depending on the ambient temperature, you should see 10 to 35 lbs on the low side and anywhere from 150 to 225 on the high side gauge.