General Discussion

[joe1019]

I have a 420e that has no power to the a/c compressor. I have power at the switch and down to the fuze on the fuzebox at fuze 25. Anyone know where I might be losing the current to the compressor?

Thanks in advance.

[cbrer]

There's at least one pressure switch in all AC systems. Sometimes called a binary switch. It shuts off the compressor if

A: High side pressure goes to high, IE - really hot day (compressor would explode)

B: Low side goes too low, IE - refrigerant leak (compressor would never shut off and burn up)

See if you have power on one side of the switch. If you carefully jump the wire to the other side, the compressor should come on, if there are no other issues. Have you inspected all other wiring and components? There is also a capillary tube going into the evaporator to detect temperature and cycle off the compressor if it gets too cold and might freeze up. This is usually controlled by the operator with the temperature selector. If this is damaged, the thermostat side won't send a signal to turn on the compressor. And there could be more than one fuse. Sometimes one controls the evaporator fan inside, and another controls the condenser fans and compressor.

This would also be a very good time to blow out the condenser coils. Don't blow from an angle and bend fins. Does the evaporator have a fliter on it? Good time to check that too. Construction equipment typically clogs up pretty fast. Tell tale signs of leaks are wetness and oily dirt residue around fittings or damaged hoses.

Please post fix.

[joe1019]

I am guessing you are referring to the switch near the a/c compressor. Is that the one?

[cbrer]

It will be mounted on a fitting on a hose. Usually hi side

[joe1019]

That's what I thought and that switch has no power on either side. Must be a open or short somewhere. I have been digging and digging but so far no luck. 402e is not the friendliest thing to work on.

[cbrer]

A schematic will nail down the problem. I think most designs have power going through the thermostat. But if there's a separate switch to turn AC on and off, then there will be an additional relay that controls thermostat circuit. Good luck. Please post fix.