I’m currently working on a D6k cat dozer with an a/c voltage issue. I am getting no voltage at all to the compressor or pressure switches. However I am getting correct voltage to the ac compressor relay. I have supplied voltage to the compressor and noticed it to be working with correct voltage. Does anyone know where I could check from here?
Does the relay work? Are you getting power to pole 86 when you turn on the a/c? If you jumper poles 30 and 87 does the compressor turn on? Does pole 85 have ground?
I have switched the relays out with the revert fan relay and still have the same issue. I jumped pole 30 and 87 and found the compressor to kick on for the first time. 85 does have ground and 86 does have power
If everything you say is true then I would say you have two bad relays. Pole 86 is from the switch. Pole 87 is the load (compressor in this case) Pole 85 is ground and Pole 30 is fused power. Make sure that you have 24v relays.
Okay thank you!
The circuit to pull in the A/C relay comes as a result of the Machine ECM grounding Pin 12 of CONN J2 via wire C510-PL206. Terminal 85 of the relay has machine voltage suppiied to it when the key switch is ON. I would guess that in order to ground Pin 12 of CONN J2 it would depend on an input signal being received by the ECM from the thermostat at Pin 14 of CONN J1 on wire C509-PL211. Also in the same circuit with the thermostat are the A/C High & Low Pressure Switches. It's interesting that Wire C509-PL210 splits into two wires (PL211 & PL212) between CONN 12 and the ECM. One of those wires goes to Pin 14 of the ECM, the other goes to a grounded resistor located right next to the ECM. Not sure what the purpose of that resistor is. See below.