no power on ac wire to compressor

[NOPHO84K30]

Is there a fuse im missing on fuse block looked didnt see one. Or a spot for one had a aux heat ac spot but no connections inside it

 

[highdesertrange]

or a low pressure switch? highdesertranger

 

[NOPHO84K30]

Theres power at the switch on the dryer and the plug on the plug on the blacl box on the firewall...

 

[HotRodPC]

If I understand right what you're saying about power at the on the dryer, then I'd say it's what highdesertrange is suggesting. Could be the low pressure switch itself not letting power get past that point, or it is doing it's job, pressure actually is low and not allowing power past the switch. For testing purposes, you can actually jump that switch, then turn on your AC and see if that gives power to the AC clutch.

 

[Camo]

Start the truck and turn the a/c on. Disconnect the low pressure switch and do a monentary jumper to see if you get power to the compressor then. If so you either have a low pressure condition or a bad low pressure switch.

 

[NOPHO84K30]

Ah yes ok ill try it tonight thx guys

 

[highdesertrange]

you are on the right track now. highdesertranger

 

[NOPHO84K30]

Yes the jumper worked. The clutch engaged and has power thx for the knowledge ill let you know how the hard line issue gets fixed from my serpentine swap. If it will bolt up or have to make lines for it thx

 

[HotRodPC]

So now you know, either the low pressure switch is bad, or the most likely, your freon is low.

 

[practicalgiant2]

Hey yall, not sure if I'll get any answers, first time using forum stuff. Got an 87k30 I can't get power to the ac compressor. I've unplugged low pressure switch jumped it nothin, took dash controls apart cleaned vent switch, r134 pressure says its OK. But the two wires on top of compressor I cannot get power to . Any help appreciated

 

[75gmck25]

Power runs from the dash switch, to the thermostatic switch (low temp probe that goes into the evaporator), then through the discharge pressure cutout switch (which you apparently found) to the compressor.
- If the pressure is too low in the system, the low pressure switch turns it off. This switch is easy to jumper on to keep the compressor engaged, and you usually need to do that to get it to take the initial charge if you are filling it from one of the small cans.
- If the evaporator temp goes below about 35 degrees(where it would freeze), the thermostatic switch cycles it off.

Did you verify that you have power to the dash switch? I assume the blower fan runs on all speeds?