Engine/Transmission (1994 - 1998) AC compressor not kicking on=electrical issue, please help!

[Bobcat698]

Took the truck in to a repair shop today. They verified that there was enough R134 in the truck. .

They did some testing and found that the following wasn't getting power, somewhere between the cab and the relay box there is a problem:

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Please HELP! I need AC very soon!



Thanks in advance!

 

[DavidC]

If in fact you have no power at the line side of that fuse you would probably have more things out than just AC. I have a 99 service manual and the contact on the start switch feeds 4 fuses, so if it was the ignition switch there would be 4 items that do not work. You need to find the diagram that feeds that fuse and see if it indeed feeds others. The next scenario if no power on the line side of the fuse is a wiring problem at the fuse location that feeds that fuse ie. broken wire. I would get ahold of a meter and put the ignition switch in the run position and verify that there is not voltage on that fuse. Maybe they checked the wrong side and the fuse is blown. Stranger things have happened.



Dave

 

[Cummins360]

Check The Grounds too, and the relay its self.

 

[Berrigan]

First thing I would do is unplug the low pressure switch and jumper the 2 wires together in the connector cavity. If you get the compressor to spin then change out the switch. Its on the passenger side of the truck near the fire wall, on the low pressure side of the refrigerant piping. Bill

 

[Bobcat698]

First thing I would do is unplug the low pressure switch and jumper the 2 wires together in the connector cavity. If you get the compressor to spin then change out the switch. Its on the passenger side of the truck near the fire wall, on the low pressure side of the refrigerant piping. Bill

Thanks for the advice, but I forgot to mention that i tried this on the low presure & the high pressure switch.



The fuse panel has power, but the relay does not. .

 

[Berrigan]

Did you try swapping relays. I think the ac relay is the same as a lot of others in the pdc. I tried to read the schematic you posted but the print is too small to read. Bill

 

[DavidC]

So I take it we are still talking about the relay coil supposedly not having power. How was it measured?. If you have power from one side of the coil to ground then you are missing the normal ground for the coil which could lead to the switch in the cab or elsewhere. The way the fuse is fed I would bet it is on the ground side of the relay and you actually have power on one side of the coil.



Dave

 

[DavidC]

Check that ground wire on the right center support that goes to your dash switches.



Dave