I have a 98 Ram 1500 and my A/C clutch wont engage. It worked fine last year but when I tried to turn it on this summer the compressor clutch would not engage.

I checked the power to the low pressure sensor and have power there. When I jump that plug I still have no power to the plug that supplies power to the compressor. I checked the relay (only one I know of is under the dash) and changed it out with a good one and no change.

Anybody got any ideas?

 

I think on your truck, high/low pressure switches just control the relay. Are you getting 12 volts across both those switches?

Could try swapping out the relay with another one, they are all pretty much the same in there.

 

he just said he swapped the relays....

you sure its charged up? the clutch wont engage if there isnt any pressure in the system.

also sometimes the compressors internals just blow up and may require a new compressor.

you may be able to run a couple wires straight from the battery to the compressor wiring connector on the compressor and run it straight to the battery to see if it will kick on.

 

I have not tried jumping straight from the battery yet because I was not getting power to the plug for the compressor. I figured if I was not getting power to that plug then my problem was there.

Is there by chance a fuse in the cab or somewhere else that might be a cause?

 

You are low on coolant, which means a leak. Most likely the evap core in the dash. Jump the the green plug on top of the accumulator. If the compressor starts it's low on coolant and you have a leak.

 

I have already done that, it is fine.

 

You've already done what?

 

Did you get a chance to ohm out the compressor coil? Un plug the compressor and see what reading you get for the coil. Also did you get a chance to download the FSM (factory service manual) from the FAQ section of the forum? All the specs and wiring diagrams are in there.

 

Don't know of any relays to swap under the dash. They are in PDC box under the hood, driverside. It won't engage if the clutch/coil air gap is to wide, also.