Hi,
It should be in the power distribution box under the hood.
Have you checked the amount of charge in the system, there is a low charge switch that won't let the compressor engage if it's low, it's a round thing that looks like an oil pressure sending switch.
Rich

 

Thanks Rich. Well, I think its charged. I bought a freon cannister today from O'Reilly's that had a gauge on it as well. It was out, but I charged it until it was right on the "green" which it said not to go any further. After doing that, it doesn't seem like the compressor clutch is engaging at all when the air is turned on, and it still doesn't blow cold.

I think I either have a bad compressor or there is something electronically keeping it from engaging.

I just bought the truck last fall for a work truck, so don't know much about its history.

Appreciate your help. Any other thoughts?
David

 

The low pressure/cycling switch Richard is referring to should be mounted on the Accumulator. Big aluminum canister hanging off the Evaporator on the passenger side. It should be a two prong switch. You can pull the connector and jump the terminals and the compressor will kick on if this is the problem. If it does kick in then the charge is still too low. If the system is empty or nearly so it may take more than one can to bring pressure up enough to keep the LP switch happy. Be careful, when there is no/low charge you have little or no oil (if there IS any) cycling through the compressor.

If the system wasn't cooling and cycling at all before you started then it was probably empty and you have a leak. Look for signs of oil around hoses, connections, compressor, etc. If the system leaked it probably took most of the oil with it and adding a charge without replacing the oil is likely to destroy the system. Not to mention it probably has air in it. Bad combination.

 

The problem with the gauge & can you bought from the store is that its only reading the low pressure side of the A/C, and you need to measure the high pressure to know if the system is working.

There should be both a low pressure and a high pressure cutoff switch in the system. If the system is contaminated (and something maybe plugged), the high pressure cutoff may prevent the system from coming on. On the other hand, the low pressure cutoff will disengage the compressor if there isn't enough R134 in the system.

I think most places charge too much for a basic A/C service, since they just let the machine do everything to evacuate and recharge, but you might have to pay for the service just to get started on troubleshooting. If basic evacuation and recharge does not work, then you have to hope they can narrow down the problem to something you can fix (relay, temp sensor, orifice tube, etc.). If you have to open the system you will want to replace the receiver/dryer, and maybe even have it flushed.

Bruce

 

The problem with charging from the low side only with one of these cheap kits is that it takes quite a while for the freon to migrate through the system. If the system is very low, you'll temporarily read high on the gauge due to the orifice tube slowing down the passage of the freon. Having the compressor running when charging is mandatory. As noted above, jumper across the pressure switches temporarily to get the compressor to run.

 

might have to vac system down first,, so that it can take enough freon to cycle(about 5 cans when vacked down)
going to a shop will cost around$55.00-75.00....
if you can find a friend with guages....bring beer...
or if you want to learn... cheep guages (harbor frieght)$35.00 ...vac..$20.00 ..+ freon..+book to learn...the guages tell all... almost...
do a couple..and your friends will pay you to fix a/c...