Looking for some ideas on why my AC clutch is not turning on. I do not have any AC gauges but if I unplug the compressor and put a meter on the 2 harness pins, I do not see any voltage when truck is running and AC on. I really don't know much about AC but I am thinking the problem may possibly be the low pressure switch or possibly low on freon. How can I check if I am low on freon without gauges? Where exactly is the low pressure switch located on my truck and if I jump the switch and the clutch kicks on, does that tell me that the problem can only be the low pressure switch or low on freon? I picked this truck up for a $1000.00. I'm just trying to work through a few of the gremlins.Thanks

 

you can buy a can of R134 that has a cheap hose and low pressure gauge as part of the can........ or buy a hose / gauge combo that you can install replacement cans onto as needed.. SOMEHOW you need to put a gauge on the low pressure side and see what pressure you have with the system NOT RUNNING... that will tell us how much gas is in the system.......... a "GENERAL" rule is the low and hi side will stabilize about 90- 100 psi on BOTH sided sides when unit is off, then after starting the compressor the LOW drops to 30-40 and the high side goes up to 200 PSI.... but you need at LEAST one gauge to start the test.

 

Thanks Steve. Where would I check the low side from? I see the port right in front of the battery. There is a switch right next to it but I think that is the high side. Like I said, sorry for being ignorant but I'm a fast learner. Thanks again

 

yes, on my 2002 I think the LOW side fitting is between the battery and radiator. Your looking for a plastic cap about 3/4 inch diameter that screws off easily and leaves a snap on fitting that the R134 will clip onto.. will post a photo

 

you screw off one of the two plastic fitting shown below and you will see the steel snap fitting below it... it will have a check valve inside it so the gas does not leak out... the hose you buy will clip onto this... The HI and LOW are different sizes. the LOW hose will not clip onto the HI fitting.

 

If you have ever used a "quick disconnect" fitting on an air compressor...... that's how these fittings and hoses connect together.

 

the hose/ gauge / bottle look something like this... try to get one where the hose and gauge come off and can be reused... check NAPA, AutoZone, etc

 

I don't have the plastic cap on my fitting. Its an open port but I can check that one. Thanks for the info, I'll let ya know how it goes.

 

sometimes the caps fall off...... not a big deal... get another or put a piece of duct tape around the opening after your done to keep dirt and dust out of the valve.

make sure the inside of the fitting is clean - or blow into it to get any dust out BEFORE you connect the gas hose (R134).

 

The fitting between the radiator and the battery is the HIGH side port. LEAVE IT ALONE!!!

See HVAC FAQs, link is in my signature.

 

Thanks Project - Good info. I'll probably do a quick jumper on the low pressure switch to see if I get 12V at the compressor, then take it in to have it checked for low freon.

 

Your low pressure port is back toward the firewall on the same side. You have to get your head down low and look under the wire bundle near firewall.

 

Well I pulled the plug on the low pressure switch and the plug on the compressor. I put a meter on the compressor side and started the truck and turned on the AC max. I then jumped the low pressure switch and read 14.4V on the compressor side. I then plugged the pressure switch back in, turn AC on and off and saw my voltage at the compressor side follow the on off exercise (0V off, 14.4V on). I'm thinking I originally had a bad connection at the low pressure switch. I plugged the compressor back in and turned AC on and the clutch did not engage. The clutch will spin by hand. Do I have a bad compressor? I do not have an extra plug for the compressor to directly jump the compressor to the battery. I may rig something just to test but knowing that 14V is present at compressor when AC is on and the clutch fails to engage, I'm thinking the direct jump to compressor will only show that the compressor still will not turn on. Does this make sense?

 

Did you check clutch gap?

 

I did not. What is the acceptable range? I remember reading about the gap but do not recall what it should be. There are shims behind the clutch plate if adjustment is needed? Right? Can that be done if needed while compressor is still installed?