Hi there all! Couple of brief questions but some background first. I am very mechanically inclined however I have done very little AC work, mainly because Ive always had the money to let someone else mess with it. Unfortunately that is no longer the case so I need to do everything I can myself to save some green. I have searched the forum and google extensively and have yet to come across the right combination of search terms or what I'm looking for, not saying its not out there I just cant find it and would greatly appreciate some help if possible. I have a 2001 ram with a 5.9 pretty much stock motor, the problem I'm having is that air is no longer blowing cold. I have recharged the a/c in the truck before with absolutely no issues. However when I went to charge it this time the low side guage keeps swinging from 10lbs to approx 55lbs. I dont remember it doing this before and its like it wont take the freon. I have owned the truck for 3 years now and the compressor has always cycled on and off through out use. Again any suggestions as to what the problem might be , or tell me I'm doing it all wrong and show me the way, will be met with grattitude and sincerity. Thanks again all. -Mark

 

i'm not an ac expert, but usually the compressor cycling is due to either too low, or too high of pressure.

with a gauge on the low side port, you'll notice that when the compressor is running, you should have about 25-35 psi. when the compressor is off, whether because its cycling, or because you turn it off, then the pressure goes much higher. i think this is because the system equalizes. so - you may have to jumper your compressor switch to keep it running. i'm not sure which switch you jumper, but maybe a search will show it.

the compressor will have to be running in order to create a low pressure zone for the refrigerant to expand into. and i don't think you're supposed to dump it in upside down as a liquid (i did it once, but found out that's a no no)

 

Your pressure is too low. Those refill cans only work when it is running and can pull some in. If it is too low it won't run to keep it from damaging itself so you can't add much. Sometimes with a refill can you just have to wait it may take a while.

You say it bounces up to 55 this is probably when the systems shuts off. If you don't want to jump the compressor go out in the morning when the truck is cold and refill it then. Dont run the truck either but submerge the refrigerant can in hot water to build pressure in the can so it can force it into the system. With it off the pressure will be the same on low and high sides. Refill it until the pressure is about the same as the air temperature.

 

i just had the same problem with my truck. when the compressor kicked on, i pulled the trigger on the refill can, when it kicked of i let go. so on and so forth until the compressor stayed on and then it would take a full charge. if you just hold the trigger the system will act as though it is full. especially if it is hott outside.

 

Get a can or two of refigerant and connect it to the low side. Pull the connector on top of the accumulator. Put a paper clip (or any wire) in the connector to jumper the connection. This will keep the clutch engaged and recharge the system. You probably have a leak that is causing your pressure to be too low.

 

Pulled the sensor off accumulator and jumped it, compressor kicked on immediately and didnt shut off/cycle. Blowing ice cold now, Thanks again guys, driving home in 100 degree heat in west central florida was not pleasant without AC.

 

I wouldn't run it long like that. There is a reason that sensor kicks the system off when pressure gets low. Grab a couple cans of R134, with the gauge, follow the directions, and recharge the system.

 

The guy I bought my truck from, said he had AC problems (cycling it on/off). He took it to a shop to have it fixed, and the only thing that was wrong with it was the relay.

Looking at the relay... they are much smaller than the "bosch" style ones I am used to working with. Maybe you could get lucky and try a $10 relay.

Good luck,
Cartman

 

a clogged orifice tube can cause rapid cycling also as the freon will not flow through like it is supposed to.

 

sorry i didnt state that when i jumped the sensor on the accumulator i also refilled and charged the system at that time. Jumping that sensor cut down the time dramatically that it took to recharge/refill the system as opposed to waiting until the clutch on the compressor engaged. The clutch no longer cycles on and off and operates as it should. Thanks again to everyone who helped. On a side note if anyone has to replace their distributor cap, i would highly recommend using a 9/32 nut driver as opposed to the #1 or #2 phillips screwdriver. did the plugs, wires, belt, oil, coolant and hoses today. would have saved myself about 30-45 minutes if i had grabbed the nut driver first. maybe this will help save someone some time and skin off their knuckles. Had a little bit of a rough idle after the old girl warmed up, so i did an overhaul on the ignition electrics and now she purrs like a kitten and throttle response is notably faster. Had a lot of corrosion under the cap at the contacts and the rotor was worn almost 1/8" according to my calipers. Thanks again to all who contribute here, I am very grateful that there is a source of knowledge such as this that we can tap into, and will do my best to return the favor when possible.