Automotive Air Conditioning Information Forum

My trucks ac has never worked since I got it a few years ago. I wanted to try an a/c recharge kit because I'm not spending anymore money on it with over 350k miles on it, also I'm getting a new vehicle soon. i know what you guys are going to say about not having the proper equipment and trying to recharge but I don't care if the system gets more damaged because it will never be fixed. That being said when I started (max ac and blowers waited for 5 min) the pressure on the low side was 0. I started adding R-134a to the low side. Evutually the clutch started to engage for 3 sec then cut off and it would repeat that cycle. I didn't know to much about it so I wanted to get help. I came back to it the next day after work and the static pressure was alittle over 100 but when the clutch would engage it would drop to around 10 psi and repeat the cycle every three sec. I feel like it is just low on refrigerant but I don't want to raise the pressure too high. Please help me with possible complications or a rough diagnostic. I know I should have manifold gauges and should have vacuumed the system for 30 min before starting.

Thank you for you time.

It's undercharged. Look for a sticker or look up in the service manual for the amount of refrigerant required. One can is not going to be enough.

Finding the pressure at zero usually means there's a serious leak.

Doesn't matter how much you put in it-- it all will come out via your serious leak.....o psi means you are completely flat-- would you just add air to a o psi tire and run with that? Expect to find and fix your leak if you want it to cool.

but the static pressure has stayed the same for a couple hours now. I guess I should find the leak before wasting a lot of money on refrigerant

It is refrigerant (a condensible) not air (compressible)-- you can have 2 ounces or 2 lbs or 20 lbs and static pressure will be the same! That is why we say pressure means very little until you weigh out or in the refrigerant amount....

Understanding that your truck is on its way to the salvage yard, and that proper AC repairs aren't going to happen on its way...and that any damage that doesn't include injury isn't a big deal...

Look your truck up inline, find the amount of refrigerant charge it takes. My '01 Silverado takes 2lbs, for example. I would add as close to that amount as you can, dunking the emptying cans in a bucket of hot water to boil as much out as possible. Watch for the low side pressure to drop down towards 35-ish, if it starts climbing back up stop adding.

Should get you at least cooler air out the vents, and then check the low side pressure in a week so see if/how fast it's losing. If it's holding for a couple of days, it might not have a leak but might have been discharged by the previous owner.

You can also find refrigerants with dye in it as well, that way you can take a uv light to see where its leaking from but if your not planning on fixing it (if it is leaking) I would skip the dye.