A/C problem "fixed" on my 94. Very odd.

[kocke01]

So my A/C goes out on my 94. One day it just got warmer and warmer and then nothing. So, I figured low on refrigerant. Take a low side reading - 100 psi. Strange. Oh well it's a cheap guage. I buy some stuff to seal leaks. In the process of that the Compressor turns on. Cool (no pun intended). Pop a 12 oz can of 134a on, and it takes it all, but in the meantime the compressor has turned off. Weird. Pressure must have gone back down. Put in another can. Nothing. Damn thing doesn't even come on. So then I'm thinking maybe while I was filling it I did something to the electrical connector that's on the low side so I fiddle with that. Nothing. Ok maybe the connector on the compressor. Nope.
Now I'm thinking the refrigerant is coming out somewhere as fast as it's going in (all the while the psi is staying steady at 100 which is too high). Knowing I shouldn't, 1 more can (I know you're cringing now) while I listen for leaks (if it's coming out that fast when I turn off the engine I should hear something hissing).
Takes the can, no sounds. I'm stumped. Now it's war.
I turn on the truck and the A/C and grab my trusty hammer who I have engraved right on him "The persuader" (If this doesn't work I'm going to my other hammer I engraved "BFH" on). Anywho, I VERY lightly tap the compressor. Of course nothing, but it IS making me feel better. Now I go over to the low side and where the schrader valve goes in is a square fitting that goes down to a canister. I "tappa, tappa, tappa" the square fitting and the compressor comes on! Take a reading, and I'm at 45 psi. A bit high but in range. So, I let a some refrigerant out (the CORRECT way OF COURSE - it's not like I just pushed the little valve open, er, umm....). So, it's highly likely I have a slow leak there, but it also appears that there is some sort of blockage/or closed valve there that was causing the pressure reading to jump which I think made the compressor think everything was too high so it shut off.
So that's my story, anyone know the technical reason why "The persuader" once again lived up to it's name??

 

[RiverRat]

So you used the "persuader" on the a/c cycling switch? I liked the story

 

[sncwfo99]

might possibly be moisture in the system. only takes a drop to freeze up. there is a valve in the system too that can get plugged up but for the life of me I can't remember what it is called. I think if you have moisture you will have to replace the condenser (not positive) maybe someone else on here can chime in that know more than I do about it.

 

[RiverRat]

Some of the older design a/c systems used an expansion valve. In your truck you have a fixed orifice tube. If the a/c system was open for a while then it might have been contaminated with moisture. In that case the accumulator should be replaced.

 

[kocke01]

It sounds logical in the sense moisture may have gotton in due to the behavior, but for the life of me I don't know how. I never opened it up in the 4 months I've had it. What happened before that I don't know, but I did get 4 troublefree months. The pipe goes into the drier? (is that the same as an accumulator?), so if it's not doing its job, as I've used it moisture hasn't been removed. Not sure how to test that though, but if my "fix" doen't last I'll have to try that first. Fortunately the handle of "The Persuader" is exactly the size of a "C" cell mag light so I bought the mounts for that and he is permanantly mounted in the truck!

 

[Glacier991]

Interesting story. First of all, a low side pressure reading with the compressor not running doesn't tell you much. SO 100 PSI, on the low side, with the compressor not engaged is NOT high. (depending). The accumulator has a low pressure cutout switch on it. Assuming that your "persuasion" caused the compressor to cycle, it could have been that the switch was hung up and your vibrations knocked it free. As for freezing, without the compressor running that's not even a possibility, and running with low side pressure 45 out of the chute as soon as it does run and pull down the low side, t'aint gonna freeze. My best guess is a bad cutout switch, an overcharged system and something that jarred the switch loose. Glad you got it fixed. (If it is not just awaiting another seize up - I'd investigate and carry a spare cutout). Glad you got a gauge set, do a little bookwork and let it help you (don't mean to offend, but sounds like it might help you understand system pressures).

Chris

 

[kocke01]

Heh,
Appreciate it. If I could be offended then I shouldn't throw my ignorance out on the table like I did. I could definitely use the knowledge, and no I don't normally try to fix all my problems with a hammer, there was some odd logic there. I knew the compressor had come on and since adding refrigerant wasn't doing it I figured it was something physical that did it. Pressing on it, fiddling, etc. It's why I posted really for someone to come along and give me ideas on why it may have worked, not because I was proud of fixing something by banging on it. Of course I was trying to weave some entertainment value there. Now at least there will be a record of, "If you get to the point where you might want to grab a hammer to fix your A/C, try checking the cut-off switch"
It's also useful to know that a pressure reading is useless w/o the compressor running. It could have been much worse really. Because of that high reading I was convinced for a half an hour that that was the high pressure side. If my connector would have fit on the OTHER schrader valve I'd have tried to fill it from there and probably blown the can to bits right into my face. Thanks again. When it comes to stuff like this, I only know enough to be dangerous, so kids "Don't try this at home"

 

[kocke01]

Just a final update. It was in fact the A/C cut-off switch. I "fixed" it a few more times and then went to the parts dept.
It's about 30 dollars and takes all of about 10 sec to swap out. They were nice enough to use a schrader valve there so you can take the switch off w/o losing all of your refrigerent.
Thanks to all for taking the time to give feedback, especially Chris for being right