AC gurus , need your brain for some picking
 

So.. A.C. recently refilled. Worked for few months. Cold. Consistently.

Yesterday , I did a 2 hour drive from 90F area to 115+ home town.

The A.C. worked the entire trip back. But once I got home. I let it sit for about an hour. And took it out again
The A.C. would turn on for about 2 minutes and shutoff. It would repeat that every 5 minutes
And when It goes through the cycle every time it turned on I would hear 1 short hiss coming from the glove box. Never noticed before but it could always been there but I just never paid attention.
All This was happening during freeway speed . During idle the ac stays on (a.c. compressor spins)

Is it shutting off on me because it's just too hot ? Super high pressure from heat soaking ?

Or is my Freon low but that doesn't explain the drastic change over the course of a few hours

Any advice or Input helps. Thank you

Air blows cold for about 2 minutes and then blows hot for 5 minutes then cold again for 2. On repeat

What refrigerant do you have in the car?

The hiss in the glovebox is normal when the compressor kicks off, I think it's the expansion valve equalizing.

It's kicking off because some input is telling the system to shut the compressor off. Either the pressure is going too high or low or the expansion valve is getting too cold and telling the compressor to shut off.

You'll need to figure out what is tripping the system to cut off first. Also for troubleshooting purposes you may want to try running the system at not-full-cold to see if it still cuts off.

Dale

It is running with R12 and I will test it just as you described thanks Dale!!

Did you go over the whole system and find any leaks or just throw a charge in it blindly? If it was low there is a leak.

Yea . I checked and found leaks at the Schrader valve and at the drier tank . Fixed those
And then proceed to charge it. Held pressure during testing

So tonight I took the car out for some diagnosing . At first. The car struggles to stay blowing cold air on multiple temp at speed 3 on recirculate for about 5~10minute . At the same time I can hear the expansion valve hissing every 5~15 Seconds. Then all of a sudden. The a.c. stays blowing cold for the next 20 minutes with out missing a beat. Then I parked it idling with a.c. on speed 2. For about 10 minutes the fan is working as it should . High and low all working. Then back on the road I turn it to speed 4 and that's when the ac stops blowing cold air for about 5 minutes. Nothing just didn't turn on at all. Then I change the air direction from straight forward to forward and feet and I hear the compressor turn on along with one hissing sound from the expansion valve after that the AC pretty much stayed on until about 10 minutes later when I park the car and shut it off

Ambient temp was 105f

You need to put dye in the system to check for more leaks.

The FSM has a number of tests to perform to diagnose the problem; I was looking through it just yesterday. GENERALLY speaking what you have sounds like a classic high pressure compressor shutdown, which as others have noted can be caused by several things. Given that you seem to be able to affect the phenomena by various switch/temp settings, it may not be totally out of the question you have an issue with the electrical controls on the dash.
A qualified a/c shop should be able to sort out your issues quickly. I know several years ago I had an Audi that was driving me bat-Shiite crazy and the shop I took it to figured it out after a couple of hours (it was an issue with the control panel!).

I busted out my FSM too before I went to bed. I'll go through that more thoroughly next time

I hope it's not my electronic cause thats pita. So if it a high pressure shutoff either it's too high or too low

But only after heat soaking . That is when it starts to go bonkers .

This shit will drive a man to drink...hang in there!

I'm taking it to get the Freon level checked. Just now the compressor would not kick on at all. Driving or idling .. tried for about 20 minutes lol

do you have a set of manifold gauges to read the high and low side pressures?

unfortunately i dont . is it somthing i can go rent a set at my local auto parts store ?

Harbor Freight sells a 134a set for $59.99 less the 20% coupon so about $50 net - the hoses have screw connectors that attach to the special 134a connector, but the connectors on the hoses are the same size as the R12 fittings AFAIK so the 134a kit shoud work for R12 also. So for probably less than the cost of having it checked you can have a gauge set.

I recently bought one of these kits to check and top off my FD - after 22 years it was about 5oz low - the HF gauge set worked great and is good quality... great quality for the price actually. Even includes a nice plastic carry case.

Try spraying the condensor with cold water to see if it kicks on the compressor. I noticed mine kicked on when i did this in fan speed 4. When it was jsut sitting there idling it would not kick on.

And yes u should be able 2 rent the gauges from local parts store.

You can also temporarily jump the compressor with a 12v positive power lead and see if it kicks on, and see if you have a lot of bubbles in your sight glass.
Don't run it this way for more than maybe 30 seconds or so...

i went and picked one up today. i didnt have the 20% coupon but a older gentlemen was kind enough to give me his :lol: thanks for the heads up. i have a 93 MR2 thats a R12 as well and i can use this on both of my car :icon_tup:

i will give this a try tomorrow. thanks

i tried and the compressor dose in fact turn. hmmm

So the HF gauge set worked great for hooking up on the lowside .but the high side fitting don't fit



Anywho. I hook it up to the lowerside with the engine off cause the compressor won't turn on at all so I saw no point. Once I hooked it up and open up the nozzle it showed 0psi on the lowside

Just in case I was doing it wrong I unhooked it and took a screwdriver and pressed down on the Schrader valve . There was nothing coming out aswell. So in conclusion my system is empty and there is a fat leak somewhere . Am I right ? Last time I refilled it I had fix 2 major leak. 1 was a filthy Schrader valve and the other was a leaky dryer the dryer had rotted O-rings so I replaced it with R12 compatible ones. After that I had pressure test the system and it held pressure but this was an ambient temperature of maybe 80 during the winter and now it's about 110f on the daily somhow another leak showed up ?

still scratching my head on this one

Unusual finding a place that has R-12 that didn't cost you a fortune to charge, just checking it still has R-12, not been converted to 134?

It's r12.. I had it refilled and fixed of leaks. In March. My ac guy doesn't charge me much. And plus I have about 6 cans of 14oz DuPont R12 as back up In case I'm in a jam

Good you have R-12, I've got 2 30lb containers and maybe 15 small cans, but if there's no pressure in the system, it had to go somewhere, but if cold, or colder at idle, then drops as rpm's increase, symptom of low charge. Seems as though you know how to locate a leak, so good luck.

So. I have found the leak. And it's a big one. It's behind the compressor at the high pressure side fitting . Suspect the o ring has failed

When I charged the system it wouldn't hold any pressure and I can clearly hear the hiss from leaking ,Pin pointed to that fitting. So now that I know where it is

My only question is is it necessary to remove the power steering pump or I can just do it with the elbow removed