A/C not cooling

Low pressure Schrader has definitely got a slow leak. Testing the HP Schaefer. I am going to try to pick up a tool for changing the Schrader valve stem without losing pressure in the system. Anything I should be aware of for that? At 25 PSI, has the system already been compromised and do I need to vacuum anyway? If there are other leaks they are so small that I can't see them. How beneficial (or detrimental) is the r154a with leak stop?

Don't use leak sealer unless you want to start changing other parts, it has a nasty habit of causing failures in valving and compressors. I would probably opt to pull a vacuum but it's not strictly needed.

Thanks for the input. Had to go for a long drive today.. some of it in traffic and 80-85F in the sun. I had put a finger of a nitrile glove over the high and low p valves in case that was the problem... The A/C worked great all day! I plan to change the Schrader cores tomorrow and then pull a vacuum and then charge the system. I was under the impression that 200 PSI on the high side (45 on the low) was a target to shoot for with the compressor running and the car idling.. did I read that correctly?

Pressures all depend on the system and temperatures. For the temps you posted the pressures at idle look okay, It's possible that just the schrader leak is the issue, those can act strange at times and actually increase how much they leak as the pressure on the internal seal drops and the seal surfaces "relax".

Yes. Came out this morning and the glove was sucked down on the LP Schrader. Pressures were 20 and 25 so I imagine that I have a leak somewhere close as well. Changed the Schrader cores and the o-rings on the fittings on the firewall. (I was able to see a little better with the UV light as I started while it was still dark). It seemed like a possibility that they were leaking a little. Pulling a vacuum now and will recharge and let you know what I find. If this doesn't work, I think I will need a sniffer. Thanks for hanging in there with me!

If it was drawn in it's leaking, but there is also a leak somewhere else if the numbers dropped like that.

Agreed. I don't have the car today, but am going to check the pressures when it gets back. I think that I will have to get ahold of a sniffer.

Well, that was not successful. The car was driven for one hour this morning.. A/C worked okay. Coming back in the evening, A/C not working. I tested the A/C when the car got back... engine still warm and idling testing 85LP and 85HP, 10LP and 100HP when I turn on the A/C... clearly still losing refrigerant. I will see if I can get a sniffer and go from there. Thanks for your patient help.

You will find it.

Hey Steve. Finally got some more time to work on this. Took the car to a mechanic and paid him to use his refrigerant sniffer to try to find the leak, but no joy. He suggested that I replace the out line from the compressor to the condenser as he often sees them go. Once that was replaced, A/C is nice and cold, but still has periods, while driving when A/C basically quits. I cannot hear the click but I am thinking the compressor must kick off. Layer on the same drive, the A/C will work again. I have been waiting to see if I still have a leak, but the pressure seems to be holding.
Do you think I might have a sensor issue?

It's possible because of the number of times it has leaked down. When it came back on after shutting down, did the air smell any different? Like the musty smell that you can get from ice melting? Was it humid at the time it shut off?

It is humid. Not musty.
Thanks for your help!

Okay, humid could have made the core freeze up, the system will then shut down until the ice has a chance to melt away from the sensor. That could take a bit. About the only way to know for sure would be to connect up to the sensors and watch what they are doing.

Right. Can I bypass that sensor to test if it is the problem?

I can check to see if the evaporator is actually freezing?

The connector for the sensor is outside the case above the blower motor. With it unplugged you can test for the resistance using the table. If it isn't correct then it gets replaced. That could be tricky as the sensor is actually set on the evaporator core. The book tells you to remove the core to replace it but if you could reach in there through any opening and get to the core you might be able to just stick the new one in there and connect it up. I know of one person who reached in through the cabin filter opening.
To check if it's freezing up would involve seeing the intake side of the core.

Thanks for the info.. I will not have access for a few days, but will get back to you.

No problem. It's possible the pressure switch could be flakey as well but with those they usually fail and shut the system off.

Good to know! Thanks again. Will let you know what I find.

Hello again,

Steve, I gained access to the car again... couldn't read the resistance charts when I magnified them, so I bypassed the thermistor.
A/C seems to work fine with thermistor bypass. so I guess I will just replace that. Do you have a good source and if we run the A/C without the thermistor to control, is intermittent use okay?

Thanks again.

Try this chart. Should show up very large if you just click on it. The thermistor controls a couple items to keep the core from icing up, You might be able to run without it but that isn't something I've ever tried as having the core freeze up isn't a good thing.

That worked to read the table. Thank you. I will check the resistance out and let you know what I find. If the resistance is correct, and the evaporator is icing up that often, what might be the cause of that?

Understood about running the A/C without the governance of the sensor. Just running it intermittently.

If it's still icing up it could be a few things. the system is slightly over or under charged. Or the air is very humid and the moisture is the problem. For the over/under charged issue the icing would occur because the refrigerant is lowing the temperature too far in both cases. Sounds strange but that is why the pressures are critical as either side of "correct" will cause similar problems.

Your generous sharing of your knowledge is invaluable, Steve. I cannot thank you enough.

It's what we do. Just can be interesting sometimes when a problem just doesn't want to be repaired.

Finally got to try for resistance....273 @ 80 degrees so I guess I will replace the thermistor. Still using A/C intermittently and still working well. Thank you again for sticking with it to the end. That was quite a puzzle!.

That would do it. The system thinks it's freezing up and shuts down then warms up just enough to work. Thank you for being diligent in tracking the problems. That is the bigger item. Thank you for using 2CarPros.