A/C Ex valve or drier? Or charge? Help, it's hot! - PeachParts Mercedes-Benz Forum

pdrayton · #1 05-10-2008, 03:54 PM

Yep, it's another AC question....

I've read up on the issues but can't find mine amongst them.

The problem is the ac has stopped cooling. It's an 83 240D W123 running on R12. Has been working fine for the past couple of years. Now it works for a short time and then quits. The compressor is still running but the air temps aren't dropping.

There were bubbles in the drier, and the low side was at about 2bar (22psi), while the High is stuck at about 10bar (150psi?). Manual says it should be 3-4 bar low side and 22bar high side while running at 90F ambient.

I added 12oz more R12 and the bubbles are gone. There's acutally no visible flow in the drier, but it could be it is so smooth now I can't see it.

But the high side pressure doesn't look right. It is basically stuck at about 10 bar (should be 22bar). Even when I switch the car off, the high stays high at about 10bar and the low at about 2.

Does that mean the expansion valve is stuck closed? I looked at the exValve and it is cold and has condensation on it. Is it supposed to? I tapped it with a hammer to try and loosen it up if it was stuck, but no joy.

IS that a correct diagnosis - stuck closed expansion valve? If not, what else could it be? And if it is the Ex Valve, is there any way to encourage it to work again without discharging my system? I don't have any R12 left and I don't want to go to R134a unless I have to.

I'm in florida and it's already 90 something degrees! HElp!

bobodaclown · #2 05-10-2008, 04:53 PM

Might be a stuck expansion valve. With the car off the system should equalize.

pdrayton · #3 05-10-2008, 06:54 PM

Yes, after a while, it equalized pressure to about 8 bar on hi and low (120psi). So does that mean pretty much it is the Ex valve? Damm, I don't want to lose all that R12....shhhhhhh#$$$#$!

bobodaclown · #4 05-10-2008, 10:30 PM

You can get it removed. They should credit it you, remove/replace the expansion valve yourself and have them add it back in.

TOPGUN · #5 05-10-2008, 10:51 PM

I replaced the expansion valve and dryer assembly. Vent temps are 48f to 52f. (r12 system ) I think the valve is a non equalizing type, so it will take a while to equalize. (mine does). Is it possible that your high side gauge won't go higher than 150psi? (stuck maybe) Did your low side pressure rise after you added r12? Never trust a sight glass. I have seen perfect systems running with a few bubbles going through. (flash gas) Avoid the r134 if you can. good luck.

RUN-EM · #6 05-10-2008, 11:24 PM

It is called Freeze 12 at about $11.00 a can. Will mix with any residual r12 oil/r12. See at Freeze-12.com for specks. No special license to purchase.

Regards

Run-Em

JimmyL · #7 05-10-2008, 11:48 PM

When I purchased Freeze12 it required that I have my certification...... This was 2 years ago....

Knightrider966 · #8 05-11-2008, 01:40 AM

Not to start a war here, but your in Florida and you have a local supplier for Envirosafe refrigerants there and in your state it is legal.

http://www.es-refrigerants.com This is what I'm using and I can hang meat in my car!

dannym · #9 05-11-2008, 09:54 AM

Did you say the high side should be 22bar? That would be over 300 lbs??
That sounds really high.

conecaster · #10 05-11-2008, 03:38 PM

If you need replacement gas for the R12, you can try R406a which is sold here: http://www.refrigerantsales.com/

they call it Auto Frost as well, they are the same product.

406 is an hcfc, it is a smaller molecule than R12. Its actually a combination of R22 r143 and a small amount of butane to mix the mineral oil for compatibility. I have used it successfully in cars that have limited lenght rubber hoses, like an Acura I did which worked beautifully and has not leaked. But on my e30 BMW it would not cool properly. I replaced the rubber hoses with barrier stop hoses. to keep it from leaking but it would not cool much at all, I finally figured out that the H block expansion valve is adjustable in resistance to the gas, I tighten the spring adjustment 1/4 turn tighter on the valve and and it cools great.

On a car as old as yours I would replace the rubber hoses with barrier stop hoses.

But, if you don't want to go to all that trouble, you can just buy R12 in 12 ounce cans at the same supply house, I think you can get it without a liscence through the mail from them, I have myself in the past. Its not cheap but way cheaper that $60 a pound charged by most AC shops. It should be doable for $120. Do a good vacuum check on it first, make sure its not leaking.

pdrayton · #11 05-12-2008, 12:02 PM

Thanks Guys for all the help.

Looks like the AC gods have smiled on me (touch wood).

After tapping the Ex valve I left the car over night, and the next day the AC was working better than it has in a long while. Ambient 90F and it was cooling nicely inside.

I'm hoping it will staying working well. If not, I'll investigate replacement gases. I looked at auto frost in the past, but the one gas leaking more than the other thing bugged me, and I'm not about to put barrier hoses on it if I can help it. That other stuff sounds good though. BUt then I don't think there's anything better than R12, and from what I read, the whole Ozone depletion story was madfe up by Dupont just before they lost their patent on R12, so they could stop other people making it.

Matt L · #12 05-12-2008, 12:31 PM

Quote:

Originally Posted by RUN-EM

It is called Freeze 12 at about $11.00 a can. Will mix with any residual r12 oil/r12. See at Freeze-12.com for specks. No special license to purchase.

Regards

Run-Em

It is not legal to mix hydrocarbons with R12. If you go that route, extract all of the R12 before you start.

If you mix them, you will not find anyone who will reclaim the stuff, and it is still illegal to vent any automotive refrigerant to the atmosphere. Hydrocarbon contamination is a big problem in the R12 service industry.

pdrayton · #13 06-13-2008, 09:02 AM

the envirosafe stuff is a hydrocarbon, so that means I can't mix it with my r12?

pdrayton · #14 06-13-2008, 10:14 AM

My ac has stopped working again. I poked around and found the schrader valves are leaking slightly. Damm, it was working so well, and Im' out of R12. I've ordered some enviro-safe stuff, but Ill have to wait on that.

aNyway, the question is:

Does anybody know what the lowside/high pressures should be with the car cool and compressor not running? Mine are both at 85 psi.

tangofox007 · #15 06-13-2008, 10:23 AM

Quote:

Originally Posted by pdrayton

aNyway, the question is:

Does anybody know what the lowside/high pressures should be with the car cool and compressor not running? Mine are both at 85 psi.

The pressure varies with temperature. You should see 70 psi at 70*F.

Quote:

Originally Posted by pdrayton

My ac has stopped working again.

"Stopped working" covers a lot of territory. Could you be more specific?