Unsuccessful attempt to recharge A/C - PeachParts Mercedes-Benz Forum

cewyattjr · #1 05-25-2007, 03:30 PM

So the '82 MB appears to have been converted to R134a, given the appearance of those retrofit nozzles.

Weather got warm today, and the A/C has not been cooling at all, so I went down and picked up one of those "all in one" recharge canisters with the built-in meter.

As directed, ran engine, max A/C, plugged into low-pressure valve, squeezed the trigger. Looked as if it was taking a charge. Then... did I hear something (?). Not sure, removed recharge hose and found that gas was leaking straight out of the low-pressure valve.

Assuming failure of this valve is what is the issue here -- is that a common problem?

Bad idea to take a road trip if there is no gas in the system? Compressor might seize from lack of lubricant?

Thanks,

Chuck

Jadavis · #2 05-25-2007, 03:49 PM

I believe the EC button on the CCU is for economy, meaning that it leaves the AC turned off.

-Jim

winmutt · #3 05-25-2007, 04:03 PM

Try finding another conversion valve. I had one from the freeze12 kit that I had that just sucked donkey nuts. I got some new r134 type conv valves from pepboys and worked like a champ. When you do fill up next make sure you put the oil in first.

If you want to prevent accidental operation, you can unplug the low pressure switch power.

Bill Ladd · #4 05-25-2007, 04:34 PM

I just did a complete AC system rebuild and wound up converting to 134. The low side conversion port is supposed to just thread onto the existing port. Not so with my system.

When I did this, it pushed in and bent the r12 needle valve preventing a proper seal. Once I removed the r12 needle valve, the 134 port threaded on nice and snug and made an effective seal.

Hope this helps.

NAPA and CarQuest will have the conversion ports on the shelf.

cewyattjr · #5 05-25-2007, 08:47 PM

OK, spent another half hour or so fiddling with this. I have one of those all in one trigger rechargers with the pressure meter on top. With the A/C "on," not in EC mode, I see almost no pressure when trying to recharge. When I switch it back to EC, I'm getting significantly more pressure in the line. Even appears as "charged" at that point, and I can feel pressure from the valve when I engage/disengage the charge connector.

Why would the line be more pressurized with the A/C off and drop when the compressor is supposed to be on? Symptom of a bum compressor?

When switching A/C, I can hear what sounds like a "click" under the hood, and I check the pressure, and it drops considerably and doesn't appear to be "taking" the charge.

Sure is hot today!

-Chuck

Knightrider966 · #6 05-25-2007, 08:55 PM

Your using the wrong AC fill system! Those all in one trigger unit's are junk. I've never gotten one to work yet, but they leak like a sieve. As far as your AC pump is concerned, you will not get the pump to come on unless you get some pressure into the system first. Your can of Refrigerant will turn cold when it is being inducted into the system properly. However, too much oil in your system will reduce it's effectiveness for cooling. This could be your problem since refrigerant leaks are usually gaseous and not liquid and refrigerant oil will remain oil even at atmospheric temps.

cewyattjr · #7 05-25-2007, 08:58 PM

So it fits the retro-fit add-on connector, but I should use a different fill type unit?

Knightrider966 · #8 05-25-2007, 09:07 PM

I have yet to find one of those pistol trigger dispensers to work right yet! But I have had the cap assembly blast off into space once with a big BANG! Get the hose that screws onto the top of the can, with the gauge if you like. It will help. When refrigerant is being sucked into your system, the can will go cold. The only other thing I've found is that sometimes the last person to do a conversion will not remove the Schrader valve in the original fitting and that can cause a recharge delay. You would have to remove the retrofit fitting first to find out, but try what I told you first. Try Phoenix for hot sometime! 103* in the shade so far this summer. It will get hotter!

cewyattjr · #9 05-25-2007, 09:17 PM

Yeah, we're wimps here in New England, the minute it gets above 90 people complain. But it is usually a humid heat with no air movement. I moved up here from South Texas in '87. Everything in Texas has A/C, on the gulf coast we'd get a breeze which helps too!

Still 90+ degrees in May is wEiRd.

Thanks for the tips! So I shouldn't think it is weird that I get pressure on that gauge with the A/C off, and no pressure when I kick it on? That seemed pretty odd to me even with the crappy connector.

Knightrider966 · #10 05-25-2007, 09:22 PM

NO. I think what is happening to you here is the trigger mechanism is stuck and not opening all the way. that's what happened to me and when I tried to get it to dispense right, it blew the top off and shot it 40 feet into the air! Trust me, get the hose with the brass ends and even though it will cost you more, it is unlikely that it would burst apart and hurt you in the process. It sounds like there is some pressure in your system if the pump is coming on when you turn on the system though.

It's the trigger release on the top of the can that can be a real ***** though. It sounds like your connector is making a lock to the suction side, but your dispense valve on the can doesn't work. If it's that plastic thing, well there's no suprise!

Carrameow · #11 05-25-2007, 09:23 PM

I remember for some strange reason that the W123 is a goofy system to try to charge from empty..anyone else feel the same way. Now instead of trusting the pressure switch, I always "hand fire" the clutch with 12VDC from the battery

speace · #12 05-25-2007, 09:25 PM

Quote:

Originally Posted by cewyattjr

Why would the line be more pressurized with the A/C off and drop when the compressor is supposed to be on? Symptom of a bum compressor?

When switching A/C, I can hear what sounds like a "click" under the hood, and I check the pressure, and it drops considerably and doesn't appear to be "taking" the charge.

-Chuck

I'm not an A/C Pro, but have recharged several systems over the years. The pressure on the "low" side will most always increase when the compressor cuts out. Actually that is a good indicator that the compressor is working!
At rest, the high and low pressures will eventually equalize and the pressure will be more than the "normal" operating pressure for the "low" side. I use a "Manifold" type gauge set from Autozone that lets me see both the high and low sides.

Good Luck!

Regarding not "Taking" the charge: I would guess you don't have a good path from the can to the inlet valve. You will have to inspect all pieces of the charging kit. It could be the can isn't opening, the valve won't let the gas out, the hose isn't depressing the schroeder valve.

Knightrider966 · #13 05-25-2007, 09:28 PM

Quote:

Originally Posted by Carrameow

I remember for some strange reason that the W123 is a goofy system to try to charge from empty..anyone else feel the same way. Now instead of trusting the pressure switch, I always "hand fire" the clutch with 12VDC from the battery

I would not recommend that! If the clutch suddenly seizes, you will have no fuse protection whatsoever and you could have a real problem. If your in doubt about the pressure switch, just pull the leads and jump them together. That's a lot easier and less risky!

Carrameow · #14 05-26-2007, 12:56 AM

Quote:

Originally Posted by Knightrider966

I would not recommend that! If the clutch suddenly seizes, you will have no fuse protection whatsoever and you could have a real problem. If your in doubt about the pressure switch, just pull the leads and jump them together. That's a lot easier and less risky!

yeah whatever works.
Anyway quite seriously I dont recommend the manifold guages. Some may say this is outrageous, but I believe it to be true. Whats funny is that combinations of different fittings, the schrader valves and manifold knobs on various cheap sets can be mismanufactured and are actually blocking the R134 instaed of admitting R134.
I'm serious.
Even some good people dont understand the schrader functionality especially when you adding on the R134 adapters.
Sometimes you actually have to remove the schraeder needle points from your manifold hose lines--especially the middle line--because they are not "pressing against anything". Check your setup and think it through.
Also, I once had two sets of identical AC guages from Interdynamics. One set of knobs on one manifold worked the opposite of the set on the other manifold. I am serious.
I always get good results by thinking the system through and finding the low pressure side -- thats always the side thats accepting the return from your evaporator after it has done its "cooling thing" in your passenger cabin. The pressurized R134 gases have expanded and done their thermodynamic thing, and this expansion produces a huge temperature drop where the intensely cooled condenser sucks the heat and humidity out of your cabin...
Disassemble, flush and pull a vacuum on the system and feed the R134 straight from a can using one of those short discharge lines that come with the 16 ounce cans to the low side of the compressor on the LP tap. Use 2 16 oz cans. Those manifold guages? Unless you are a real pro and have really good ones, all they actually do is cause more trouble and cause leaks and allow the vacuum you have pulled in your system to escape. I always put my oil right into a hose when I have the system dissasembled and flushed.

rbardolv · #15 05-26-2007, 01:04 AM

....and that would explain why, when I tried putting in some oil charge to my system my can tap gauge showed 115lbs from the can and was going no where else.... Its those damn valves not even touching and / or doing anything... Yeah that was a waste of a good can of oil charge. Got all over the damn place too!

I guess Ill go fiddle with those valves and make them work properly.