Refilling R12: Can up (for gas) or Down (for liquid)? - PeachParts Mercedes-Benz Forum

400Eric · #1 08-11-2014, 01:32 PM

I've finally scored some R12! Got three 14 oz cans of the stuff!

I'm working on my older W124s (89 and my 92). If the 92 was a M119 car it would be a R134a car!

I've already done a search here and on another site which lead me to a thread which had a link to the factory manual: 83 Climate Control System

The problem is the manual still didn't answer my question! Simply put, as stated in my title, which way do I hold the can? Up for gas, or down for liquid? (Different cars have different requirements in this regard.)

I think I've already established where the low presure side is (high in the engine bay, closer to the firewall on the driver side).

Thanks to all who respond!

Regards,
Eric

pwogaman · #2 08-11-2014, 05:26 PM

Always gas, never liquid. Liquid can screw up the compressor.

97 SL320 · #3 08-12-2014, 12:35 PM

The only time you use liquid is compressor off, connected to high side and you are using a heated charging cylinder. This gets the bulk of things going and then change to gas charging from the low side.

Be sure there are no leaks before filling the system. Pulling a vacuum is a good quick test but not 100%. My 97 C280 held vac for a few days but would leak under pressure.

Dry compressed Nitrogen / CO2 works. If you don't have any try this. With compressor off, can upright for gas, fill through the low side port to some pressure around 50 PSI. Note the pressure and check in a few hours / days. Also make sure your charging set isn't leaking. It does not take much out of a can to attain test pressure on most systems.

The C280 had a corroded condenser ( the area directly behind the aux fan motors ) that would hold vac but leak the test charge in a few hours. Due to the location the leak was difficult to find with a sniffer so I ended up clamping off hoses to isolate components.

My Ranger will loose the test charge over a week or two so I'd expect it to hold a full charge over a summer. At some point it will get isolation tests / connection o ring changes but since it is mostly used for winter and global warming has taken effect, I'm in no big hurry.

400Eric · #4 08-13-2014, 04:21 AM

Thanks big time for the help guys.

I'm pretty sure that both car's systems are fine.

I haven't filled the 89's system in the over 9 years that I've owned it. It's just simply time.

The 92 has apparently also been unused for some time as well. I just found out that the "brand new" looking tires on this car are actually 14 years old!

Despite all this, both systems still have a little pressure left in them!

Do you guys agree that I have found the low pressure port?

97 SL320 · #5 08-13-2014, 06:21 AM

I don't see a picture.

The low side will be between the evaporator outlet ( car interior ) and compressor inlet.

The high side will be between the condenser outlet ( front of radiator ) and evaporator expansion valve inlet.

Sometimes the high side will be between compressor outlet and condenser inlet.

400Eric · #6 08-13-2014, 08:05 AM

I was editing my post to provide a description of where I think the low pressure port is when the site went down for maintainence. (It's also in my first post.) I think it's high in the engine bay, closer to the firewall on the driver's side.

The only other port I can find is low in the engine bay, towards the front, also on the driver's side. Sorry, no picture.

hs_300e · #7 08-13-2014, 08:56 AM

The port that is low in the engine bay in front of the compressor is the high pressure port and the one that is closer to the shock tower (also on the driver side) is the low pressure port.

400Eric · #8 08-13-2014, 09:51 AM

Thanks guys.

Regards,
Eric

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