Charging the A/C - PeachParts Mercedes-Benz Forum

190D22 · #1 04-21-2002, 07:47 PM

I have a 1984 190D 2.2 with 138k+ miles on it. I have verrified it is low on R12 refridgerant and I would like to add some. I have 7, 12oz cans of R12 and the filling hoze. Through the viewing window I had a white foam appear and a few bubbles here and there once it ran for about 30 seconds. I don't want to use half a can and have to throw it away, you know since the stuff is very expensive and almost impossible to find today since it's illegal. Any thoughts and the procedure? Never recharged this car before... Thanks!

Mike Murrell · #2 04-21-2002, 09:41 PM

It's not illegal. You must have a 609 certification to buy it.

The only way you know with certainty if the system is properly charged is to use gauges. Even with gauges, you may take less than a full can. Some folks charge with the sight glass, but that can be misleading. Often times the system is overcharged when using this technique. If you overcharge, the interior of your car will not cool well because the high pressure switch will cycle off the compressor. When the system is overcharged, you'll hear/feel the compressor cyling on and off too often.

190D22 · #3 04-21-2002, 09:56 PM

so how do I go about recharging it correctly without being forced to convert my system? My father has helped my brother charge his system with the same hoze and his AC works perfectly fine... Thanks for the reply!

stevebfl · #4 04-22-2002, 08:04 AM

Well, the proper way is to retrieve what is in the system and then recharge by weight.

janko · #5 04-22-2002, 09:32 AM

steve, can one approximate the correct proceedure and recharge by monitoring pressure on the low and high side? and if so, what values should one use for these pressures? thank you.

190D22 · #6 04-22-2002, 02:21 PM

Well, the place near me that does AC charging will not work with R12, they will convert your system if it is R12 and then charge. So I don't really want to do that, what would you do in my position?

Mike Richards · #7 04-22-2002, 09:07 PM

If the A/C shop near you won't work on an existing R-12 system it's likely because they are not qualified/certified. As stated above, you need a 609 certification and more to handle this refrigerant.

If this is the ONLY shop you care to deal with and you already have the R-12 and the little do-it-yourselfer hose, then I'd say you may want to give it a shot yourself. If the system is bone dry, determine how much the unit holds. Check SEARCH facility here. You may even find capacity charts at http://www.aircondition.com.

If it's not bone dry, but just needs replenishment, start out with a can. As stated above, gauges are better, but if all you have is the diyer hose, you're options are limited. Watch the sight glass AND have a thermometer in the center vent. Crank up the air volume. If the system has some charge in it, let it cool a bit before you start charging. I've always wrapped a hot cloth(dip in hot water 1st) around the can
before I open the valve. This helps the refrigerant to flow better.

You may as well accept the fact that whether you do it, or someone else does it, you're most likely going to have some R-12 left over and as you know, it will leak out of the can.

190D22 · #8 04-22-2002, 09:34 PM

Hey thanks a lot for the reply. That's what I've been wanting to know all long! I'll give it a shot when I have time. Thanks again!

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