Charging my A/C - PeachParts Mercedes-Benz Forum

jplinville · #1 05-17-2009, 05:16 PM

Ok, I located the label stating that the system was converted in 2001 to the R134a. i also located in the service manual when and where it was converted, and it was done at a dealer.

Having NEVER done this before, how do I charge the unit?

Jack M · #2 05-18-2009, 02:34 AM

Hi I did this about 10 months ago on my 1986 560SL that was also converted before I purchased it. I went to Pep Boys and bought the kit in the Yellow box "recharging for Dummies" It was less than $30 It came with a can of 134A, a connecting hose with a gauge attached, and a very complete instruction book. It can be purchased on line too.

It worked very well and it did use up the entire can which brought the needle into the charged location on the gauge. If you do not need the full can you can keep the can and system together and use it another time. I did a Google search on this and there was a bit of descrepancy as to whether the can should be in the upright position or inverted. I can't remember.

Now the real question is when did the AC work well last? Did it just slowly give you less cold air or did it just stop ? If you have a very slow leak that will require recharging every few years this kit will work fine . But if you have to recharge frequently then it would be best to have it gone over for other problems.

Best of Luck Jack M.

jplinville · #3 05-18-2009, 09:58 AM

Quote:

Originally Posted by Jack M

Now the real question is when did the AC work well last? Did it just slowly give you less cold air or did it just stop ? If you have a very slow leak that will require recharging every few years this kit will work fine . But if you have to recharge frequently then it would be best to have it gone over for other problems.

Best of Luck Jack M.

It hasn't worked since I bought it in September of last year. The PO, my father in law, claims that it worked in the beginning of last summer, and that he had to re-charge it every 2 years.

waybomb · #4 05-18-2009, 01:32 PM

On this subject, does somebody have a link that has the temperature/pressure charts for 134a. I can't seem to find it anywhere. Probably using the wrong search terms.

Secondly, how about a link showing the evaporator temperature / ambient temperature chart, or at least what the delta across the coil should be?

abiby · #5 05-18-2009, 11:08 PM

Quote:

Originally Posted by waybomb

On this subject, does somebody have a link that has the temperature/pressure charts for 134a. I can't seem to find it anywhere. Probably using the wrong search terms.

Secondly, how about a link showing the evaporator temperature / ambient temperature chart, or at least what the delta across the coil should be?

I've little experience with 134a, but here are a couple of links.

http://dodgeram.org/tech/repair/HVAC/R134a.htm

http://www.aircondition.com/tech/questions/95/Basic-Charging-Procedures

Matt L · #6 05-18-2009, 11:52 PM

Check to see if you have any pressure in the system first. That will give you an idea of what you're up against. If there is some pressure, you can probably get away with adding some refrigerant, although you really should attempt to find the leak.

If there is no refrigerant in the system, you might want to do it right and flush the system. That's more work than money. More money and less work if you buy a fancy flush gun, of course. In any case, if you don't have positive pressure, you should consider your dryer as expended and get a new one for sure.

djm419 · #7 05-21-2009, 08:48 AM

I have a 1983 380 SL with 104,000 miles. My Air-co is cool, but not cold. Can anyone tell me which side or connection the Freon 12 should be charged on? I don't think this system was converted? Or how could I tell if it was converted?

Pictures would be most helpfull!!

Thanks, Dan

alabbasi · #8 05-21-2009, 01:03 PM

Quote:

Originally Posted by waybomb

On this subject, does somebody have a link that has the temperature/pressure charts for 134a. I can't seem to find it anywhere. Probably using the wrong search terms.

Secondly, how about a link showing the evaporator temperature / ambient temperature chart, or at least what the delta across the coil should be?

There is a good Haynes manual that I bought that listed pressure for a number of cars up to 1989. From what I remember, I think the low side should be 40 and the high side should be about 260.

Pressure is pressure so I expect that you will need to charge to the same pressure with R134. This would mean using less R134 then you would use R12.

From what I understand, R134 has smaller molecules then R12. Because of this, new R134 hoses are lined to help seal the system. If the conversion was done on your car without changing the hoses or the seals. Then you should expect a slow leak.

Also, if converting, make sure that you evacuate the old oil and replace with oil that is compatible with R134 systems.

mbboy · #9 05-24-2009, 08:09 AM

Quote:

Originally Posted by abiby

I've little experience with 134a, but here are a couple of links.

http://dodgeram.org/tech/repair/HVAC/R134a.htm

http://www.aircondition.com/tech/questions/95/Basic-Charging-Procedures

I don't know about that first link. It says the low side pressure should be 95.3 at 85 deg. C, which seems way too high. I always thought that the low side pressure should be in the 40 range, as the second site states.

Jack M · #10 05-24-2009, 11:12 AM

HI JP Attached I hope are some photos on the driver side of the engine is the low pressure connector it has a blue cap that is unscrewed. This will reveal the connector for the charging hose.

The charging hose has a end that snaps over this connector and is spring loaded to hold it in place.

After you have correctly pierced the can of R-134 follow the instructions in the little book. The engine must be running and the AC on Full for about two minutes. at about 1500 rpm second person required. you will see the needle move on the gauge.

0-15 Blue Low Needs refrigerant open valve on can end untill the needle gets to green 25-44 Do not over fill.

If you start out with a high pressure then you will need to seek professional help. Do not add any referigerant.

This is not a problem to do. Find auto parts store and read through the directions. I uploaded some photos of the things in the box and the location of the low pressure connector. the booklet is produced by at www.wiley.com Auto A/C Recharging kit for Dummies

Get Cold.

Enjoy, Jack M.