Last September, I bought a 1991 300E from my brother-in-law (who bought it from his father). It has always been well maintained and is just under 90k.

It wasn’t until this summer that I noticed that the a/c is useless when outside temps go over 70. Fans and everything else seem to work fine, but the a/c has never been charged in its fourteen-year life. I have a couple of cans of Du Pont Freon 12 that were recently purchased by a friend who is certified to do so. I also have the proper charging hose to fit the R12 low side service port.

Considering that the system holds a little over two pounds of Freon, can I safely dispense at least one 12oz. can into the system without the use of a pressure gauge? I’m assuming that to have almost no coolness to the abundantly blowing air that the system must be short at least 12oz. or more. Am I naïve about the possibility of overcharging?

Also, it seems that the low side valve is very handy – facing up at about 3” from the right side edge the air filter. Is this correct?

R-12 can be charged to a fairly accurate capacity using the sight glass on the reciever/drier.
Do a search on "sight glass" or "eye-sight"

Should come up with needed info.

Don't ruin your a/c system with that junk. R12 is getting less and less expensive and you can get a license for $15 and a few hours work by going to www.imaca.org. You can then buy R12. I just bought a 30 pound jug for $14.06 per pound. You can get it in smaller quantities on ebay or elsewhere once you get the license.

Good luck,

[QUOTE=LarryBible]Don't ruin your a/c system with that junk.

He has Dupont R-12 [dichlorodifluoromethane]
What is JUNK about Dupont R-12 .. it is exact replacement.

R-12 is not junk. He must have had a senior moment.

__________________
1981 300D 147k
1998 VW Jetta Tdi 320k
2001 Dodge Ram 2500 141k
1979 300D 234k (sold)
1984 300D "Astor" 262k(sold)
Mercedes How-To and Repair Pictorials
I love the smell of diesel smoke in my hair

Larry, I believe I have the right stuff.

It is IG-LO Du Pont Freon 12
(dichlorodifluoromethane CCI2F2)

Sorry, I sure thought that it said Freeze 12. That's what I get for perusing quickly instead studying a post.

Good luck,