ok i have put 3 12oz 134a cans plus oil charge and a/c is still not cool enough. low pressure is higher than red (high pressure gage) high prssure is not much above 150 psi, no leaks, do i need to add another can? i retrofitted my 1983 300sd, 190K miles last year with new compressor, dryer, switch, o rings, expansion valve. worked fine until 134a fitting started leaking, then lost all 134a, put new fittings on and now i am having the above problems. i am starting to really hate this car! it is a money pit! but i can not afford another one right now and i need cool a/c for my job! help!!!!

Well that's a novel problem!! Sounds like one of two things. Don't laugh, but check your gauge hookup, try a different gauge. High side of 150psi is a tad low. I don't know how to interpret low pressure being above red on gauge. What is the low side PSI reading? If low side is as high as you say then you might have overcharged the system. How quickly is the compressor cycling? Is it making any funny noises? If low side remains high after correcting the amount of charge, then the compressor is not giving you enough suction. I hope you didn't put in any of that stop leak stuff. The worst case scenario is that both high and low are equal (bad expansion valve, orifice tube). Many possibilities here..

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Jeff Lawrence
1987 300e
1989 300e
1987 BMW 325

Two things, never add more charge than a clear sight glass with the car running...Also with the gauges, you are not getting into the high side valve. I have had this stump techs. You will have to correct the valving. Do not overfill with 134. Be sure to run the auxillary fans on high by bypassing the fan resistor and updating the fuse.

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Benzmac:
Donnie Drummonds
1992 500E (very soon I hope :)
1981 280GE SWB
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM

Benzmac, what do you mean by update the fuse? is this a simple 20 amp vs 15 amp in the fuse box under the hood?
i replaced /updated high pressure fan switch on reciever dryer. also turned out i had the wheels on the manifold gage turned on instead of off (it pays to re-read instructions!). now i am getting more reasonable measures of 30 psi low side and 225 psi high side, it is still not cool enough though, should i add more 134a to get measures around a 45psi low and 325 psi high? what should temp be with a thermometer stuck in the vent inside the car 45 degrees?
thanks