I checked and added R134A this morning until the air was nice and cold. It took one full can. The pressure was 185/22. Does this sound close to a full charge?

BD

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87 560 SL
93 300E 2.8
91 300CE-24

At what RPM were pressures taken?
Aux. fan on/off?
Ambient outside temp.?

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The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)

The pressures were taken at idle (600 rpm), at 80 degrees. The aux. fan was off. I dont think that my pressure switch works.

Thanks...

BD

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87 560 SL
93 300E 2.8
91 300CE-24

I would say you are still light. I always charge by weight but the high side pressures could do to be higher. The pressure switch is 290psi. Obviously most cars are there a significant amount of time. A system is too full when the fan won't bring the pressure instantly down from 290.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

Thanks for your help...we will have another look at it today.

BD

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87 560 SL
93 300E 2.8
91 300CE-24

It's best to run at about 1,500 RPM with doors and windows closed and a/c on full at max fan speed for five minutes. After five minutes, pressures should be stabilized. Under these conditions the pressure you gave would be a little light. You will probably have to experiment some, every system is different. Use a vent thermometer and try to get about fifty degrees or a little higher under the above conditions. Going down the road at highway speed before the cabin begins to cool, causing the system to cut back, should result in vent temp below 50.

Good luck,