I recently replaced the condenser on the car shown and added a little oil to condenser, vacuumed and charged by weight. AC works great at idle but hi pressure falls off to about 7 or 8 bar at highway speeds (85 ambient, 65 mpg) while blowing ~50's F air at evap based on readout. In shop with gauges hooked up I see the same thing and the low side stays at 30 psi. I can bring the car back to idle and pressure goes up to 12/13 and it goes to blowing cold again. My DD (only difference is it is a diesel) blows 37dF air with 9# showing ambient 85 at 65 mph. On occasion the one I'm working through will increase in pressure slightly and blow colder air than previously although I've yet to see it below 44dF. The one working good got an a/c rebuild a couple of years ago.

No issues with the electric fan. The compressor on the car not really working is original. I'm thinking a new compressor/dryer should fix it right up?

tia

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Jim

some of those cars have had problems with the inner liner of the suction hose coming loose and collapsing inside. i've never seen it and don't know the symptoms, but it's a possibility. google it and maybe better info than me. good luck, chuck.

I added a little freon to the system and did not see any difference. Evacuate, vacuum and charge 2.25#. System calls for 2.2# and I had charged to there initially but figured I needed to add a little to account for what was in the hose.

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Jim

the variable valve maybe sticking in the compressor.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)

It's totally normal to have the condenser pressure fall off at higher vehicle speeds, increased airflow over the condenser will result in lower pressures.

Took my 98 CLK320 out for a quick trip with the diagnostics on. The air in this car is one of the best systems I've ever seen, I've got black leather on the interior and the A/C system will pull it down to a comfortable temp in under 5 minutes from fully baked in the sun with 95F ambient and 80% humidity. Kind of like Georgia weather?

My condenser pressure at idle is 14-16 bar and it falls to 8-9 at highway speed just as your car.

You mention 50's duct temps on the highway, I'm assuming its still hot inside? If the interior temps are near the setting this it's not surprising that the duct temps are not ice-cold correct?

My evaporator temp sensor stays rock steady at 38-39F, what is your evaporator temp? Also check the heater core temps, left and right. Mine are about 44-45F with the A/C in operation. If the heater valve isn't closing properly that could cause intermittent heat when you're expecting A/C.

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98 Dodge-Cummins pickup (123k)
13 GLK250 (135k)
06 E320CDI (323K)
16 C300 (62K)
82 300GD Gelaendewagen (54K)