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W210 A/C not cooling (1996 E300)
Air conditioning not working this year--no cooling whatsoever. Worked okay last summer, and heat worked fine over the winter. I was hoping it was just low on refrigerant, but it won't accept any more through the low-side port. Compressor is original as far as I know.
CCU readings today (temps in deg C), with ambient temp 82F/27C, humidity 71%, CCU set to Auto/72F: 1 In-car temp – 33 (91F; this may be accurate, since I was driving the car in the sun for a few minutes) 2 Outside temp – 20 (obviously wrong) 3 Heater core L – 31 4 Heater core R – 31 5 Evapor temp – 30 6 Coolant temp – 83 7 Refrig press – 05 8 Refrig temp – 29 Error codes: CCU displays three error codes, which reappear after clearing and engine restart: - B1459 (series interface (K2) connection to instrument cluster) - B1422 (series interface (K1) connection to instrument cluster) - B1226 (in-car temp sensor) Other observations: - Compressor clutch engages and disengages quietly (too quietly?) when EC button pressed - No physical signs of compressor failure (leaks, burns, bad electrical connections, hissing) - EC LED does not illuminate except when button pressed - Rule out duovalve (no change in symptoms with hose clamped) - Rule out serpentine belt, tensioner, fan clutch (all replaced last year) - Rule out aux fan, blower motor controller (both recently replaced) Sensors: - CCU reading #2 is almost always 20C regardless of actual temp, but occasionally it flashes a value consistent with the LED temp display in the instrument cluster, which is accurate. This suggests the ambient temp sensor (in front bumper) works, but there's a signal problem between it and the CCU. - CCU reading #6 is almost always 105C, but occasionally it flashes a reading that matches the coolant temp gauge in the instrument cluster. - CCU #21 (engine speed sensor) always reads 25 (2500 rpm). - CCU #22 (vehicle speed sensor) always reads 50 (km/h). - In-car temp sensor appears okay physically (fan spins, wiring undamaged, receiving power), but perhaps it's generating a faulty signal I'm inclined to rule out the evaporator temperature sensor since it generally gives a reading consistent with the cores. Refrigerant pressure seems low and does not change by more than 1 bar (if at all) when EC button is pressed. I'm hoping that doesn't mean the compressor is shot. Maybe there's a blockage somewhere (expansion valve?) What are my next diagnostic steps? Thanks. Paul 1996 E300D (W210), 185K mi |
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I don't know much about A/C, but I'd always start with an evacuation followed by the correct fill. These cars are a bit touchy in terms of having the correct charge, I know our 1998 certainly is.
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1998 W210 diesel (wiped out by a texter) Baum spring compressor "for rent" |
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