Hello everybody.

I've exhausted about every repair manual and professional pay service I can find. I'm having an A/C problem in my '93 E300 turbodiesel. Today I checked it, charge was low so I vacuumed it, added dye & re-charged. Don't see any leaks at the moment. The A/C hasn't worked in this car since I bought it. Currently, the A/C blows HOT on the drivers side, and ~55*F on the pass side. I've ran thru the diag codes in the climate control display, no issues there. I've scanned it with my big Autel and it brings up a code for coolant pump. I should have written it down, but I figured I'd clear it and see if it comes back. The factory service manuals listed in Identifix are kinda useless. Can anybody point me in the right direction of where to start??


Also, fans: It looks like the drivers side electric fan is an electric fan, and does the fan on the pass side actually do nothing? What is tit's purpose? I noted that with the A/C on sitting in the shop, coolant temp creeps up well past 80*C, but doesn't make it to the next line up. I plan to check out the fan clutch next, but I wanted to verify how the electric fans operate first before I condemn the fan clutch.

Is it a '93 or is it a W210? The 210's didn't show up until the '96 year model in the US. The HVAC systems are vastly different between the two.

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Blowing hot on one side indicates a control issue. Not sure what the mechanism is, but sounds like and air control door is stuck. If vacuum, it's probably a blown pod/actuator or a bad vac control switch. If electronic, blown servo motor on the air door.

The OP is low on refrigerant. You need a good set of gauges and a temp/pressure chart when charging the AC. There's a chance the duo valve is busted but thats easy enough to check by clamping off the heater hose.

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It's a 98, sorry. Typo

MCallahan, I went thru the diagnosis steps in the control panel to check all of the vacuum bellows and everything there seems to be working correctly.

Tjts1, I've seen that on other cars with dual climate control, low refrigerant causing air to be cold on one side, not on the other. I don't think that's my issue here. I don't remember how much refrigerant I put in, but I typed into the machine however much the sticker said.

When was the machine last calibrated?

Are you getting any hissing sound from the center dash when the AC is on? My expansion valve hisses very loudly when it's low on refrigerant. I think gauges and TP chart is more reliable way of charging the AC. On the w210 when refrigerant is low, it's always the driver's side that runs hot.

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No idea on calibration. Sitting here fully charged, with questionable fans, I'm seeing ~40 psi low, ~240-280 psi high. Hence why I was looking into fan issues first. I don't notice any hissing sound, no.

The driver side fan has a motor. The passenger side fan is driven by a belt off the driver side fan.

Sixto
98 E320s sedan and wagon
02 C320 wagon

Sounds like your duovalve is letting hot water pass on the drivers side. How is the ac when you start the car cold first thing in the morning?

FYI Mercedes w210 does not use a blend door to direct air through/around the heater core like most other cars. All the air passes across the heater core. An electric valve regulates the flow of hot coolant into the heater core to selectively warm the air passing through the hvac system. The w210 uses a duovalve so it can seperately warm the drivers side and passenger side of the heater core. Try clamping off the heater hose feeding the duovalve. If the ac works ok, then diagnose the duovalve to determine whether you have a control problem or a failed duovalve. Given the age of the car, most likely it is the latter, but best to be sure before throwing parts at it. Good luck.

"FYI Mercedes w210 does not use a blend door to direct air through/around the heater core like most other cars.*"

Pretty sure the 124 works the same way, just single control. Thanks. Had a Volvo that lost a blend door servo and did exactly this. Sure sounds like a control issue more than an AC issue, though.

You can also do a sensor test for heater core temp in max cooling mode.

Sixto
98 E320s sedan and wagon
02 C320 wagon