1998 E300d AC Pressure Switch mystery

[tudor8]

Hello all
My car has a four pin pressure switch while the dealer tells me that based on my VIN I need a three pin one. Has anyone run into this problem before?
If yes, would you mind sharing the part number. I'm fairly certain I need a new pressure switch.
Thanks!

 

[Lyserman]

Is this the sensor that sits at the bottom of the condensor by the radiator?

 

[tudor8]

It's the sensor on the receiver/drier. here are a couple pictures I took:
The sensor is the shiny round thing at the bottom:

Here's a picture of the connector:

I ran the engine and shorted two pins on the connector, which resulted in the auxiliary fans starting to run. That tells me that once the pressure reaches a certain value, those fans should run. On my car though, those fans never ran, no matter how hot the engine got or how long I ran the AC.
The system was recharged and checked for leaks recently, so the pressure is where it should be.
In addition, the AC seems to work properly only when driving on the highway; if I'm stuck in traffic, it doesn't cool properly, and like I said, the aux fans don't run, most likely because the pressure switch doesn't do what it's supposed to do.
That's what led me to the conclusion that the pressure switch is defective.

 

[Lyserman]

The reason I asked was because the temperature sensor at the bottom of the condenser is sometimes referred to as a pressure switch. Mine has 4 pins even though the EPC say 3 for my VIN.
If you put your VIN here I can see if I can get the part number for a 4 pin pressure sensor.

 

[tudor8]

Thanks so much!
WDB2102251A622084

What's strange is that I don't see a sensor on the condenser.

 

[Dec]

I don’t know its exact function or how it relates to the auxiliary fan other than that it’s a fan control module, on a w202 its located behind the wheel arch liner as in picture below, don’t know where its located on a W210, its in an odd location and seems to be in need of keeping cool judging by the cooling fines on the casing of the unit.

Might be worth checking it out and its wiring plug, it can be opened via the 4 hex head screws on the back of the unit.

Example… MERCEDES CLK W208/C W202/E W210 GENUINE AUXILIARY FAN CONTROL UNIT A0255455332 | eBay

Also… 98 99 W210 E320 4 Matic A 0275458132 Auxiliary Fan Control Relay Module ESG400 | eBay

Dec

 

[tudor8]

Thanks Dec, I need to check that out later today. It's possible that my car doesn't have the module, because I traced the fan wiring all the way back to the relay box on the driver side (left side of the car). I'll check it out nonetheless and will report back here.

 

[Dec]

You do seem to have one alright, 89 in the diagram in link below.
APPARATUS CASE AND CONTROL UNITS. Fits: Mercedes | Mercedes-Benz of South Atlanta

89. CONTROL UNIT. EGS CONTROL UNIT.
Required: 001
AUXILIARY FAN

Also... 128.SENDER UNIT.
Required: 001
PRESSURE SENSOR



Dec

 

[tudor8]

Thanks for the diagram.
I checked behind the bumper (driver side) and there's no control module. Even if there was one, I wouldn't suspect it to be defective since the fans start as soon as I short-circuit the pressure switch.
I went to the dealership, and they can't figure out what the correct sensor is either.
I might have to remove it and read the part # on it, if it's still there.
Thanks for trying to help anyway!