I have a '91 300E, and the A/C is cool, but not cold. By the sight glass in the receiver-dryer, it could use some Freon, and I also noticed that neither of the radiator fans are running. Is this normal? If not, would you please direct me to the fuse/relay I would need to check. Thanks, Dale

The fans turn on with temperature, and through the speed resistor. likely your resistor is bad (white to beige rectangular block about the size of a butane lighter, wire on each end). Replace the resistor if it is bad, and your condensor will cool, will make a big difference in temperature at the vents.

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Gone to the dark side

- Jeff

Thank you for your help. Where is the resistor located?

The resistor in my W124/300D is behind the left headlamp, next to the A/C filter/dryer.

To add detail/accuracy to my first post, the fans turn on (high) with engine temperature (105C in the diesel), or low (through the resistor) with freon pressure. Easy way to test the resistor is to apply +12v to each terminal of the resistor directly from the battery: the rear one should run the fan on low, the front one on high. If neither work, it is likely a bad fan, if only the high-speed works it is a bad resistor.

__________________

Gone to the dark side

- Jeff

Thanks, I will give it a try.

... and if the resistor is fine, fan is fine, try shorting across the high-pressure switch on the filter/dryer, that should run the fan while the A/C is on. If it does, it could be indicating a low freon charge (or a bad pressure switch).

__________________

Gone to the dark side

- Jeff