dude....

the 2 pole connector is the reading that feeds to the fan. Its based upon resistance and the lower the resistance, the faster the fan runs.

The single pole connector should be the one that feed the temperature information to the cluster.

How to find out?

get a multimeter and measure the resistance across the 2 pole on the sensor. It should change from a very high ohm reading to a very low ohm reading as the car heat up. If you say when you plug your connector in the sensor, the fan spin high, my guess is your reading should be almost zero thus the car computer thinks the car is way hot!

If however, the ohm reading is not low, (sorry I don't have the temp Vs resistance table for your car) and is verying from a very high number to a low number as the car warm up, than you may have a different problem. When I say very high, I am refering to something in the thousands and very low means something in the low hundreds. Perhalps you can use the W140 temp. V resistance table for reference.

I think someone here post such readings for the 124 before, do a search.

One thing, your car has the 2 pole and the single pole connector integrated into one sensor. Unlike W140 where we have seperate sensors. If your cluster is reading with the right temperature, that should mean your sensor is not broken. As I say I am no expert in 124, nor 140, just trying to help you. It would be difficult to think the sensor is half broken!

if you think the new sensor is not expensive, just chnge it and see!

BTW, did you check the refrig. sensor switch?