95 E320 aux fan craziness

[J. M. van Swaay]

About a month ago, I replaced a defective aux fan with a new one manufactured by ACM of Germany. (part number 000 500 8593) After completing the work, I jumpered the freon pressure switch to verify operation. Both fans started spinning--I was happy with another maintenance item completed.

A few days ago, I noticed running temperature a little higher than what I would expect. I suspected it might be time for a viscous fan clutch. So, to diagnose the problem, I let the car run for a while to warm things up. As expected, both aux fans came on at about 110 C. In order to get things just a slight bit warmer (to check the viscous fan clutch) I put a piece of newspaper in front of the grill. Instead of sucking the paper to the grill, the fan I installed a month ago blew the paper back at me. I checked about ten times, and sure enough, the fan was running in the wrong direction. I looked closely at the directional arrows on the black plastic bullet shaped part of the fan and they confirmed that the fan was indeed running in the wrong direction.

I stood there for a while and scratched my head. I remember from installing the fan that the plug could only be installed one way. It was simply not possible to reverse polarity. A quick search of this forum revealed that this is not the first time this has happened.

I removed the fan, disassembled the black plastic plug, swapped the pins around, reassembled the plug, (no cut and solder required) and reinstalled the fan. It now runs in the direction indicated by the arrows.

Go figure.......

J. M. van Swaay