Painting radiator fan motors on a Citroën SM.

(And no, just owning an SM is not the worst automotive decision, but owning 2 of them might be.)

While swapping in a new radiator, I removed the metal cans on the radiator fan motors and painted them, because pretty. I put them back on wrong and swapped the polarity of the magnets. The fans then ran backwards and I didn’t notice.   

The symptoms were befuddling:  Engine temp would be ok around town in traffic, but if I got on the highway with the fans running, they’d block air flow and I’d overheat. Other times I could get on the highway before the engine temp turned the fans on and the car would run great on the highway.

I thought maybe a thermostat was intermittently sticking, so I replaced that. I ended up replacing the radiator again, flushed the system, numerous times, etc. (Removing and replacing the radiator is about a 4 hour job.) I’d pretty much given up after a month of troubleshooting and wrenching in my free time and decided it had to be a head gasket, head or block coolant leak. Then one night in my garage wearing flip flops (which I normally never do), I suddenly realized while standing in front of the running car that my feet were being blasted by super hot air. The discovery was both relieving and annoying.

15 minutes later the fan leads were swapped with a solder gun and swears. It wasn’t worth it, but those fan motor cans sure do look pretty.