Cadillac Club Estonia

I had similar problem with a fan control module for radiator fans. on my 1985 fleetwood should be same on your model. Module sits behind headlight and basically takes the BCM fan signal and amplifies it to control the speed of the radiator fans. This module also has a feedback signal back to the BCM so it knows if fans are rotating and speed. I was able to fix the module as the parts that go in them are the power FET transistors mounted to the heatsink. I replaced with
Intersel 76137P N channel Power FETS x 4 transistors needed. It looks to me like the originals just do not quite have the current capacity for the two fans. If the fans get a bit sticky they cause more current to draw through the control module and pop the transistors.
Here is datasheet. http://html.alldatasheet.com/html-pd...UF76137P3.html

Just open up module and replace the 4 transistors on the heatsink with above and you have a better speed control module than new. These FET's are rated 75A at 30V x 4 lots of current. Also note the heatsink has fan voltage on it so it should be isolated from touching any chassis ground or it would blow the transistors. A cheap fix couple dollars for the parts a solder iron and good as new. Also check for corrosion inside on the foil as water seems to get in.