OMG!!!!!

First time in a week that I have been able to work the Scorpio.  On my to do list is to wrap up the inspection / testing of the cooling system.  I had already drained and filled the radiator, installed a new thermostat, inspected and tested the clutch fan, and swapped out the coolant temp gauge sending unit.  The only thing left was to verify the operation of the electric fan in front of the radiator.

On the Scorpio there are two fans in operation.  The clutch fan driven by belts, and an electric fan in front of the radiator which is controlled by a thermostat in the radiator.  On this early model Scorpio the fan actually has two speeds.  On later models they did away with the low speed and just had an on/off switch. 

Testing should have been simple.  Jumper the thermostat switch so that the fan will come on.  I did that 1st thing this morning and no dice.  I then got out my handy dandy shop manual and electric and vacuum troubleshooting guide to diagnose the issue. 

Problem #1:  Even though the shop manual is for the 88 model year, it already had the switch to a single speed fan in the literature.

Problem #2:  The electrical and vacuum troubleshooting manual shows correct wiring schematics but has no troubleshooting steps for the fan.  It simply states refer to shop manual for diagnosis.  Great.

I spent most of the morning going through the steps trying to diagnose why the fan wouldn't come on.  At first I thought it was a relay issue.  Found out I was testing it incorrectly.  I had at one point or another disconnected and reconnected every part of the circuit for the cooling fan to operate.  The best I could come up with, was a bad connection between the relay and the thermostat switch.  At the end of the day I decided to test again in the fuse / relay box.  I tested between fuse #8 and the fan relay for continuity and it was fine.  I made a leap of logic that since the shop manual only tested for continuity for the troubleshooting maybe I should check for voltage also.  This is where I found my problem.  The wiring diagram shows that fuse #11 has power all of the time for the fan to work, but fuse #8 which is for the coil side of the relay only has power when the "car is in the run" position.  When I turned the key to run and tested fuse #8, no power. 

At this point I am starting to wonder if there was problem in the wiring for fuse #8 and what in the heck was I going to do about it.  Almost as an after thought I decided to start the car and test for voltage again.

You guessed it, 12v at fuse #8 when "the car is running".  I guess the manual was a little vague about this and I made an assumption that when the key was in the "run" position the fan would turn on if told to do so.

Nope,

I jumpered the switch and started the car.  The electric fan came right on.  Wow what a long day for a small payoff :)  Anyway, the fan was a bit loud, so i will take it apart and lube it up, but it should be good to go!

Next up, speed sensor. 

Later,

Darren