The cooling fan is controled by the engine computer, not the temp gauge.
Tell me what is the problem, is the vehicle over heating?
Check to make sure that both cooling fans are working with the a/c. If they are both working, (and it sounds like they are) check the fuse at location f2 in the Battery junction box. (30 amp) If that fuse is okay then you will need to check the resistor between the fuse box and the fan. The resistor is located on the radiator.
If the fuse is blown, that normally means that the cooling fans are going bad. The a/c relay side is feed with a 50 amp fuse, and when the 30 amp fuse blows then the fans are drawing too much current. The 50 amp will blow soon and when that happens you will not have any cooling for the engine.
Check to see if you are getting power to the fans when the engine is running hot. The circuit is pretty simple except that the computer turn on the fans. It is possible that the temp gauge is reading high, but the engine temp is not high enough for the computer to want to turn the fans on. The computer uses a different sensor then the gauge does. If the gauge is reading high, but the engine temp is not high then the computer will not turn the fans on.
Have you pulled the codes out of the computer?
If you have a test light, make sure that you are getting power to the cooling fan relay. Keep in mind there are two relays, one high speed one (the a/c) and the low speed one. The one that you are chasing is the low speed.
The power for that circuit runs from the battery, through a 50 amp fuse (F6), to and through engine cooling fan relay, through the 30 amp fuse (F2) through the resistor and to the fans.
If you jump the relay and the fan works, then I would be wondering if the computer is even turning on the fan.
You are right the connection should be to the resistor not the relay. I was being chased out of the shop and was typing a little faster then I should have been.
I am glad that you found it though. Good Job. I would check the current draw of the fan though, as excessive current can cause the contacts to expand and melt.