I have a 2000 Discovery II with 140K miles. A few weeks ago while driving uphill on a dirt road at about 25 mph I noticed the high tranny oil temperature warning on. The electric fan was not working. I tested the relay, fusses, and the fan it self with 12volts, everything works fine. Whit the ac on,I tested for voltage on the fan connector and there is none going to the fan. I tested the ac high pressure line sensor and works fine. So I'm trying to figure out what other problems might be causing this. Does the ECT sensor control the electric fan?? How can I trouble shoot the ECT?? The other Temperature sensor in front of the condenser?? How do you test those 5volt sensors?? Thanks Tranny oil was changed 6 months ago and level is fine.

 

if you check the rave i believe to outside air has to be above 80 or so in order for the fan to come on

 

Did you fill the transmission with the engine running?

I would check the fluid level after the truck has sat over night and is stone cold. Start the truck run, run through all the gears and return it to park, and remove the fill pull with the engine still running and see if it's full. If no fluid drips out quickly pump more transmission fluid in there until it comes out.

And like drowssap said, the electric fan will not always come on with the A/C. There are other factors that come into play. So when you checked for power at the plug it does not necessarily mean the fan is bad, that plug does not always get power sent to it.

 

Sounds to me like one of your tranny temp sensors is acting up...Not sure what the engine electric fan has to do with it? but when your light comes on, and your engine temps are good, unplug the sensor on the cooler up front, and see if the light goes out on the dash. If not, plug it back in and then pull the sensor plug on the transfer case. your electric fan only runs when engine temps are above 210 or when AC is on with ambient temps above 80 or something...

 

Thank you all, I think I found the culprit. I unplugged the ECT (coolant sensor) turned ac on and voila, the fan was running. I still checked the oil level and it's good. I ordered a new ECT from AB for $27 and really hope this will do the trick.