Thanks in advance for viewing and throwing answer at my issue. I have a 2002 Discovery II. I've only had it a few months, and I've already fixed some of the issues a lot of you all have had such as overheating and replacing the head gaskets. This problem now isn't so bad. My condenser fan is always on, ALWAYS! I replaced the relay in the fuse box under the hood, but that didn't help. I keep it off so it wouldn't kill the battery. What is keeping the fan on and how do I fix it? My a/c cools, but it would be cooler if the fan would come on when it should. And no, my Disco doesn't overheat when the a/c is on. In fact it doesn't affect the temp very much when I do have the a/c on.

 

Well, it is designed to come on when coolant temperature reaches 212. It might be that you pinched a wire in coolant temp sensor circuit, causing ECU to believe that coolant is at or above 212 all the time. It may be that you have an air pocket in coolant. It may be that a relay is stuck. The esteemed members of this board will likely need more info to help you. Rave is your friend.

 

Ask me and i will tell you as much as i can. What more would you and the rest of the esteemed members like to know?

 

The relay that controls the fan is also in the underhood fuse box. The ECU grounds a wire to the relay, to switch it on. But that relay gets the supply voltage from the main power relay, which powers up when you turn to position 2. So if fan relay is staying on 20 minutes after truck turned off, then the contacts must be fried. If you unplug fuse 5 under the hood, it should kill power to the electric fan. See page 57 of 152 in the circuits manual for the D2.

You can swap relay with another, like washer pump, to test.

 

I assume the fan did not run all the time before you changed the gaskets. I checked Rave, but all could find is that the ECU receives an analogue 0 to 5 volt signal from the engine coolant temperature sensor.
Typically (by that I mean with most vehicles and with most ect sensors I have checked) the ect increases resistance as temperatures increase. This would would create a voltage drop (ie, 0 volts equals 6000 degrees, 5 volts equals 242 degrees below zero.) If you pinched and cut a wire during the gasket job, this would create an open circuit, or 0 volts, which the ECU would interpret as 6000 degrees, and command the condenser fan on.
I would start by pulling the ac compressor, as the wires to the ect run pretty close to that, and look for a broken or open wire there.
By run all the time, do you mean even with key off?

 

Yes it runs with the key off. I have removed fuse #5 from the fuse box under the hood. It's the only way to keep the fan off. I will look at the temp sensor under the a/c compressor to check for broken or lose wires. Thanks for the advice, I will keep you posted.

 

The same sensor runs the gauge, so if it had wiring damage it may make gauge read way off as well. If you have an OBDII scanner that can read live data it can show you the signal from that sensor and value the ECU interprests it to be. Obviously should be apbout ambient at cold start in morning.

But you could have a another wire, like the one between the relay and the ECU, that is rubbed or smashed and grounded so relay stays in.

 

Well it was a pinched wire. I removed the wiring from the temp sensor jiggled it around a bit, reconnected it and the fan didn't come on. I took the truck for a spin with the AC on, the fan turned on but turned off when I turned off the truck. Nick and Savannah, Thanks for your advice, very much appreciated.