Thursday, December 06, 2007

Jaguar XJ40 radiator cooling fan keeps running

Yesterday, the electric cooling fan attached to the front of the radiator of our 1990 Jaguar XJ6 kept running after I turned off the ignition. This might seem insignificant as most cooling fans keep running for a short period of time after the key is removed. But this happened on a snowy day where the temperature was well below freezing. Even so, I wasn't very concerned until last night when after 30 minutes the fan was still running. Not knowing what else to do, I disconnected the negative battery cable until I could figure out what to do. That got old rather quickly.
  1. Open the hood.
  2. Open the trunk.
  3. Open the tool box.
  4. Take out a ratchet.
  5. Take out a 13 mm socket.
  6. Loosen negative cable from battery.
  7. Close hood.
  8. Place tools in tool box.
  9. Secure tool box lid.
  10. Close trunk.
That process didn't take a huge amount of time, but it did become annoying after having to manually unlock the door and trunk to get everything put back together every time I needed to drive the car (not to mention having to reset the digital clock). But then a thought occurred to me. The same thing had happened to one of our Classic SAAB 900s. At the moment, I can't remember what solved the problem, but I do remeber two parts that were involved -- a cube shaped, four prong relay switch and a temperature sensor that screwed into the side of the radiator. Having mulled over that a while, I guessed that the relay would be the easier of the two to replace. But where was it located?

The engineers responsible for the Classic 900 placed the fuses and a number of relays in a nice plastic fuse box on the top of the wheel well inside the engine compartment. I always thought that was a very convenient location. Jaguar engineers didn't have such a contraption, but they did place four relay switches together at the front of the engine compartment just behind the passenger side headlight. And whadya know, there in large block letters were the words "cooling fan."


  1. Open hood.
  2. Remove plastic relay switch cover (near back side of passenger headlight).
  3. Pull yellow relay marked "cooling fan."
  4. Reattach plastic relay switch cover.
  5. Close hood.
The best action to take would have involved me purchasing and installing a new relay switch ($28.45) and temperature sensor ($74.63). I'm fairly certain that would have solved the problem. However, European parts are not readily available at the AutoZone across the street, they would have to be ordered, and best of all it seems to be running pretty well without the relay, so I'll see how things work without it.

UPDATE (2/9/08): A replacement relay switch was purchased from North Coast Exotics for $15.09. It was installed this morning and the fan has not run at all. Hopefully, that will be the end of the problem.

1 comment:

Andy Rupert said...

I found this comment about the radiator fan:

"The radiator fan may not run, or may run with the key off, due to water entering the fan control module by wicking down the ground wire. (1990-94)"

http://consumerguideauto.howstuffworks.com/1990-to-1994-jaguar-xj6-xj12-6.htm