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I have no evidence my car is overheating but I have never heard my electric fans running even on a hot day. My V12 has an aux fan that runs when I shut the car down on a hot day but the XK8 never has. I am going to let the car idle and see if they ever come on just sitting on a warm day idling. Shouldn’t they kick on then?
I have no evidence my car is overheating but I have never heard my electric fans running even on a hot day. My V12 has an aux fan that runs when I shut the car down on a hot day but the XK8 never has. I am going to let the car idle and see if they ever come on just sitting on a warm day idling. Shouldn’t they kick on then?
If you plan to do that first get an OBD tool that can tell you the actual coolant temp as the dash gauge tends not to come on till around engine destruction.
Off the top of my head the fuse locations are the same between the X100 and X308 . Clean the thermister connector as a bad or dirty connector mimics colder then true temp to the ECU which provides the command grounds to the relay module . Thermostat change as a insurance policy as they fail to the closed position
Last edited by Lady Penelope; 05-22-2018 at 09:22 PM.
Thank you for your responses but my fans are in fact running correctly. When the fan on my V12 is running you hear it on the XK8 you don't. I had the hood up and actually looked at it with a flashlight before I could tell it was running... my bad.
My recollection is that for the later 4.2L cars, the fan are controlled by PWM to run at the speed the ECU deems necessary. It is no longer an off/low/high type of control. So the fans can be running, but low enough you do not hear it.
Agreed. Last year when I got my car I figured the fans ( or the controller ) were broken; but with help from the folks here and some observation with a good flashlight , I know they work as they are supposed ....just VERY quietly
Looking at the diagram (Thanks BTW) I think the ECU grounds might be mislabeled. What is labeled as "Right only" Should be BOTH FANS IN SERIES" (low speed) and "Both" should be labeled as BOTH FANS IN PARALLEL (high speed).
When RIGHT ONLY is grounded by the ECU, the top relay closes allowing power from Fuse #12 (73) through the RH fan, through the the now closed relay, then down to the normally closed (NO) to common (C) contacts of the middle relay, out to the LH fan to ground. This sends power through one fan and then the other, thus putting both fans in series. This would make each fan see only 6v (instead of 12) and run at approximately half speed.
When BOTH is grounded by the ECU, the middle and bottom relays close. Fuse #12 (73) supplies power to RH fan, then around the top relay to the bottom relay (now closed) Common to ground. Fuse #14 (74) supplies power through the now closed middle relay to the LH fan and to ground. This gives both fans 12v allowing them to run full speed.
Just a bit of clarification. I'm troubleshooting a problem in this area and was trying to figure out the wiring.your drawing helped bunches...thanks!
05-22-2018, 12:16 PM
Cooling fans
