Hi there folks. My 96 XJR was sitting for a week and suddenly my cooling fans came on at 3AM in the morning. Glad I heard them, so I disconnected battery to wait until later in morning to source issue.

Checked the archives and read quite a bit about this but didn't really come up with a solution.

Here's what I've done with car cold and ignition off. I reconnected battery of course and fans started running on cold engine with ignition off ...

1. Disconnected the temp sender only, that is mounted on bottom of radiator and the fans kept running without turning on ignition. Then Reconnected sender.

2. Disconnected temp sender only, which is mounted on the engine (2 wire) and fans kept running without turning on ignition. Then Reconnected sender

3. Disconnected large relay only which is behind the front bumper/driving lights and fans stopped running without turning on ignition. Reconnected Relay and fans started running again.

4. Disconnected the temp sender only, which is on the A/C line and fans stopped running without turning on ignition. Reconnected sender and fans started running again.

All of this is with stone cold engine and ignition turned off.

If anyone has experienced a similar condition and found a solution, please respond as I've read quite a bit about this and am just as puzzled now as before. I will try throwing parts at it firstly by replacing the large Relay which I have on order currently.

Any help and or suggestions are truly appreciated. My fans are wired with the modification so that they run all the time when ignition is turned on. In the meantime I just pulled a fuse and that stopped the fans.

Thanks gang ... Grant ... West Coast Canada

 

Maybe the "temp sender which is on the A/C line" is actually the refrigerant triple pressure switch? I would suspect that device.

 

Hey there RADS:

Thanks for your reply and help. I believe you are correct and that valve is called a Trinary Valve. Your suggestion is well taken and I'm leaning towards replacing that item. Just trying to find a supplier for a new one. There are a couple used on eBay but I don't know if I would trust a used one. For anyone that is interested the number that is on the unit is LNA7657 AB.

Will keep the forum posted as I find/replace these items.

Thanks again to RADS

Sincerely, ... Grant ...

 

Grant,
Just a thought, but does your car have a trinary valve? If memory serves, it was dropped in favour of a simpler solution before 1996, with the upshot that the fans came on at low speed as soon as the ignition is switched on. Not a very elegant factory initiated change, but there you have it. There is another thread on here about a popular modification whereby a simple modification allows the fans only to come on when the AC is on, but that is probably not something for you to be thinking about at the moment.
You have been very logical in your tracing of the fault, and I think the relay is the more likely culprit. The fan circuit has power so that the fans can run with the ignition off, and I do not believe that the AC can trigger the high speed fans directly, so a faulty relay would be my bet.
Good luck!

 

Hey there CountyJag:

Thanks for your reply and explanation about the Cooling fans operation with regard to the AC. Yes I have the trinary valve and also the modification whereby the fans always come on at low speed and run constantly when ignition is switched on, only to come on at high speed when the system calls for it.

I've ordered the large Relay behind the bumper on left side (Drivers Side in Canada), as well ordered the Trinary valve just in case. Both from eBay and hoping one of those items will be the culprit. I'm going to try the newer Relay that is on the XJ8's as there is a much larger supply of them. Everything seems the same on the relay other than the color. Mine is white, and the newer ones are black. Some suppliers indicate the newer Relay will work just fine. All the contacts are numbered the same and it looks like it will plug in exactly like mine, hope they are correct.

Thanks again for reaching out to explain to me a little more about the operation of the system. I'm understanding this better all the time with the kind help from this wonderful forum.

Sincerely, ... Grant ...