Hi all, welcome to 2016. Does anyone happen to know where the temp sensor is mounted which activates the auxiliary electric cooling fans for the engine on the 1996 xj12. I located the sender unit for the temp gauge but can't locate the one for the fans.
Any help would be much appreciated.
Richard

 

The electrical guide should list every component and it's location.

I have not looked at the guide recently but usually a switch threaded onto the radiator tank for the older cars.

Newer cars use the ECM to control fans.

bob gauff

 

Thanks Motorcarman. Trial and error on this car after some dumb twit wired in new fans for the previous owner highlighted that he ran the wire from the A/C compressor. Hence unless I have A/C on in the car the fans don't run, and of course they switch off with the ignition. so a hot engine doe not get any additional cooling after turning the engine off, thus leaving me at risk of damage to valve seats.
Much appreciate your response.
Richard

 

Like Bob says, the cooling fan switch is threaded into the lower left of the radiator tank. It will run the aux cooling fans on low speed at about 90-100C, and high speed above 100C. The aux fans aren't needed at temps below 90C because of the huge engine-driven fan.

The temp switch will continue to run the fans after shutdown too, if the temps are within those ranges. When it's cool outside, the fans usually won't need to run after shutdown, if your system is in good shape.

I believe, and many would agree, that the cooling fans running after shutdown doesn't have a great effect of cooling down the engine parts like the heads. It only brings the temps down within the radiator, with only a small temporary air flow through the engine compartment. Eventually, the slightly cooler temps in the radiator will conduct more heat away from the hotter coolant within the engine. It seems a relatively small cooling benefit, but one that the engineers felt was necessary, or at least a good idea!

Hopefully that wiring isn't too jacked up and you can set it right.

Thank you Bob, for taking a peek over here at X305, always glad to see genuine tech advice.

 

Thanks guys, found it and plugged it back in. Disconnected the wire Mr Dummy had run to A/C compressor to check fan operation and sadly nowt. So will change that sensor out.
Reconnected wire to compressor as temp measure so I can at lest drive car. Changed my blooming expansion tank a few weeks back for a brand new one, and now I am fairly regularly showing low coolant level light, and then switching into limp home mode.
Coolant level is actually fine, temp is good, checked running car with scanner connected to give real time temp readings. Of course low coolant light and limp mode may just be coincidence, but as soon as we warm enough here in sunny Florida, to let me lie under car for a while, I will check transmission wiring.
I wish people who really don't have a clue would leave things alone.
The same guy INSISTS that my 95 xj12 cannot be ticking over on one bank only. It does, cos after it gets to working temp, it shuts down the pulse to the A bank injectors and becomes undriveable, but if you just let her tick over, she will do so for as long as you want, just at reduced rpm. I am still looking for resolution to this one.
I am again, when a little warmer, yea I'm a wimp when it comes to cold, going to check resistance across the injectors and see if any are weak. I believe ecu shuts down bank if it is unable to compensate for an odd injector resistance issue.
Anyway guys, Happy New Year and thanks again for input.
Richard

 

On warm summer days, my 96 XJ12's fans will run at low speed for a few minutes after shutdown. On very hot days, the fans will run at high speed until the computer "times" them out.

The area around my front wheel arches is usually blazing hot after an extended drive in summer, with the A/C on. The catalytic converters are mostly the blame for this excessive heat.

You're exactly correct, cooling the radiator doesn't really help the engine itself, aside from the small amount of convective flow due to the cooler fluid in the radiator.

I'm wondering if there is a way to allow the installed auxiliary water pump, or another separate electric water pump, to pump when the ECM calls for the electric fans to run when the ignition is off. That way, coolant would flow through the radiator while the fans are running and provide significantly more engine cooling after hot shutdowns.

-Nick