Drive home from work last night 18 miles steady 55-60 MPH no stopping and pulled onto my drive and could hear cooling fans running, weather was cold and wet. I have changed the water pump, thermostat and housing for metal one, coolant changed, radiator flushed all to no avail. any ideas why the fans are running? heater works fine, temp gauge (I know it's not accurate) sits half way up scale, no loss of coolant.

 

Here is a thread that might shed some light on your problem:

https://www.jaguarforums.com/forum/x...running-16243/

 

Check to make sure a plastic bag or other obstruction isn't stuck to your radiator.

 

Thanks, I suspect it may be an electrical fault as I have changed all mechanical parts, maybe a trip to an indy is the way to go rather than just changing sensors and hoping.

 

I know that you stated the thermostat is new, but I would check it. Had the same thing happen to me several months back, the fans seemed to be on all of the time where they had rarely come on previously, I suspected the thermostat was malfunctioning, had it changed, problem gone. Make sure the thermostat isn't installed backwards, and/or check that it is opening and closing properly. It is a more likely cause than electrical.

 

Thanks tberg, the reason I put the new thermostat, water pump and new coolant in was because the fans where running too often, they have not cured that problem. I guess I would be very unlucky to change a faulty thermostat for another faulty one. Which makes me think it may be a sensor at fault.

 

Maybe the radiator has restricted performance due to a partial blockage and needs a recore ? my high speed fans come on frequently when sat in traffic jams on hot days, but that's what they are designed to do I guess. jTIS has the temp v resistance info which will allow you to test the temp sensor off the car. If the sensor has drifted out of spec that could cause the fans to come on too early.

 

Just remember your temp gauge is useless unless you have a Realgauge installed. Can you plug in a OBDII and get a reading? That along with shooting the thermostat housing with an IR temp gun would let you know what's really going on.