In the cold months I disconnect the engine cooling fans by pulling out the "white plug" we all know about, why, because I don't think they should run constantly . Anyway while checking out other things under the hood, engine running at operating temp the fans came on at low speed. I was under the impression the both fans were disabled once that plug was disconnected. My thoughts now are the fans active at a given temp. at least at the lower speed. So my question is since my fans operate without that pluged whats the story on it??

 

I did some analysis of the fans control circuits a while back and published it in this post

https://www.jaguarforums.com/forum/x...ircuit-282963/


My conclusion was that even with the bypass plug disconnected, the fans would run at low speed at 86 Deg C, and High Speed at 100 Deg C (Ground connection for the low/high speed relays through Radiator Thermostatic switch).

 

The 'jumper' is on the A/C pressure circuit, it has nothing to do with the engine cooling circuit.

 

From what I understand is the white plug jumper work around less full TSB freon low working A / C pressure switch ( not under pressure ) complete line removal different freon line part # ( less 2 wire freon pressure switch ) is to prevent both fans coming on at the same time blowing the fan motor fuse ( s ) , then you're behind the curve on engine block cooling

There is a fuse upgrading TSB as the first productions may only have 1 fan power fuse and later production has 2 fuses so that brings about more questions

True the other command on by the 86 / 100 C coolant temp switch does bring the fans on but fuse blowing negates this coolant temp determainant working

I was confused for a while if both fans run at low speed and both high speed or left runs high and then both sides high like mine but may be explained by the 2 different part #s for the white colored X300 specific fans control relay module different then the black X308 module , X308 slightly different and doesn't work on the X300

I found my original X300 fans control relay module was mounted upside down allowing water to pass through connector fusing a relay contact inside when sawing the module apart , you could shake and hear water rattle inside

 

So if i don't turn on my AC the cooling fans will run like a normal car, turning on & off via the sensor.

 

Low speed fans = BOTH FANS IN SERIES
High speed fans = BOTH FANS IN PARALLEL.

Both fans will always run when they are commanded ON
There is no one fans runs while the other is off.

They are BOTH ON or BOTH OFF!

 

Correct , although all cars have this sort of radiator fans 2 modes of control , A / C cooling load demand in relationship with higher freon pressure and the direct coolant temp sensor or in the X300 case a 86 / 100 C low / high mode 3 wire switch sticking in the radiator

There is a simple test of the fans relay control module that gives high and low fans mode to confirm that ( jumpers the temp switch connector so seperate test )

Motorcarman , My confusion comes from the time of complete both kidneys failure ( sudden kidney stone ) and the medical task / coordination / time / effort involved , eyes being one of them as wished they made the car in brail at times , eyes recovered to be able to drive after a couple of years fortunetly

Kidney failure effects brain function ( dirty blood in brain ) along with baes line mistakes or accurate keeping track of mechanical observations tinkering around , but keeps me mentaly active and mentaly exersised along with eyes reading

My father wants me to dispose of the Jaguar but he doesn't know I'm a winner , his loss