Fan on constantly
 

AJ16 4.0L...both main rad fans come on with the ignition ...that can't be right?

Remove the 4 wire pressure switch connector on the freon line and see if it goes down to one fan operation with the key in the on position .

Reinstall if no results .

Then remove the 3 wire connector on the temperature switch on the lower aft rear of the radiator as this should give you no fans.

Will do tomorrow ..is the switch in the freon line obvious ?

It's exactly right. Both fans run in series (low speed) with ignition on, then shift to parallel (high speed) when commanded by either the AC head pressure or the radiator tank temperature.

Early X300's didn't bring the fans on until certain lower rad tank temps or a/c head pressures were achieved. High failure rates of the pressure switch in the a.c system for the lower set point trigger resulted in the fans attempting to start in high speed, blowing the fuses and resulting in overheating. So they deleted the switch and brought the fans on Low with the ignition. There was a TSB to convert the earlier cars to this methodology.
The only time you should see one fan only running is when one has failed.

You can find the relevant TSB's here: https://www.jaguarforums.com/forum/x...5/#post1927968
;-)
(Sorry Bob!)

Zane, Why didn't you post the TSBs so I would not have to????
You should have all the TSBs that I have by now.

bob

https://cimg0.ibsrv.net/gimg/www.jag...268bcf27fc.png