My 2002 xj8 have new problem both cooling fan doesn't work at all even when turning on the AC , it only works when the temperature hit 222F then it brings it down to 200 and stop working again . What may cause this problem? Could it be faulty temperature sensor?

 

This suggests that one of your fans is not working. When yo get the fan(s) running, is it only one or both?

If one fan is not running for some reason, the other good fan cannot run in Low fan speed mode (at between 194 and 187F) so you get no cooling at all by fans in this temp range. The good fan will run (alone) only when the mode is switched to High fan speed at around 210F. The High speed will be switched off at 200F and, after that, the fans would normally stay at Low speed which you don't have at present so there is nothing.

Check whether, when the fan(s) is/are switched "on", only one fan is running or both. If only one fan running, check the fuse of the non-running fan and, if fuse good, check whether this fan has perhaps seized. If not seized (can easily be turned by hand) test it by connecting 12V supply directly to it.

 

They both work at the same time at the high speed checked fuses all are good

 

In that case, the relay that controls the fans (and their Low & High speeds) is likely faulty. Or, perhaps, there is a bad contact in its connector. The relay is as shown on the picture below and it is somewhere lower down in the front LHS corner of the engine compartment. Perhaps you can first try with unplugging and plugging back in the relay connector. If no change, try with another relay.

 

Thanks a lot for the help . Did try another relay but nothing changed , my mechanic friend told me I have a solution he did splice the relay wires and add another relay and another 30amp fuse ! now both fans work as it should temperature is around 195-210F with AC on . My car Has 150k miles I didn't mind splice and doing some electrical work