Ventoinhas do radiador do X300

Ora, parece que encontrei o que procurava. Aqui fica para benefício do próximo. No entanto, comentários são bem-vindos. :-)

http://www.watchet.dolphins.btinternet.co.uk/8jagnotes.htm

"Fans running all the time:
The original spec on the switch (in the air conditioning line by the offside bulkhead) has it engaging the low speed fans at 12 BAR, about 175 PSI. It's purpose is/was to improve the performance of the A/C system.

For best performance, the A/C system needs to drop the pressure of the refrigerant from around 185 PSI down to 35 PSI at the expansion valve. If the ambient temps or wet conditions overcool the A/C condenser, the high side pressures drop causing a reduction in the flow of refrigerant through the evaporator. Less refrigerant to then pull heat out of the cabin.

No idea why Jaguar would have changed the system. Encouraging the engine to warm up quickly and maintaining the A/C performance makes it win/win design originally. Maintaining the fans on low all the time would seem to slow initial warm up, potentially degrade the A/C performance and induce greater wear needlessly on the fan motors.

There is a fairly simple modification that allows the fans to run more efficiently. To modify system so that fans only come on (low speed) at 86 Deg C and 100 deg C (high speed ) you will need a 12 volt relay and some suitable cable.

Cut the white link that is situated on the multiconnector by the brake cylinder and attach a length of cable to each end. Connect the cable ends across the normally open contacts of the relay.

Connect another length of cable from one side of the relay coil to a body earth point. The other side of the relay coil must be spliced into the Red/Light green cable that feeds the compressor solenoid. Mount the relay just forward of the power steering reservoir. There is a suitable earth stud nearby.

Once installed the low speed fan will only run if radiator temp. exceeds 86 Deg C. Fans will run at full speed if temp. exceeds 100 Deg C.

If the Climate control is switched on, fans will run on low speed whenever the compressor is running. "

Também aqui:
http://www.great-cars.co.uk/questions-answers/1048-jaguar-x300-cooling-fan-woes.html

"JAGUAR X300 - Cooling Fan WoesQ
I have owned my 1997 X300 3.2 for a couple of years now. It's lovely, but ever since I have had it, the cooling fans run as soon as I switch the ignition. I have replaced the engine temperature sensor as mentioned before in your magazine, but this has not rectified the issue. I initially thought it might be due to the air-conditioning being on, however when switched off the fans still run; not ideal at this time of year!
I would be grateful for any advice and maybe a wiring diagram to point me in the right direction!

A
It is in fact quite normal for the X300 cooling fans to run permanently at low speed; the original intention was, as you say, for them to come on with the air-con, but for some reason early in the production run a factory modification bridged out the air-con switch wires - a modification subsequently applied to most of the cars already on the road.
This change only affects low fan speed operation, high-speed running of the fans remains dependent on engine temperature. It is possible to change the wiring back to the original layout with no detriment to the car's cooling abilities."

Um abraço,
Jorge