Fan diode

Crusty

New member
I have been trying to fix my auxiliary fan on my 2000 xj sport with 6 cyl. As far as I know this fan has never worked with or without AC. I have tested relays, ground thermostat relay etc. with no result. The fan will run with direct current. All fuses are good. The book says check the fan diode but for the life of me I cannot find such an animal. I have removed the air box, headlights and anything else I can find but no diode not even anything orange. I could just wire a switch on the dash, but that's the easy way out, starting to be the principal of the thing, and am determined to make it work as designed. Any help is greatly appreciated.

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[h=4]Service info.

DESCRIPTION[/h]Vehicles equipped with a 2.5L/4.0L engine and air conditioning and 4.0L vehicles equipped with the "max" cooling package also have an electrical cooling fan. The fan is controlled by the cooling fan relay, which is located in the power distribution center (PDC) . For the location of relay within the PDC, refer to the label on PDC cover
The electric fan on the 2.5L engine equipped vehicles is considered the primary fan (low to moderate ambient conditions) and is energized when the JTEC receives input from the coolant temperature sensor or the a/c system and supplies ground to the cooling fan relay.
The cooling fan motor is protected by a 40 amp maxi-fuse located in the PDC. The fan relay is protected by a 15 amp fuse located in the junction block
[h=4]OPERATION[/h]Electric cooling fan 2.5L: When air conditioning is not requested, the electric fan will not come on unless the coolant temperature is at least 103° C (218° F), at which time the fan will come on and remain on until the coolant temperature drops to 99° C (210° F) or below. When air conditioning is requested (including defroster operation), the fan will cycle on and off in conjunction with the A/C compressor unless the coolant temperature is at least 97° C (207° F), at which time the fan will come on and remain on until the coolant temperature drops to 93° C (199° F) or below. Then, the cycle fan operation will resume. When the fan is scheduled to be on, the powertrain control module (PCM) provides a ground path for the fan relay. This ground is provided to the cooling fan relay through pin C2 of PCM connector C3. Battery voltage is then applied to the fan through the relay. When the fan is scheduled to be off, the PCM opens the ground path to the relay. This will prevent the cooling fan from being energized.
Electric cooling fan 4.0L: With or without A/C request the electric fan will come on only when the coolant temperature is at least 106° C (223° F), and will remain on until the coolant temperature drops to 103° C (217° F) or below. Regardless of coolant temperature, When air conditioning system pressures reach 2068.5 ± 138 kPa (300 ± 20 psi) the electric fan will engage and continue to run until the A/C system pressure drops to 1620.3 kPa (235 psi) minimum, then the electric fan will shut off.
 
Thanks for the info, not sure about the ac pressure, but the coolant temp is around 220 or so guess the engine does not get hot enough. Have yet to hear the fan, no matter what is running and for how long. Guess I'll go with "If it ain't broke, don't fix it".
 
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