Hi there
>
> I have a 1988 JEEP Cherokee Pioneer 4.0 litre. It is an American spec
> model, first purchased in Virginia & then exported to England. It has
> aircon fitted. The chassis number is: 1JCMR7820JT050336.
>
> When I purchased the Jeep the engine auxilary electric cooling fan was
> missing. It had seized on the previous owner & he had removed it but
> not bothered replacing it. I have now bought a replacement fan but am
> having problems with the electrics, as they seem to have been
> damaged/wrongly connected by the previous owner.
>
> My questions are;
>
> 1) What colour are the two wires from the loom to the fan connector
> and where is the loom connector for the fan located?
It should be two wires to a plug that reaches pretty close to the top of the fan: Red with White trace (hot) and Black (gnd). Both run thru the loom to the relay panel on the left fender behind the airbox. The relay is the forward-most relay.
2) What colour are the wires from the loom to the radiator temperature
> switch and where is the loom connector for the switch located?
The radiator switch is on the lower left side of the radiator (looking forward from the cab). The wires are a Yellow from the ignition switch that is hot (12 volts) in the RUN or START position, 0 otherwise. The other side of the switch is Gray with a White trace which goes to the Fan Diode Assembly (2 steering diodes). The FDA has a Green with White trace lead that goes to the fan relay coil and an Orange lead to the A/C clutch relay.
3) What voltages should I expect at each of the fan relay (LHS fender)0 volts on terminals except #1 - that one is hot to the battery at all times.
> wire connections under the following conditions
> i) Ignition off.
ii) Ignition on/Engine cold/aircon off
Same as i)
iii) Ignition on/engine hot/&or airson on.
Three cases here. a. Ignition on, engine cold: same as i) b. Ignition on, A/C on, any temp: Terminal #2 (relay coil) will be battery voltage - about .6 volts (1 diode drop) and Terminal #1 will be at battery voltage. c. Ignition on, A/C in any position, temp above (about) 210 F: same as b.
4) Is there a wiring diagram available online for this vehicle
> anywhere (I have a Chiltons manual, but it does not show the
> electrical layout clearly)
Certainly. (Now I bet you want to know where ).
This is from the Factory Service Manual, but I'm not sure you can get that anymore. I find the Haynes manuals to have better wiring diagrams than Chiltons.
Test procedure: unplug the radiator temp sensor. Turn the ignition on and short across the temp sensor plug. Fan should run with the key on. Ignition on, turn the heater control the the defroster position and the fan should run. The diode assy could easily be the problem although a bad relay would be more likely, especially if the original fan seized. In the same vein, there is a fuse wire ( Green) on the power distribution center (on the other fender) that would likely be blown if the old fan seized.
If it gets too grim, email me and I'll scan the FSM schematics for you. The MJ is the same as your XJ under the hood.