The fan of the heater-a/c uniton my1991 range roveris not working in the II speed. The I and III speeds work just fine. Any ideas where the problem could be? Maybethe fan relay unit or a new fan blower motor? Probably not, because as i said the I and III positions work!

 

I believe there is a resistor pack that regulates the fan speeds and it sounds like one of your resistors has failed. Can't tell you where to find it though.

 

The motor itself is a one-speed DC motor. It's speed is dependent on the voltage supplied to it. The fan speed switch connects various resistors between the battery and the motor, thus varying the speed. If one speed is not working, it is either the contacts on the switch or an individual resistor is open for some reason (burned out, broken contacts, etc.) It should be fairly easy to trace the wiring from the fan speed switch back to where the resistor array is. It may be in the duct work from the fan, some are in some cars. It is more probably dirty speed switch contacts or wire connectors.

 

The blower fan resistor is probably your problem. It is located under the front lower windshield cowl on the right hand side.