heater fan speeds

[JMD]

Hi All
I have a 1963 MK2 3.4 which has always only had the one speed on the heater fan working.
Before I start pulling out the entire heater box to get at the motor I was wondering if it might just be the resistor that is fitted onto the side of the fan motor body.
Can anyone give me any advise on how to go about testing the resistor . I have a voltmeter but not sure how to do thiis..

thanks
James

[Doherto]

James, I have just measured my resistor at 2 Ohms although I have not disconnected it from the circuit. I suggest that if only one speed is working, and the resistor is faulty, you will only have full speed fan. If you only have slow speed fan then the resistor is ok and you have another problem. Basically from what I see on the circuit diagram, 12 volts is supplied to the motor for full speed, and 12 volts via the resistor, which drops the voltage, and spins the motor slower. On your meter you should have a selector which can measure Ohms, turn this to the lowest setting and place across the resistor, if no resistance is measured then its open circuit and needs changing. If it is not then set your meter to 12volts DC and measure the voltage from each side of the resistor to earth. If you have 12 volts on one side and something less on the other its ok. 12 volts on one side and nothing on the other it needs changing. Tony D

[Doherto]

James, just to clarify, measure the resister on Ohms without the heater switch being on. Then switch on the ignition, and heater switch in both positions, to test the voltages. Tony D