International 4900 Heater Blower motor won't operate at medium speed

PeterG said:

I have a 1990 International 4900 dump truck. The cab heat blower motor would not work in the middle speed, just low and high. Then the fan starting making noise. I cleaned the whole system out of Mice debris. Then the blower only worked on high, and then starting not working but going on only once in awhile. I thought it was a bad connection. I have replaced, the fan motor, the resistor, the resistor harness, and the fan switch. It now works great on low and high! Can't get it to run at the middle speed. On the new resistor harness, there are 4 wires. On the truck, only three wires. Does this have anything to do with the middle speed. Not a big deal, I can live with low and high speed for defrost or cab heat, but considering I have replaced everything, what am I missing? Any International 4900 experts out there?

Click to expand...

PeterG said:

I bought the resistor from the Dealer, and it seemed like it only ran on High. I bought another resistor online that came with a harness. I installed the new harness and resistor yesterday and the new fan switch and got low and high. On the new harness there are 4 wires. Three on top, one below. On the truck wires, there was never any wire running to the lower one below.

Click to expand...

PeterG said:

Thanks for your help. I will look at it again later today. Not really a big deal, unless you think that it means something might burn out. I just need heat/defrost high fan. The truck is old, and nothing is that great.

Click to expand...