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?
Put the old resistor harness back on and see if it works correctly sounds like you got sold an incorrect harness to me
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.
These diagrams maybe 2 new not sure i dont have all my books with me
High speed should have nothing to do with resistor most trucks have a relay that runs high or it all goes thru the switch
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.
I think there is a wire in a wrong spot is all have seen it happen tons of times especially on older trucks where stuff has been repaired to just make it work