hey guys if you have any info just let me know. i have a 98 dodge ram with a 5.2. air works good but it only blows on high. i thought about changing the switch but i have heard when they only blow on high there might be another problem? i just dont want to buy a new swith if thats not the problem. also my ac blows through the defrost vents now and then if i get it pretty good on the highway but thats bout the only time. my truck has that check valve that i know ive heard they dodnt have that causes that buti dont know if maybe mine is bad or something??

 

I have a 95 and I know the 98s are just about the same in many regards. Look under the dash on the passeneger's side, and locate the blower motor. You will see the lower half. It may also have a fat rubber tube that connects to the motor housing at a 90 degree angle. I am quite sure that next to the motor, held up with a few screws, there is the fan motor speed control. It contains a resistor(s) setup. That may be what has gone bad. The motors themselves are a "work or don't work" deal. They have a single set of windings. You should only see two wires going to the motor as well. Mine happen to be green and orange. It makes sense if the resistor has gone bad, the motor will run at full speed. In fact, that's what high speed is for those blowers. Full vehicle voltage. You have no resistor action to bring the voltage down. Lower volts, slower fan speed.

In the old days, the blower motors would have 3 or 4 sets of windings like a ceiling fan does. All your speed switch on the dash would do is put a full 12 volts to a specific set of windings. Each winding was a certain speed. low, med, high, etc....


Your speed selector switch is tied in with that resistor. Dodge has had a few bad circuit designs in the past. Your fan speed controller is one of them, the headlights were another.



I hope this helps. It could very well be a switch, but just thought I'd pass it along. It has happened on three Dodges I used to drive. Two 94's and my 95'

Good luck.