2009 dodge ram 2500 diesel, no a/c blower. Have traced wiring back to blower switch and find no voltage supplied to the switch. Does voltage come directly from the ignition switch?

 

Power goes from the TIPM to the blower motor first, then thru the resistor block, and then to the switch. Switch provides ground path. See if you are getting power TO the blower motor.

 

 

That's normal. The fan will always run at a very low speed, just to keep airflow thru the cab.

 

 

If you turn off the climate control panel with the "Mode" switch do you still notice air moving from the blower? I took a look at the wiring diagram and HeyYou is correct, there is not "Off" setting for the 4-position fan speed control. Every available path has some amount of series resistance to ground and therefore would be providing some amount of blower motor power. The four settings are Low, MD1, MD2, and High.

-Rod

 

 

Per the wiring diagram, when the climate control system is in the OFF position the ground path for the blower motor is removed from the blower motor circuit. If the blower motor is still running, albeit slowly, when the climate control is OFF, that would suggest you are getting a completed ground path between some or all of the resistors on the blower motor resistor and actual ground. The issue could be due to the blower motor resistor, but could also be within the climate control head.

Is the blower moving more/less/about the same amount of air in the OFF setting as it does in the LOW fan speed setting?

-Rod

 

 

You can access the wiring diagram for the HVAC system by selecting the appropriate information from this site. Considering the diagram for the 2001 Ram 2500, when the climate control is "OFF" the ground path for the blower motor should be open. With that in mind, the approach I would recommend taking is to disconnect the blower motor resistor connect (since it's probably easiest to get to) and set the climate control to OFF. Use a multimeter or test light to check for continuity to ground on the Black/Tan wire. Is there is no continuity to ground on that wire, check the other wires for completeness. If there is not continuity to ground on any of the wires, then check for continuity to ground with the terminals on the blower motor resistor. There doesn't appear to actually be any means of that resistor block being grounded other than through the connector, so I would expect you will not find any continuity to ground on the resistor connections.

Assuming you have continuity to ground of one of the wires, then the next step would be to disconnect the climate control unit and repeat the test. If you still find continuity to ground on one the wires, the issue is a short in your wiring harness between the control head and the resistor block. If you do not have continuity to ground on the wiring harness, then the issue would be with the control head.

If you do not have continuity to ground on any of the wires with the control head OFF and plugged in and you do not have continuity to ground of the resistor block itself, then there is no ground path for the blower motor when OFF is selected and the blower motor should not be running. If that's the case, reconnect everything and find a garage or similar where you can remove outside wind/breeze as a factor and see if you are still getting definite air flow through the vents. If you believe you are, disconnect the blower motor resistor and see if it changes the flow of air. If so, post back as things would be VERY strange and require more thought.

Later model years (such as the 2009 in the first post of this thread) do not have an "OFF" position for the blower motor control. Are you sure yours is a 2001?

-Rod