The AC speed control (manual head unit) works on speeds 1, 3, 4(high), but not on speed 2. When I switch it from 1 to 2, the blower stops and the AC light goes off. If I wait a few seconds I can press the AC button and the AC light will turn on but the blower doesn't run. If I switch to 1, 3, or 4, everything works fine.

I pulled the unit and it looks like the power connection is working fine on the speed control ****. I tested this by checking that there was connectivity from power in to one of the power out pins.

Any thoughts before I replace the head unit?

Also (if I did decide to replace the head unit) could I upgrade to an automatic one with temperature control, or is the "smarts" embedded somewhere else in the truck?

 

Most likely this is due to a bad blower motor resistor.

-Rod

 

Rod,

That was it. One of the posts, which I bet is for the 2nd speed was rusted nearly completely through. My guess it is not making any contact to - what I am assuming to be - the resistor plate. I have ordered a new one and should know by end of next week if this resolves the issue.

For posterity, I'll post a couple of pictures of the new/old one to try to help someone out in the future.

- C

 

Years ago Chrysler products had a bad habit of apparently having lose connections on the blower motor resistor sets that would arc until eventually the terminals got so hot they melted the connector plug body or they burned up the contact. I hadn't heard of that being an issue recently, but your experience has me wondering....

-Rod

 

Bad blower resistor from 2009 Dodge Ram with manual temperature control.

This is the one I replaced. It cost about $28 for Mopar part from Amazon to replace it.

Repair takes about 1 minute to remove wire and two screws.

Thanks Rod!

- C