HVAC issue....

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

loki223

Senior Member
Joined
Apr 11, 2012
Posts
746
Reaction score
105
Location
Spokane, WA
Ram Year
2018
Engine
Cummins 6.7
Well, i've been looking around and haven't seen anything with this issue. First off, i know my blower motor resistor needs to be replaced, (works great on high...thats about it...) but thats not the issue i am curious about. On the heater/cooler dial, they both work great, but right in the middle is the only spot where the temperature changes. There is just one click, where it goes from hot, to cold. doesn't matter where the dial is at past the click, you get the same temp coming out of the vents. Switching all the vents work, AC works, and heater works, but there is no variation. Its either hot, or one click over, cold. I have never ran into an issue like this before, so i am curious if anyone has some ideas? is it somehow connected to the blower motor resister? (because that would be awesome since i plan on replacing it anyways) or is there something else that i should dig into while i am under there?
 

Bigtman07

Registered User
Joined
Jun 28, 2010
Posts
9,329
Reaction score
287
Location
Piqua, Ohio
Ram Year
2000
Engine
Cummins 5.9
Well from my understanding. This may be wrong but I think it would explain your issue. In 1999 dodge changed from a vac powered blend door system to a stepper motor driven system like what is in all the newer trucks. So hat is most likely happening is one of 2 things maybe both. The stepper motor may be going bad and that it only can read only on and off and not the variations.

OR

The switch in the dash is having issues. It can't send the proper signals to the stepper motor so it doesn't know how to act. I'm not sure really how to check to see which one on that.
 
OP
OP
loki223

loki223

Senior Member
Joined
Apr 11, 2012
Posts
746
Reaction score
105
Location
Spokane, WA
Ram Year
2018
Engine
Cummins 6.7
Hmm, well if its the controller i suppose a wiring diagram and a volt meter would be handy. I would assume the signal should change in the wire being sent from the controller to the motor depending on where the knob is. if it only changes in one position, that controller is bad, if it changes throughout all the knob positions, than its the motor. At least that's what i would assume? i am by no means an electrician, i can do all my own wiring but stuff like this i start guessing. lol
 

Trupiano

Registered User
Joined
Jun 27, 2010
Posts
10,981
Reaction score
725
Location
Hometown : Puyallup,WA Stationed : Little Rock,
Ram Year
2010 Ram 2500 6.7L CTD Crew Cab
Engine
6.7L CTD
Like Tony said it could be the blend door, but it sounds more like it could be the switch. The switch is basically just a potentiometer, and they can go bad over time. Like you said, I start with the simplest thing. Take your switch off and clean it out. Then test the signal and see what she gives you.
 

Bigtman07

Registered User
Joined
Jun 28, 2010
Posts
9,329
Reaction score
287
Location
Piqua, Ohio
Ram Year
2000
Engine
Cummins 5.9
^^^I'll agree. If I had the stepper system I would try to help ya with voltages and what not but alas I have the cable version.
 
Top