URGENT. Need Help With HVAC
 

Hi I am a long time listener and first time poster.

I have a 2007 Ram 3500 with a 5.9, Laramie.

I have now taken the dash out 4 times trying to figure out this problem

Truck has dual climate control switch which I replaced, I replaced the doors with HeaterTreater doors, none seemed to be broken. all motors checked with a 9v battery each way. I have the pelm out right now and am trying to bench test it to figure it out

First, the recirc door does not work at all, the switch will light up and no door movement either way.

Second, the top door which will make the air blow in your face or towards the defrost vents, if I set it up to be closed mechanically and on the switch and start going from face to defrost about 10 times it will open about 1/2 way and close about 1/4 until it gets stuck in the open (vent) position.

the other heat/cool doors also do some moment when I am doing the second test and it seems the doors just move where they want in no particular order.

The truck is supposed to self calibrate the doors every 20 or so starts, this has not happened for me. I am at the end of my ropes with this and need some advice what to do.

does anyone know if there is a separate computer that controls the HVAC? is it part of the TIPM? I cant keep throwing parts at this..

Thanks in advance for any help you may have

Brian

I have been going thru something similar and have emailed the Heater Treater guys and they have gone well above what they should or needed to do with me in trouble shooting and I thank them for it! I replaced my recirc,blend and mode 1 doors. The recirc door broke a few years ago and I blocked off inside. 6-8 weeks ago I had AC and then next morning when I left I had no ac. Truck was stuck in HEAT mode and would cook you in no time flat. I thought the blend door had broke as it was not moving. So I ordered the kit and replaced the recirc and blend and decided to do the mode 1 since I was already that far into it. After putting it all back together the recirc doors works but doesn't always move to where I thought it should be according to my mode switch. Heater Treater tells me the truck can move the recirc door to use inside or outside air according to some conditions it senses. My blend door is still stuck on full hot and will not move to cool no way no how. The actuator motor tests good on the bench. If you pull the batteries off the truck it should force it to do a recalibration when you fire things back up. I have did this with no luck. I had more then the 20 starts with no recalibration luck. Heater Treater in the beginning told me the control head (the part in the dash that has your on off fan switch and blend and mode knobs) usually works or goes out fully. This is the computer that controls the calibration of the doors. After further discussions with them they conclude that its either a bad wire between the blend motor and control unit or the control unit has a bad spot in it not making the blend door work right.
I have not ordered a new control unit yet for my 2005. My parts store can get one for 140$ exchange. I recently got a new actuator motor for the blend door but have not put it on yet either. I can take off the actuator motor and manually move my blend door and things work the way they should. Nice cold AC or good heat.




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I have figured my problem, after sleeping on it and starting again this morning I figure I would test the motors again, with the same problem happening and still plugged into the truck I started to use the 9v to test the doors, as I tested the blend motor I noticed my mode door moving also. Bingo. I took all the tape off the harness that is connected to the hvac box and found 2 wires disconnected. This is about in the middle of the box area where about 5 or so wires join together with a shitty crimp. I soldered the wires back together and now everything worked properly. the recirc door never did anything still so I removed the motor and put it back on with the door in the middle, now everything is working properly.

Nice find!

Am not familiar with the Dodge system, are there position sensors built into the actuators? My thought is that that part of it may be the most prone to failure.

it just uses dc motors, when the door opens/closes all the way it puts voltage on the motor and the system senses this voltage/torque and stops the motor. This is how the system knows when its in position, the little plastic stops tend to break off when this torque is applied and causes the doors to fail(flop around) the heatertreater doors are made of steel with metal stops which will fix this once and for all. my problem with the broken wires caused the doors to not open or close all the way causing me hvac problems, low heat, heat only on one side, when set to defrost air came from all the vents.

That's a good find! I may take my control head off this next weekend and check it. Makes sense to me after what all Heater Treater was telling me and I suspect I have a wire acting up also. As long as its not down lower below the connections.




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Just posting a reply to an old post here................Last spring I had my dash doors start to break. The recirc door was the problem but ordered the heater treater kit and redid all the doors. After doing that I was still not happy with the AC and noticed my blend door (HOT/COLD) wasn't working and would default to HOT upon start up of the truck. I had not noticed this as it had been winter and one of my first times to run the AC in the spring showed a problem of what I thought was a door issue.


I had talked with heater treater who was great with answering all my questions of what it could be. They said the little servo motors rarely go out. I had checked wiring to the blend door and was fine and the heater treater test lead they sent verified my servo was moving the blend door. I also noticed that I was getting some air out of the various modes but nothing that impressed me. April 2016 I decided to buy a new control head. The head that has your knobs to turn the HVAC on and off that fits into the center of the dash. It was back ordered and I just now got the new control head!!!!!!!!!!! Swapped it out. Took 5 minutes. It went thru about 1 minute of calibration. Lights blinking on it which wasn't something I noticed on my old control head. Heard the new heater treater doors moving in the dash and after it was done I must say this AC works better then it ever has in my truck since I bought it 4 years ago used (2005 2500). I am getting a lot of air moving thru all the various modes. Even the infinite settings between some of the modes is working where they didn't before. As far as I know there is still a national back order on this part. I kept checking with my parts store and they finally called a sales rep who managed to find one for me in a matter of days after all this time waiting. This part cost me 140$ with a 200$ core charge so they must be having a high failure rate on these control heads and want them back for repair! I was hoping to keep the old one and open it up to see what failed but had to turn it back in for 200$.


To get me by this summer I had an old plug that I wired a 9volt connector to and then plugged into my blend door servo. I then used the 9volt to move the door back and forth for what I needed. These servo motors move with 12 volts and they reverse the polarity to go back the other way., For some reason my control head would just move the blend door to HOT upon starting the truck.


Anyhow just wanted to let everyone know what it was for me to help trouble shoot in the future. It could be a door failure, wiring issue like the other member had or in my case a door and control head failure together.




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