I've got a 2003 2wd Dually with the 5.9 High Output Cummins and 6 speed Trans. My problem is that when I try to change the vents from Dash to Foot or Defroster (or any combination) they don't change, it just keeps blowing out the Dash vents. I can turn the blower off and cycle the vent controls all the way in both directions and sometimes it will cause it to switch to one or the other. Also, the Hot/Cold switch has the same problem. It will be blowing cold air but I can cycle the switch several times back and forth and finaly a hear thud sound and it starts to blow warm air. I've been told it was caused by a vacuum leak, then I took it to guy who supposedly knows about these things and he said it was all electric and that my truck doesn't even have a vacuum pump on it. My questions are this:

 

1. Do my climate controls run off vacuum ?

        A. If yes, then where the h@#l is the vacuum pump ?

        B. If no, then what do you think is causing my problem ?

 

Any help would be appreciated. Thanks.

All electric. I do believe it is the controllee but not certain. Its been a couple of years since ive dealt with this issue

On your 03 the vacuum pump is by the passenger side firewall. When you turn he key on you should hear it click on for a second. I do believe he only use for it was for cruise.

Go here……………..http://www.heatertreater.net

 

 

Good product;  I've replaced the "recirculation door" and the "blend door" on my .04.5

Edited January 1, 201411 yr by dorkweed

The bled door is electric in the passenger's foot well.  Heater Treater only deals with the blend door fix. 

The air vent outlet is vacuum controlled.  If it fails it goes to the default DEFROST.  The selector is over the hump near the driver's foot.   

On the 3rd gens, all the 'doors" (recirculation, blend/temp and mode) are controlled by DC motors.  THERE ARE NO VACUUM CONTROLS!!!!

Recirc door is a common failure because the moror keeps turning when the door is against the stop

Recirc door is a common failure because the moror keeps turning when the door is against the stop

 

Actually, the "stop" breaks off because it's cheap plastic that breaks over time.  After the stops breaks, there's nothing for the ECM to "index" the motor against.  The HeaterTreater doors are metal with metal connections and stops that connect to the DC motors.

Would that cause the vents not to switch from Dash to Defroster/floor and vise versa ?

No a broken recirc usually block air flow

Would that cause the vents not to switch from Dash to Defroster/floor and vise versa ?

Yes. That would be the "mode" door that is broken. Actually it's the stop/indexing pin that's broken. Mode being the change from the panel to the floor to the windshield etc.  I've not replaced that one yet on my truck, because it still is fine.

No a broken recirc usually block air flow

Not on the 3rd gens……………………it will just stay in either the recirculation mode or the fresh mode.  It will NOT block air flow……………..I know, I had to change the door on my truck. I still had "air" prior to the fix.

My problem is not just the vents, it's also the Temp control. I have to cycle the switch several times to get it to start blowing warm air. Is it likely that I have 2 seperate problems, or possible that both are caused by a single problem.

 

P.S. I hate to keep beating a dead horse on this, but after the different responces so far, I don't know any more than I did when I started. I'm fairly certain now that my problem is electrical, but I have no idea what to do about it.

Go to the link I posted prior;  you'll find what's wrong, I guarantee it.  It tells you specifically what is wrong and explains it a lot better than I can.  If I can do it, you can also.

Not on the 3rd gens……………………it will just stay in either the recirculation mode or the fresh mode. It will NOT block air flow……………..I know, I had to change the door on my truck. I still had "air" prior to the fix.

Yes it will. Happened on my 06 and my dads 06. Plus many others that i fixed qt the dealer. The door falls down ontop of he fan and blocks most of the air.

Edited January 2, 201411 yr by mopartechnician

Yes it will. Happened on my 06 and my dads 06. Plus many others that i fixed qt the dealer. The door falls down ontop of he fan and blocks most of the air.

I know that this is a month old but thought I would chime in. I agree that Heater Treater will fix the broken recirc door and that a broken door will block most of the air flow and needs to be removed/replaced. I don't think that the OP has door issues that are causing all his problems though and needs to be looking at the electrical/vacuum issue as well.

My air will actually change from Dash to Defroster, and even to the floor vents, but I have to fiddle with the knobs for several minutes to get to change. I was told it was likely a vacuum leak, and that the vacuum pump was electric, only to find out later that the 03's dont even have a vacuum pump, everything is electrical.

I am almost certain you have a vacuum pump. The 03s had them but your hvac controls are electric. Atleast the 03s i have seen are that way. The pump will be up by the airbox its a black and orange pump if i remember right

I'll say it again…………….the controls for the HVAC doors on the 3rd gens are all controlled by DC electric motors!!!!

Dorkweed is correct. All DC motors.  I used the heatertreater fix. Get all the doors and replace them. My 03 did the exact same thing but now everything works nice. All their doors are metal. It is a pain to get in there to fix so that is why I say replace them all so you only do it once.

Dorkweed is correct. All DC motors.  I used the heatertreater fix. Get all the doors and replace them. My 03 did the exact same thing but now everything works nice. All their doors are metal. It is a pain to get in there to fix so that is why I say replace them all so you only do it once.

 

 

This^^^^^^