Whats up guys? First time on this forum as this name, but was on before with my last F250. You guys were great help then, i hope it is the same now!

I got my truck this past fall (2002 F350 Dually 7.3). Got it to plow snow with. Works Great!!! Only problem i have with it is sometimes when I have the heat running for a long time, it will switch to only defrost. Now after a while it would kick back down to the setting i have selected... So for a while my feet would be cold, and then not... This does not happen all the time. Now since its nice out i'm not using the heat so i don't know how often it would happen. That being said I have no cold air with ac, or really with the vents for that matter.. The vents i'll get a little if its a cold night, but i'd assume thats normal, but i get nothing out of the ac... It does go to the vent for AC when i turn it to it, but nothing cold comes out. Just really hot air...

A parts guy told me this could be a "Air Door Actuator" problem, so I have the module for that, but no idea where it goes.. (looking for a diagram if anyone has one or knows of one). But I don't know if thats the problem.

I haven't tried just recharging the AC unit since I don't want to just waste money. Figured I'd ask u guys first.

Hope someone can help!!!!!

Thanks guys!

 

bump

 

No help guys???

 

There are a couple of things to remember about the earlier SD's and the HVAC system: The mode control (floor, vent, defrost, etc.) is controlled by a vacuum servo system, and the temperature control is handled by an electronic servo system. They are two systems that oddly have very little to do with each other other than the fact that the switches are mounted next to each other in the control panel.

So, if your truck keeps randomly blowing out of the defrost when the control is in another position, it is because there is a leak or other failure somewhere in the vacuum system, including the auto hubs if equipped.

If you are having a problem controlling the temperature of the discharge air, regardless of mode position, there is a problem with the temp control switch, the blend door actuator, or the wiring. Usually it is a blend door actuator problem, but the switches go bad too.

Hope this gives you a little help.

Jay

 

If this link works here is a cut away view of the hvac duct with item 18 being the blend door actuator. Hope this helps.http://www.partswebsite.com/fordpart...magecallout=18

 

you can try this also

 

this a part on the inside of the truck or in the motor compartment. I don't want to pull apart the wrong thing.


I'll check for leaks with the vacuum. I do plow snow so the truck does take a beating. Maybe something just finally came lose or what not.

 

I had the same issue with my vent control. This is what I did to fix it this weekend. Mine is a 99 so it might be a little different then yours. I turned the ignition on so that I could hear the vacuum pump run and find where it was. Mine is on the passengers side above the wheel well. From the vacuum pump you can fallow a short vaccuum line that goes to the reservoir. You will notice on the reservoir a line that comes out of it then T's off. One line off of the T goes toward a switch in front of the vacuum pump. It is the switch that controls the locking hubs, I think. The other line that comes off of the T starts towards the engine then turns and head towards the windshield. That is the line that controls the vents. On mine there was a connection in the line up near the windshield that I disconnected and I reran the vent line back to the reservoir. Then what I did was on the reservoir I pulled up on the 2 vacuum lines and the connector disconnected from the reservoir. I turned the connector a little and reconnected it so the only the pump vacuum line was connected to the reservoir. I then connected the vent line directly to the reservoir and now my vents work. If that didn't work i was going to figure the my vacuum line for the vent must have a hole in it but it worked. If this doesn't make sence let me know and I will try to put up some pictures of what I did.