2nd Gen Non-Engine/Transmission Air Defrost/Panel/Floor Switch

[AUrban]

I have a problem in my 99... when I change the positions of the dash switch for floor/defrost/panel vents, nothing happens. It keeps blowing at my feet regardless of where it is switched (a tiny bit comes out in the proper direction). If I understand correctly, changing the position of that switch triggers a vacuum diaphragm which opens/closes a door in the dash so that the air route changes. I verified that the diaphragm is moving under vacuum... . so now what?



I've read in some previous posts that I have to remove the dash in order to fix the door or hinge. Is this true?



Thanks for the help.

 

[y-knot]

The HVAC system on your truck works off of vacuum. Typically a lose of vacuum leaves the defrost only on, that is the default setting. You have a small amount of air come from the correct vent, which may be several things. My first thought would be to take a vacuum reading at the pump, it is located on the left side front. There is a service connection on the firewall wear you can sample it from, you should get at least 15cmmg I typically run 25. The majority of all the duct work is located under the dash in the center, and to get to it you Will need to remove the bottom cover and the metal backing behind it, the steering column may also need to be un-bolted from it's mount. Next I would take another vacuum reading under the dash at the 7-pin connector that goes to the selector switch. It should be the BLACK tube, that is the one from the vacuum reservoir. You have several vacuum motors that open and close the systems doors. The Defrost/floor actuator is the red and brown tubes, yellow is the panel defrost, and green is the recirculation actuator. Check that all these work and change states with the selection controller. Low vacuum, blow vacuum motor bellows, and loose vacuum tubes are the most common problems. Sometimes it may be the selector switch, good luck.

PS Low vacuum may also be caused by cruise control or 4 wheel drive CAD vacuum motor problems.

 

[AUrban]

Thanks for the reply. I'll have to run out and get myself a vacuum gauge to check the pump as you indicate. I didn't think the system was so complex but there's always something to learn. I suppose I should always remember to check all the easy stuff before pulling apart the dash.

 

[DMC]

Y-knot:



You seem to be fairly knowledgeable about this subject. I am having some similar problems with my truck. It seems that I am having a loss of power brake assist. Being that when I push and hold the brake pedal down, it will push back up and at the same moment the air will go to defrost. I have traced the problem back to the vent actuator, It is the one that is above the accelerator pedal. It wont hold vacuum when tested. When the engine is running it only holds about 10 in/hg of vacuum. I think I found the part number for this actuator (04720279) in another thread. Is this part available at other sources besides the dealer?



Thanks



Don

 

[RichK]

Open your hood and look for a small diameter black vacuum line (it's sort of has a hard plastic feel to it) running across the top of the engine wall, around the hood seal. Mine had a very obvious hole worn in it. Just run your fingers across it and you'll feel it.



Good Luck,

Rich

 

[DMC]

Thanks Rick,



I already checked the line into the cab, from the engine compartment. I have even isolated the vacuum lines in the cab from the others. I then traced the vacuum leak to the actuator that controls the defrost vent. I'm going to get a new one Monday. Unfortunately the only source that I can find for this part is the dealer.



Thanks



Don

 

[y-knot]

On our trucks Vacuum is very important, so important I run a Vacuum gage to monitor it. It controls the cruise,assist the brakes, operates all the HVAC system, and locks in the front axle for 4 wheel drive. On my truck it also operates the PAC-Brake, which I would not be without.

The whole thing is run by the Vacuum pump mounted in the front left side of the engine. There is a large black rubber line that goes from the pump to the firewall. There it T's off to feed the cruise, and T's off again to split between going inside the cab and going cross the firewall and down the right side to the top of the transfer case. Any open line of blown vacuum motor along the route will result in a lower then normal vacuum reading, so it is important to take the time and diagnose the problem. A vacuum gage is a necessity, they are relatively cheap at about 20 bucks. The first thing you should check is the vacuum pump itself, plug the gage into the rubber line before any splits and check it's reading. The pump should have around 20in/hg at idle, mine has 25. If that pans out and the pump is good, just check some of the other items one at a time. You said one of the vacuum motors under the dash was blown and will not hold vacuum, this needs to be replaced. Dodge knows about these cheap vacuum motors and has plenty of them in stock, I have replaced two in my truck, they run about 35. 00.

The vacuum lines going to the transfer case and front axle are usually suspect in low vacuum cases, they are easily broken or knocked off when going off-road or even in heavy snow areas. Good luck with your system, with the proper tools and vacuum gage it is one of the easiest systems to work on.

 

[DMC]

Thanks Y-Knot:



I too have 25 in/hg of vacuum at the pump and after all lines are hooked up prior to entering the cab. I bought one of those Mighty Vac test kits at Sears, and really like it, it has many uses. I'm going to get an actuator for the vent/defrost Monday. Do you have any part numbers for these actuators?

It looks like there may be three on the whole AC system.



Thanks



Don

 

[nuv22]

Cold Feet

ok guys so i am having the same problem as (AUrban) please read "I have a problem in my 99... when I change the positions of the dash switch for floor/defrost/panel vents, nothing happens. It keeps blowing at my feet regardless of where it is switched (a tiny bit comes out in the proper direction)" i have checked all the vacum hoses and pressure is good what next? i have a 99 and i am wondering if i have to take the dash apart ? any help would be greatly appreciated. thanks



Raul

 

[DMC]

I never did report back on this.



I ended up changing the brake booster, problem solved.



I forgot the steps to diagnose a bad booster, its in the shop manual. Mine would handle only three or four brake applications before the pedal would get hard. I would also notice right before the brake pedal would get hard I would hear the defrost door open.



I would have pulled the whole damn dash out if necessary, as I pull a good bit of heavy stuff with my truck, I sure as heck didn't enjoy the non power assist when putting my boat in the water.



Got it from NAPA... ... ... ... ... .....



Hope this helps.



Don

 

[nuv22]

hey thanks for the post don but brakes are fine over here i guess i will check the booster just incase. its just that down here in florida is nice to get in to your truck and blast the ac but not at my feet lol. i hope i dont have to pull the whole dash. anyone out there have this problem of the vent sticking in one setting?



Thanks.

 

[JPS]

HVAC problems

One simple thing you might want to check is the knob used to change position on your heater control . They have been known to crack and not turn the stem on the control. jps

 

[DMC]

NUV22:



I also checked the two actuators that I could get at with a vacuum tester, they were ok. The one that controls the vent/ac door is above the accelerator pedal. The other one is more to the right above the hump and below the kick panel. I would test both of these units before tearing out the dash, to access the other actuator that is on the passenger side.



The actuators should hold vacuum without bleeding down.



Good Luck



Don

 

[nuv22]

Thanks i will check them both today. i will keep you posted on what i find.



Thanks again



Raul

 

[nuv22]

well I checked both of the actuators and they are both ok and hold vacuum and there is no cracks on the lines. now to the FUN part out goes the dash to get to the third one. Do you guys with "dash disassembly" experience have any pointers thanks

 

[DMC]

I don't have any advice on the dash removal. But I would exhaust every other possibility before pulling the dash out. It is a pretty big job. I would make sure that all of the functions of the air management controls are not the culprit. Have you got a Dodge shop manual? Let us know how it goes.



Good Luck



Don

 

[DCMille290]

I have a simular problem, my A/C fan blows air fine from the far left vent well, the center vents, even on MAX, blows about half as much air and the right side is just so-so.

The center vents on MAX A/C fan on high, used blow well enough to feel them in the back seat. The fan sounds like it should be blasting air from the vents, but it isn't.

Checked for leaks, don't see anything. Any ideas anyone?



Thanks,

DC Miller

 

[Melkers]

Great! I just came down with the same problem. 4X4 functions, just all the air through defroster vents. will look into if this weekend.

Rai in Pueblo

 

[Melkers]

Went out and checked the "easy" checks under the hood. DARN, there's a lot of "vacuum hose lookin'" stuff under the hood! But I did get a opportunity to clean off all the other hoses. All looked O. K. but now I have an excuse to get a mityvac tool. Thanks,

Rai

 

[djbobo]

Melkers



Since yours is on the defalt DEFROST setting I would check the auctuater near the center hump on the drivers side. I've personally done two.



It's going to be alote easier to take the plastic shroud off under the steering wheel and also the metal cross brace.



The air motor has a yellow (I think) air hose you can pull off & test with your thumb for vacuum while you select between the floor & defrost. If you have any vacuum remove the motor being carefull with the plastic post attatching the motors arm. If you break it just drill a 1/8" hole and put in a 6/32 screw . The arm has a offset so take note which way faces. That's my guess anyway.



dj