Blend Door

[RMHanes]

Have a '98.5 D2500 Quad Cab manual with about 178,000 miles and it is a manual transmission. Picked up from having state inspection done and the blend door only stays in the Defrost setting. Noticed that the selector knob was way easier to switch than before. Recall that the repair might involve removing the dashboard but nothing much more than that. Would like some links to the repair, know that there have been a few with this same repair, time to do the repair and anything else that might need to look at while the dash is apart.

 

[KATOOM]

https://heatertreater.net/dodge-ram-02-08

 

[BigPapa]

Sounds like you lost your vacuum. Did you lose your cruise, too?

Check your vacuum lines from the vacuum pump to the firewall. The OE lines are plastic and are now old enough that they’re VERY brittle, easily broken.

-Scott

 

[KATOOM]

Sounds like you lost your vacuum

I agree... My bad as I stopped reading when the question was about the blend door. It clearly sounds like a vacuum issue. The blend door only controls hot/cold setting not vent location.

 

[Joe Mc]

Had the same problem. At least on my 99 the arm (plastic) on the actuator has a split push tab that inserts into the arm on the door. One of the split tabs broke and the arm kept coming out. My fix, although a PIA, was less of a PIA than removing the dash... I drilled a hole in the arm eliminating the tab, inserted a small screw with a washer on each side of the arm for support, locked it in place with a nut, slid the screw into the door/arm and threaded a poly lock nut onto the screw. Must have been 5+ years ago. All work was done from the driver side floor, very tight quarters even with the seat all the way back.

 

[BigPapa]

Well, did you find the problem?

-Scott

 

[RMHanes]

Checked the cruise control and it did not work. Waiting for better weather to trace lines. How can the vacuum pump be checked? Just run engine and pull a tube off? Suggestions on where to get replacement tubing/hose?

 

[DavidC]

It may have just came off the pump. When I changed the oil pressure sensor I knocked mine off the pump, didn't notice till I had the ac on and air came out of the defrost, reconnected the hose and all is well,

 

[Chief USA]

My cat pulled the vacuum line off the pump trying to climb up into the engine compartment trying to keep warm. I could not figure out why my exhaust brake quite working. I kept checking along the lines and followed them back to the pump and there it was, pulled off the pump. It did not make any noise to draw my attention either.

 

[Bob4x4]

There is a 90 degree rubber fitting right at the cruise servo that cracks.Also if any recent work has been done under the hood a vacuum line may have been bumped and out of place.The mode actuator is just to the right of the acellerator pedal.You can apply vacuum to the actuator to verify it’s integrity(it defaults to defrost).

 

[Bill Lins]

There is a 90 degree rubber fitting right at the cruise servo that cracks.

Mine has dry-rotted almost to dust. Would you happen to have a part # & source for a replacement?

 

[petersonj]

How can the vacuum pump be checked? Just run engine and pull a tube off? Suggestions on where to get replacement tubing/hose?

If I were in your shoes and not knowing the history of the truck, I would get my hands on a hand operated vacuum pump with a gauge. This tool will make your job so much easier. They can be bought at Harbor Freight for less than $30.00 and are a useful tool for many other things as well.

With the hand operated vacuum pump you can check individual circuits and easily locate even the smallest leaks. And, you can perform the tests without listening to the clatter of your engine.

Your truck may have some or all of the following vacuum operated circuits: cruise control, HVAC system, transfer case, CAD (center axle disconnect on front axle).

I would start at the vacuum pump on the engine and just follow all of the lines to get a feel of the layout. Any lines or fittings can be purchased at any auto parts store. The parts will be generic, but it does not matter. You can repair and route your lines any way you wish. Small diameter plastic automotive grade lines or air lines will work for long runs.

Hope this helps,

- John

 

[RMHanes]

Rain finally stopped long enough to open the hood and see what could find. Saw that there was a loose and unconnected tube and that it had pulled out of the "coupling" at the pump. Jammed the tube back in and started up the truck. The "blend" door work will now cycle to all of the positions and is not stuck in the defrost positions. Thanks for all the replies!!! The coupling has cracks as Bill Lins mentioned. New search is to find a replacement for this 90 degree rubbed boot!

 

[KATOOM]

You dont need a specific 90* angle fitting but rather any vacuum hose fitting will work. Even a vacuum hose cut to make fittings will work. Just make sure all the rubber connections are in good condition. And glad you got it working too but for future reference if you ever run into this again, what you fixed was not the "blend door". The blend door controls the hot/cold selection and is electronically controlled. The vacuum pod "mode door" controls which vent the air comes from and there are two. One for panel/defrost and one for heat/defrost. There's also on for recirculation too but that only works on the max AC setting.