No airflow from dashboard vents

[bobbennett33]

On Monday I bought a 99 C2500 with a 6.5L turbo diesel, 129K. It was a former fleet vehicle so it's basic (No power anything, 2WD, no A/C).

Yesterday morning I needed to use the windshield defogger and when I turned the selector knob I heard a some clunking from the dash area and airflow appeared at the windshield vents. Last night I moved the selector back to the dashboard setting and no air came out. I did not hear the clunking noises but I did get a whiff of a very acrid smell, presumably some type of electronics that control the air flow baffles burning. The smell lasted for several minutes and I verified that it was not coming from the engine compartment.

Any ideas here? I used the search function but could not find anything about this type of failure at TDP. From what I gathered on other boards there are a set of electronic actuators that move air-flow doors and some type of an airflow control module. Does anybody know more about these items?

Finally since this is a new-to-me truck, here's a list of what I plan to do within the next week or two, based largely on what I've read here:

1) oil and filter change
2) fuel filter change
3) PMD relocation (it was already mounted on a homemade aluminum block but it was not attached to anything at all, just held on by the wires!)
4) transmission oil and filter
5) add an OPS solenoid and check the lift pump

Anything else I should check?

Bob

[JTodd]

I had a similar situation and ended up taking the dash out, but I think it can be corrected without that. There is a set of flapper doors operated by a push/pull rod that you should be able to reach from under the dash just to the driver's side of center. The easiest thing is to have the key on and the fan speed switch turned to low, slowly cycle the selector switch from one position to another. I ended up just spraying some WD-40 on the pivot points for the flappers and helping them move until they moved by themselves.

To get a good look under there, you may want to take out the driver's seat and lay on the floor.

[bobbennett33]

Thanks Jeffery,
I looked under the dash and found the mechanical actuators that you mentioned. There was a spring-loaded slide for the dashboard flapper that seemed to be out of adjustment - I think the plastic ends that keep the spring captive were worn out. I tried to adjust the spring mechanism but this did not help. At last I tried a simple fix - I removed the spring and laid the two slides where the spring had been on top of each other and tie wrapped them together top and bottom and it now works flawlessly. Don't know about the longevity of this fix...

[Artworks]

You could have some 'junk' down in the vents , i.e. dirt, pens / pencils , 22 cal brass !!!!. These items will jamb up the flappers and stop them from diverting the air to the right places. you may have to take some of them apart to get at them. See how the 'duct work 'is routed and should just have to remove couple screws or clips. On my old 4 x 4 ( '1974, I cut a hole in behind the glove box to remove items that fell in and patched it back later ( duct tape !!! ) I diagnosed the same problem in an eary *** ORD , guy used it in field to shoot Gophers, vent was full of 22 cal. brass!!! he couln't get any heat, It went to garage few times, they couldn't fix it. He was goinh to get rid of car because of it , Till I told him what problem was LOL.

[quickv6]

Same issue with my truck. I notice that when on the dash vemts there is still too much air coming from the defrost opening. I looked under the dash played with the door it did help a little but did not fix the problem. I think something is broken or worn in the dash.