Any temporary fix for footwell heat?

My 79 300SD/116 (almost always) has no heat to the footwells regardless of which button is pushed on the climate control panel. The car holds vacuum well (for days!), so I think a vac-operated airflow routing door is sticking or something. Is there an easy way to rig something that would allow heat to enter the footwells? I suspect there's a way I could just work the door(s) by hand and free it up, but I have no idea where to look! As a matter of fact, I can't even figure out where the footwell airflow is supposed to come out!

The aforementioned (previous post) gal-pal is complaining- and hot air blasting on her face and torso from the windshield and dash vents is not helping. I used to be able to close the center and side dash vents with the levers and squeeze some heat out below, but no more! There is plenty of warm air in the plenum, and the blower works fine, air just won't come out down low. A full repair will eventually happen, what I need now is some info on how to access those doors and/or their actuators/linkage for a little manual "persuasion".

This is a classy beater, not a restoration project. Crude temporary fixes are welcome...

Thanks in advance, Dave Larson

[leathermang]

Dave,1. Trade the aforementioned Gal-Pal in on one that is not so demanding. 2. Keep the passenger side window down about 2 inches no matter what the weather.... that will keep her face cooler. 3. Wait till someone with some good suggestions posts before doing anything drastic. Greg

[dieseldaddy]

Well, this is what worked for me in my 1981 300tdt.

I am assuming that the vacuum systems for the heat are very similar in our cars...but I may be wrong.

I spent much of the afternoon with my goal to find and repair any and all leaks in my vacuum system. Turns out I may need much of the summer to hunt everything down!
However, I fixed my lack of footwell heat problem!

I removed both drivers and passenger side below-dash panels.
Then I turned on the heat to high. Noticed that the vent flaps were all the way up...as if the defrost were on.
I pushed the button next to defrost so that I could at least see what it did to the vents if anything and got nothing. I stuck my hand up there and manually assisted the vents down. Only took a little push to the back of it and down they s-l-o-w-l-y came.
But it DID come down and I had heat pouring out of there. (hold on, not done yet!)

THEN, I pushed the defrost button and they went back up...slow.
Good, I thought and pushed the button next to the defrost again, and NOTHING! bummer.

Dehind the center console just behind the footwell vent opening on the drivers side is the vacuum pump (I am assuming that is what it is) for those vents.
I wiggled the vac. line at the rubber connector and BOOM! down the vents came, much quicker than the first time. I repeated the defrost, vents go up, but then again they stuck and would not come down on their own. I WAS GETTING CLOSER!!!

SO, by process of elimination I replaced the rubber connection to the pump on the drivers side with a 2" piece of rubber tubing...
(drum roll please!)

NOW I HAVE FOOTWELL HEAT!!!!!!!

Consistant and QUICK. It appears that there was some kind of restriction in the original rubber connection, that may or may-not have been there for a reason, as I could not blow thru the original tube. No adverse effects can be seen so far by replacing it with a hollow one. Only good things like FOOTWELL HEAT!
(Even turns off and on automatically based on temp of air coming out!)

Sorry for the long post, but I am very excited to have that problem fixed.

Now onto the locks and hard shifting...

[surfblau]

I have noticed that pushing the 2nd and 4th buttons on the heater control at the same time will give me foot ventilation when no other button by itself will direct air to the foot well.

maybe a couple of months late....

[deluvak]

I had the same problem in my '85 300D. Everything worked fine except for the lack of footwell heat. I thought I had traced the problem down to an obstruction in the rubber tubing connecting the plastic vacuum line to the vacuum diaphragm unit which moves the footwell flaps. For some reason this rubber tubing was plugged with a small dowel, thus restricting the vacuum. Unfortunately, removing the dowel did not help (though it certainly had to be removed anyway). It turned out that the switchover valve affecting vacuum to that line was not functioning. Replacing that valve along with unplugging the line got the footwell flaps working perfectly.

Obviously check the easiest thing first which would be the vacuum diaphragm unit to make sure that functions properly. Then check the vacuum line to that unit. If those check out okay, then I would check the switchover valve. In my car there is a row of five of these valves behind the pushbutton ACC unit in the center dash console. You'll have to find which one of the valves goes to the footwell. I think mine was the 2nd from the left, but I don't know which it would be in your car. Hopefully, it'll just be a bad piece of rubber tubing.

Good luck,
Dan

[domchang]

bought a wind deflector unit and tried it out today, and what had been a suspicion before was now firmly confirmed. There's some source of heat on both the driver's and passenger's footwells with the heat turned off!

I left the car running when I got home from the test drive and felt around the footwell but could not feel any streams of warm air coming into the footwell.

It just felt like it was oozing in from the engine compartment/firewall area.

I tested it with the heater on and sure enough I could feel heat streaming in as expected.

Any ideas on where to look for this source of heat when the heater is off? Or is it just normal engine heat oozing into the driver compartment?