Right floor heat OK, left floor none - PeachParts Mercedes-Benz Forum

Jim H · #1 12-05-2004, 04:44 PM

OK, I'm stumped.

1986 SDL

Center, outside and upper dash air vents work as they should. Passenger side floor heat vent works fine, warmed air blows from vents. Driver side floor heat vent does not work, no air.

AFAIK there is one vacuum actuator for floor air. If so, then it must be working, since I have at least passenger side air.

I wondered if there is a left/right flap linkage that's come loose? Nothing I've seen in the CD is clear on this. So, I spent some 'quality time' in the driveway this afternoon. I removed the left under dash panel, and the left and right side carpet from the center console.

The metal corrugated tube under the driver side dash for leg crash protection doubles as an air plenum. Holes/slots cut in the tube below the dash blow warm air downward. A a rubber connector at the outboard end mates with the door to allow air into the door. A piece that mates the air box to the tube.

I found shallow, hard plastic ductwork routes heated air from the box down below the driver and passenger seats to deliver heated air to the rear.

I even pulled the ashtray, radio and ACC panel to have a look-see.

I found all of this quite fascinating, but I found no visible external linkages, nor could I see a flapper, or damper, or anything to explain why right side works and left side doesn't. I'm not even sure I could identify the vacuum operator...

It was getting chilly in the driveway (barely 40, but no wind or rain

) and I decided to stop at that point. Even though I was curious, I didn't remove the glove box, nor the under dash panel from the passenger's side. AFAIK there is nothing there that operates the floor air...

So, what on/in the air box opens and closes to control left and right side floor air, and why would one side work and not the other?

Any help will be appreciated, photographs even more so.

For now, I'm planning to wear heavy socks for the winter.

Best Regards,
Jim

KCampbell · #2 12-05-2004, 04:55 PM

I had exactly the same problem, I "fixed" it but I have no idea how the linkages work.

I glued a plastic bottle cap on the bottom of the hot air chamber to prop the flap open that feeds the drivers feet area

Kevin

SD Blue · #3 12-05-2004, 06:19 PM

That's the problem, you're missing a plastic bottle cap.

(Sorry, after reading a few posts, I don't know what came over me.)

Jim H · #4 12-05-2004, 07:16 PM

Kevin,

It may come to some fix like that. As far as I went today, I couldn't even get to the flap or I would have propped it open, at least for the winter.

Warm socks will still work for now, and I'll keep searching the CD.

Jim

KCampbell · #5 12-05-2004, 08:31 PM

Jim

I should have provided more information, I hadn't realised you couldn't see the flap.

You have seen the plenum in the area above the drivers knees, have you removed it completely? Once it is out look at the area on the side of the tunnel where it mated with the heating boxwork, you'll see an fairly large opening. That opening has a flap that shuts off the air preventing it from flowing to the above-the-knees chamber. Once I had removed the aforementioned above the knees thing it was a pretty quick investigation which revealed the blowing-freely-in-the-breeze door. Since the door swings shut from the inside the pressure of the air kept it closed, and my feet cold.

Good luck.

Kevin

Jim H · #6 12-05-2004, 08:41 PM

Kevin,

Thanks for the reply.

No, I hadn't removed the plenum. I guess I can have another go at it, and this time remove the plenum/leg protector, and see what more I can see. I'll have to time it right for good weather (no snow or rain, and not too cold)

I'll also keep pursuing what's inside the box to see if it can be fixed.

Best Regards,
Jim

Jim H · #7 12-20-2004, 02:58 PM

Update:

Managed to do some troubleshooting.

The floor flaps are actuated by one vacuum actuator. It's getting full vacuum, and moves fine. The trouble is, only the right door is connected...

I did not remove the plenum, but was able to move some of the ducting aside, and could feel the door. It feels like there is no connection, it's just free swinging. I think the whole dash has to be removed to get at the box, and I'm not about to do that.

I found that a bent coathanger could be pushed up through a hole in the plenum, holding the door open.

The coathanger is not noticeable and will be a semi-permanent part of the car until warm weather, then I'll let the close for A/C season.

It's not the best fix, but it will work, and my toes will stop freezing.

Best Regards,
Jim

Habanero · #8 12-20-2004, 03:12 PM

I used a small piece of dowel with a string attached to prop mine open. Then when summer comes, just a quick pull of the string and it is out. Why are all mentions of this problem always with the driver side outlet? Is there that many more instances of problems with the driver's side, or do we just notice that and let our passengers deal with the right side problems?

tenknots · #9 12-20-2004, 03:15 PM

If it's like my 300SD, there is a fitting on the top of the flap that goes into where you can't see - that's connected to the actuator. The fitting (actually a piece of the door itself) is probably broken off, allowing it to swing shut - no heat.

Rreplace door (looks to be a *****) or get creative and find a way to keep it open.

KCampbell · #10 12-20-2004, 06:01 PM

This latest bit of info (that the part of the door to which the arm attaches may be broken) is quite welcome. I feel better about my "bodgit" repair knowing that doing something about it properly would be really difficult

Kevin

daverdla · #11 01-18-2005, 10:43 PM

Thanks - I guess I'm not a good searcher. I jam that flap open tomorrow.
Dave

mplafleur · #12 02-23-2005, 08:17 PM

I found the same thing today in one of my SD's. The flap for the right footwell opens fine, but the left just swings free. I did have to replace one of the diaphrams. It was the one for the footwell flaps too. It's the pod above and to the left of the glove box. Apparently, it controls the flaps for the left and right feet. Each flap is connected to a control rod via an arm where it exits the heater box.

I need to get a closer look at the that arm. I'm hoping that it is not part of the flap, but attached to the flap in a way that I can reattach it.

#13 02-23-2005, 08:42 PM

My SDL has done this since I bought it over a year ago. I have suffered through 2 winters because I haven't had the time nor the desire to contort myself into the foot well. I guess I'll tackle the problem soon, as my feet are freezing and my passengers always complain of being too hot.

I've noticed that the driver's side rear floor heat doesn't work either, but the passenger's side does.

mplafleur · #14 02-23-2005, 09:22 PM

Quote:

Originally Posted by VeeDubTDI

My SDL has done this since I bought it over a year ago. I have suffered through 2 winters because I haven't had the time nor the desire to contort myself into the foot well. I guess I'll tackle the problem soon, as my feet are freezing and my passengers always complain of being too hot.

I've noticed that the driver's side rear floor heat doesn't work either, but the passenger's side does.

The duct for the rear is AFTER the flap, so if you don't have foot heat up front, you won't have it in the back.

jim smarr · #15 01-08-2007, 07:37 PM

I have the same problem. Good vacum to control unit but it still does not
open door for driver side legroom heat. Wife screams about being to hot.
This is a 1989 300se with 337,000 miles. Guess it is time to replace actuator. It just does nothing with good vacum. One is on the way. I guess the diaphram is bad. Everything esle functions properly just drivers side leg room heat does not. It looks like it will be a serious undertaking.
Not much room to get to it.

Can't complain as this has been a good Benz.