Heater Flap Stuck

[BAR]

The Heater SLide control for the passenger side it is Stuck in the 'cold' position.

I took off the underdash panel and tried to pull on the lever, but it is as stubborn as..

Anyone know of a way to get to the flap and move it, it may have gone 'over centre' or have some small obstruction.

Net result is that I don't have heating and of course we're in the middle of winter.

 

[John S]

The flaps on a 116 have "soft" hinges which generally needs replacing after 30 years, and replacing it is unfortunately a big job involving taking the dash out.

If you can reach the levers it may pay to try playing around with it and see if you can get lucky, otherwise have a chat to Styria or Mercules who have done this job before.

 

[WGB]

The flap hinges are made of foam and the foam disintegrates, the flap moves out of position and jams which jams the lever (s).

The biggest immediate problem is that if the heat levers cannot be pushed totally to the "off" position the heater valve will stay open which is not a great problem in winter but not much fun in summer.

1 - a quick fix is to remove the kick panel on the affected side(s) and loosen the 10mm nut on the aluminium extension at the bottom of the heater control on that side which becomes visible with the kickpanel removed. This effectively separates the vacuum control for the heater valve from the mechanical control for the flaps on that side and allows the heater lever to bottom and close the heater valve if necessary but you lose control of the flaps on that side,.


2 - The Bentley Technical Companion on Mercedes-Benz has an article which describes drilling a hole in the lower flap and attaching a small spring to hold the flap in the correct position so the flap will move and hopefully not jam. They say it takes 10 hours of time and it has taken me 2 years of repeatedly reading the article to understand how it works and I will try it on one or both of my cars at some stage in the future. Until then I have used No1 above as a reasonably simple fix in both my cars.

3 - Remove the entire HVAC system from the dash and either put in a new one (This is the old factory fix but you probably won't find a new one) or dismantle yours and either re-foam or find other hinge material.

Personally my first long term fix attempt will be the Bentley method now that I finally understand why it might work but if anyone has any better idea I'd be very interested.

Bill

 

[Styria]

Hi WGB and JohnS, it's the old bugbear that affects most 116's with the passing of time and deterioration of the foam that's stuck to the heater flaps by the company in the first place. Once the foam disappears, it allows the flap(s) to go over-centre and they will not close. I see it differently to both of you.

Whilst it may be easier, it is not necessary to remove the dash top, unless you want to remove the heater completely, but it is not necessary to get to the flaps.

Loosening the nut on the aluminium extension does not really achieve anything as the heater flap will still remain stuck in the open position. One might be lucky in freeing up the flap with some patience and jiggling, and it is then possible to adjust the opening action of the lever in such manner as to prevent the flap from reaching the "over-centre' position again. Again, I also fail to understand, Bill, how the small spring you are referring to is going to stop the problem occurring.. It really is a mechanical malfunction, rather than vacuum related. Maybe I am just a bit rusty on the subject matter...Regards Styria

 

[TJ 450]

AFAIK the spring serves to keep tension on the flap so that it doesn't return to the off-centre position.

Tim

 

[Styria]

AFAIK the spring serves to keep tension on the flap so that it doesn't return to the off-centre position.

Tim

Hi Tim, it is only the movement of the actuating lever that causes the flap to go to the 'over-centre' position - try as I might, I can't fathom how a spring would prevent the flap to reach that position...well, maybe yes but I really don't know...Regards Styria

Plus, I'd hate to be the one to fit a spring to that flap - how on earth would you get to it....

 

[WGB]

I have been staring at that Bentley article for 2 years and only recently worked out what it does.

It just forces the previously hinged edge to be pulled into contact with the part of the housing that it should have been hinged to by foam in the first place so that it is less likely to go overcentre and jam.

It still requires a lot of effort to get to it but it is only removal of the console not the dash.

I guess a workable answer to this conundrum will keep me busy for the next year or so now that I have fixed all the other malfunctions in my present system.

At least in the relatively mild climes of WA full heat is not really required - rather you need to be able to turn off the heat and use the A/C

Bill