heater A/C lever problem

[koan]

My driver's side heat control lever has a problem.

It used to operate over its full travel, then it started to jam at about 2/3rds up and needed some wiggling if moved past that point to return the lever to off, now it won't move much at all.

By disconnecting the mechanism I've traced it to the bottom mixing flap lever, it moves freely a few degrees (no pun intended) and feels and sounds like it's hitting something solid both ways.

What I should have checked is if the lever is stuck open or closed but didn't.

I've read the OZBENZ heater pts 1 and 2 but it doesn't feel like a warped flap as described there.

Is it possible that the flap has gone beyond it's normal travel and is now stuck behind some other part?

If a small object was to be lost down the demister vent could it find it's way to the bottom flap and interfere with its movement?

Would there be any way to remove the object?

I really don't want to take the heater box out...

koan

[koan]

It seems this is not a popular topic, I've worked out what's wrong so I'll reply to my own post, it might help someone with a stuck flap.

The flap sticks in the open position, poking a length of wire with a turned up end right into the middle of the box did something - not sure what, but the flap is free again.

I connected the levers and adjusted them, confidently moved the dash lever to hot and yes, it jammed again.

Not sure what the problem is but I can always free it with the wire, can't work out what I'm moving in there, could be the flap,  maybe some foregin object or it could be a divider in the heater box that has warped with heat.

Once the dash lever moves beyond operating the vacuum valve at the start a lot of slack appears in the lever mechanism, don't know how the dash lever connects to the flap levers but it's not direct. The slack amounts to about 1/5 of the total travel. It's this extra movement that allows the flap to move too far and jam.

A rubber band slipped over the flap lever to take up the slack  prevents the flap lever reaching the sticking point.

I'll organise a light spring instead of a rubber band.

I don't fancy removing the heater box to fix it properly, I've done it on a couple of cars, to replace heater core on one and evaporator on the other. It's an awful job, it seems like the whole car is built around it.

I hate working under the dash.

koan.

[s class]

koan,

I am watching your post with interest.  My 450SL has the exact same problem, and if anything I think its even worse to remove the heater box tha on the w116. 

PS I too detest working under/behind dashboards. 

Good luck

[koan]

thanks for detailed description of the job styria, i'm now quite sure the heater box won't be removed until absolutely necessary. if i ever need to replace the evaporator or core i'll do a proper, foam fix then.

for now i'll go with the spring or a fashion some sort of limiting stop. its what i would call a "dishonest" fix, does the job but hardly in the fine MB tradition.

(i've fixed the door trims by the way)

k

[koan]

well i thought i understood but not sure now...

i realise only the bottom part of the box, the flap section needs to come out but to get that out what do I need to remove?

not been into this area before.

i didn't consider the leaks around the flaps with my temporary fix, maybe I should do the job properly after all.

k