Author Topic: 280SE jammed heater controls  (Read 4125 times)

powerglide

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280SE jammed heater controls
« on: 20 December 2012, 07:35 PM »
Can't move the heater control levers on my 1975 280SE. The heater is jammed 'on' which has been OK for the winter, but the other day when it got up over 30 deg I would have liked to turn it off.  The car had been standing for a long time when I bought it, and the cooling system looks like it needs an overhaul from top to bottom.  Possible the actual heater tap jammed in the 'on' position?  If so, where is it - I can't see it in the engine compartment.
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wacotech

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Re: 280SE jammed heater controls
« Reply #1 on: 21 December 2012, 12:46 PM »
Yes, got this problem too.
If you look on the sides of the heater box you will see the front levers control more than one lever on the side.
If you disconnect the levers you can sort out which one is stuck.
I managed to wiggle my stuck lever back into operation and then set the lever position so it didn't stick again but I could turn the heat off but couldn't get 100% full heat, but still enough even in sub zero temperatures.

There is a bit of info around on this subject if you search, but from i have read the jammed flap inside is because of a perished foam 'hinge'. To completely remedy the heater needs to come out and the hinges remade with new foam or other material - I was thinking a supple leather might be a good option.
1975 280SE W116.024/M110.983
D-Jetronic. 140,000km.

powerglide

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Re: 280SE jammed heater controls
« Reply #2 on: 21 December 2012, 03:22 PM »
Wizard, Wacotech! - could you do this through the fascia, or did you have to take out the console as well?
Powerglide

TJ 450

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Re: 280SE jammed heater controls
« Reply #3 on: 21 December 2012, 08:35 PM »
The 10mm nuts are accessable behind the knee bolster panel below the dash. You'll see them just to the left, and the right of the centre console.

The trick to get them moving again is to loosen the nut to allow movement, and this should allow the vacuum controls to work, but the flaps will still remain in their stuck positions. Fixing the flaps means a lot of work.

If you want a really quick fix in the meantime, you can simply disconnect the linkage to the vacuum pod on the heater tap and manually control the valve. That's what I have done.

Tim
1976 450SEL 6.9 1432
1969 300SEL 6.3 1394
2003 ML500

powerglide

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Re: 280SE jammed heater controls
« Reply #4 on: 26 December 2012, 07:21 PM »
Thanks again, Tim.  I followed your instructions with the 350SE and got all the issues fixed.  Apart from the problem mounting decent speakers properly, anything under-dash-in-console is a PITA.  I felt sure someone had encountered the same problem and had a fix.  Don't know what I'll do about it in the long term (if I get to keep the car).
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powerglide

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Re: 280SE jammed heater controls
« Reply #5 on: 28 December 2012, 04:41 AM »
It turns out to be a stuck heat control on the driver's side (right) only.  I find I cant get in to free up the jammed flap control.  Anyone suggest what needs to be removed to access it? Sorry to be so dumb about it.  It seems to be the heater box flap that's stuck - the other interconnected stuff seems to be OK. It is the unit closest the firewall that seems to be the problem, and I can't see how to get to it to free it up.
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wacotech

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Re: 280SE jammed heater controls
« Reply #6 on: 28 December 2012, 01:47 PM »
From what i gather reading around to renew the hinges requires taking the whole heater box out! & therefore most if not all of the dash - being full manual heating might be a bit easier. Good Luck. P.S. I have done mine yet so can't say from personal experience.
1975 280SE W116.024/M110.983
D-Jetronic. 140,000km.

powerglide

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Re: 280SE jammed heater controls
« Reply #7 on: 28 December 2012, 08:05 PM »
TJ,

It's the heater flap on the right side alone that is jammed - the control pivot moves freely.  Sorry to be dumb again, but where do I find the "the linkage to the vacuum pod on the heater tap and manually control the valve"?  I'll do that if I can ID the units you mention - I understand their functions from your description, I just don't know where to look for them.

The 10mm nuts are accessable behind the knee bolster panel below the dash. You'll see them just to the left, and the right of the centre console.

The trick to get them moving again is to loosen the nut to allow movement, and this should allow the vacuum controls to work, but the flaps will still remain in their stuck positions. Fixing the flaps means a lot of work.

If you want a really quick fix in the meantime, you can simply disconnect the linkage to the vacuum pod on the heater tap and manually control the valve. That's what I have done.

Tim
Powerglide

TJ 450

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Re: 280SE jammed heater controls
« Reply #8 on: 29 December 2012, 10:57 PM »
Powerglide,

I'll find some pics for you this evening.

Cheers,
Tim
1976 450SEL 6.9 1432
1969 300SEL 6.3 1394
2003 ML500

Tony66_au

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Re: 280SE jammed heater controls
« Reply #9 on: 30 December 2012, 03:09 AM »
I seem to remember the flap jams when the foam disintegrates and the flap closes just a little bit too far which jams the lever action and it needs to be pulled open a bit by hand to free up the mech and then re padded.

High density latex foam will do the trick but once again you have to get to it and pull it apart.

powerglide

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Re: 280SE jammed heater controls
« Reply #10 on: 10 January 2013, 08:40 PM »
Thanks Tim and Tony: the inability to close the heater control lever completely appears to be caused by the heater flap on the driver's side (R) being jammed open; this means the lever cannot activate the vacuum diaphragam that opens and closes the heater tap.  To fix the heater flap apparently means the  console and some of the dash stuff has to come out, so I'll do that later on when I need to pull the instrument panel (and find space to mount the Pioneer power amp).  Meantime, I have just tied the heater tap off with some wire - at least until summer is over.  It was one of you guys who provided that excellent illustrated guide to console removal, which enabled me to fix the 350SE console and under-dash problems.  Thanks once again.
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Tony66_au

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Re: 280SE jammed heater controls
« Reply #11 on: 12 January 2013, 05:31 AM »
Wasnt me with the Pics as I never documented the process.

Probably WGB or Tim

powerglide

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Re: 280SE jammed heater controls
« Reply #12 on: 21 January 2013, 11:45 AM »
'twas tim - but thanks 4 your comments also. Heater flap looks like a console + dash out job, and I may as well do both sides and replace the core while I'm at it.  so it's on the back burner while I get the simpler stuff done.  My W140 is making this look like a simple thing 2 fix. W140 has an ignition control box that works the same as a W126 controller, but, of course, it is different.  MB will supply a new one for a sqillion dollars, and one from a parted out car is the same age and about to die also (been thru that exercise).   I believe a bloke in the US rebuilds them for around a grand. So, the 280SE is looking more like a keeper than ever before, and the W140 is not, but I shed a tear because it is so lovely to drive and be in (when it's going, that is).  Just need to get a better sound system in the 280SE, acknowledging nothing will never be as good as the W140 Bose/Eurovox ethereal delight.
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powerglide

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Re: 280SE jammed heater controls
« Reply #13 on: 17 February 2013, 05:27 PM »
Chaps,

I am now planning the dash-out exercise to fix the heater box flap, and am thinking of all the other bugs I can maybe fix at the same time:

*Tacho is u/s
*a/c needs regassing (I read the somewhat daunting account posted last year with a shiver)
*install cuuise control - I can source a unit, but is it possible and is it complex to fit to a car that lacked it ex-factory?
*need to mount the power amp for the Pioneer somewhere
*need to fix that damn squeek/creak at the firewall when you turn the steering wheel.

The cooling system needs an overhaul (radiator, flush, hoses, clamps), so is it worth doing the heater core as well?

I don't want to get myself in a mess fixing things that aren't broken, but if I am going nto the trouble of pulling the console and the dash ... I would appreciate advice from someone who has done this.  All my 'advisors' tell me to forget this and get rid of the old Mercs and buy a Lexus, but you guys understand what it is about a W116 - you do, don't you?
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rob280sel

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Re: 280SE jammed heater controls
« Reply #14 on: 01 June 2013, 07:43 PM »
I did see somewhere there was a bloke that redid the foam on the mode doors without removing it!
Here is some info on foam on mode doors.
http://www.topklasse.net.au/forums/showthread.php?t=2737&highlight=heater
« Last Edit: 01 June 2013, 07:52 PM by rob280sel »