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SuperModerator
1986/1990 W126
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14,102 Posts
Discussion Starter #1
Just thought i'd throw this in, in case anyone was searching about a similar problem. It wasnt major, but my cabin temps often didnt seem to equal what the setting was on. It mostly seemed a bit feeble, but if so you could put up very high, next to or on the max setting, there was enough heat to be had. It always seemed a bit chilly on a longer trip, unless you whacked it right up. Then at some point it would be too warm. Apart from every now and then, when it got too hot without explanation anyway.
I changed my duovalve last year (i have the twin wheel climate version), so it wasnt that.
Wasnt too bothered since the heating did work, but just got back from a 600mile trip last night and thought i should sort it out since it didnt have the accuracy it should have done.
Suspected the cabin sensor so swapped it today. Extremely easy, and from a short trip across town today it seems to have done the trick. Got a longer trip tomorrow so that'll confirm it. If only all fixes were that easy..
 

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Premium Member
87 Euro500HVSEC. 88 Euro 560HVSEC. 89 Euro 560HVSEL
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4,278 Posts
Ian mines the same manual set as yours (twin wheel manual type with duovalve) and i dont get any heating at all. Where did you source your duovalve from as i suspect mines stuffed (havent pulled it apart yet). what did you pay for it?
I also dont get any cooling unless i hot wire the aircon clutch despite a re-gass, swapping out the temp regulator & klima relay, but thats another story which i suspect is electrical somewhere.
do you have a sunroof as i thought the cabin sensor is in the overhead switch panel.
 

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SuperModerator
1986/1990 W126
Joined
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14,102 Posts
Discussion Starter #3 (Edited)
Duovalve i had stashed away after i got it for 99p on ebay. Its extremely easy to check, i expect thats your problem so have a looky. Only 4 screws and an electrical connector, pull it out and check the diaphrams thoroughly for tears/rips. 5 or 10 mins. I believe you can buy the inserts from MB as opposed to the whole assembly. But i also heard you can get them from Bosch which is cheaper. Thats if you cant find good used.

Yup my sensor is clipped behind the grille located on the sunroof switch. That assembly pops out, levered out via the right hand side. Worth checking the sampler fan operation too by holding tissue over the end of the pipe when you have taken the sensor off the pipe. I knew the little fan worked but as it turned out the pipe wasnt connected very firmly so almost no suction either.
 
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