Centre consol Heater control removal 1989 250D

chopperman

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My heater does not work on drivers side ( heater solenoid clicking valve closed with 12Voltinput ):(

Passenger side fully on :Oops: taking 8.7 Volts unless earthed.

No night lighting on Auto shift lever and on drivers heater control.

I can`t see a sensible way of taking centre consol and heater panel out to check the heater reostats
 

brianbrian

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cockney in the West Country
Your Mercedes
w124 250D, SL129-deisel
Where the two large knobs one for fan speed one for where you want to direct heat or cold these knobs pull of they are quite tight I put rag or toilet paper in my pliers so I don't mark the knobs when you have pulled these knobs of you will see large nuts also where the wood covering curves under you will see two small philip screws. Hope this helps
 

television

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2002 SL500, 216 CL500, all fully loaded
There are no rheostats it is a pulsed voltage


Welcome to the forum
 

wireman

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nice 201 2.5D 1993 & very nice 129 SL500 1994
Pull the plug on the duovalve, if the heater gives out full heat to both sides its normal and your heater matrix is OK. If its still cold the matrix or duovalve are suspect, see parrot of dooms DIY duovalve entry.

The heater controls panel is electronic and contains a computing device which measures the signals from 3 sensors (one in the roof near the interior light and one in each air duct behind the control panel itself), it sends pulses of variable duration out to the duovalve to proportion the hot water flow into the matrix halves. An analogue volt meter connected to each half of the valve will show up the pulsing by flicking its needle, always on is cold, always off is hot, warm is a bit of each.
Take care not to short out any of the circuits connected to the controls since the grey smoke that comes out of abused semiconductors cannot be put back in and the heater controler is far from cheap.
Always switch off the ignition before you disconnect or connect any part of it.

The front panels lower screws are hidden on my car by the radio's front panel so that has to come out before the panel can be removed as brianbrian describes, the control electronics just lift out once the panel is off.
There are two big nuts around the spindles of the control knobs which need to be removed as well as the pair of screws

The gear indicator lamp is burried on the gear lever assy, on the lower left hand side of the black plastic box that carries the lever there is a push in lamp holder, just follow the pair of wires that seem to disapear downwards to the lever and pull it gently out.

To access the console there is one screw in the middle of the rear edge of the console cover, it hides beneath the mat on the bits and bats well of the centre console so lifting out the front edge of the mat is your first step followed by removing the screw and carefully (it can be a little tight on its edges) lifting the back end of the console cover up untill it comes out.

The lamps are both slide in wedge 5mm T1 1/2 types but be wary of their rating, too much on the heater knob will melt it, I recall the heater knob being 0.36W and the gear lever 1.2W. All the dash lighting is by this style of lamp.
I have replaced all the failed ones in mine with the lower rated 0.36W types from CPC (12v 0.3A stock no SC00352 £3.03 for ten) with there being sufficient illumination desipe the reduced power.
There are similar lamps in your face vents as well as the knobs, ash tray and gear selector.
 
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