W124 Heater Problem

roberto230

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Guys,

I would appreciate your help as I have now read advice and watched youtube videos for 2 days.
Finally took a deep breath and took the duovalue apart on the car today. Car is a W124 4 cylinder petrol 2.3 1992.
Problem is hot air on passenger side and cold on the driver's. When finally opened up I cleared out as much as appeared necessary on the bronze valves and the seatings - mainly dirty rad fluid no solid bits - put all back together and same problem still exists.

I would like to understand some things before looking at the heater matrix and possibly reverse flushing.

To assist me undertstanding videos and earlier comments on this site can someone please help by confirming (or otherwise):

1 Hot water should flow towards the duovalve from the matrix and return to the block via the small pump (having entered the matrix from a single pipe on the passenger (battery) side.
2. For hot air it is essential to have a closed valve as determined by the 26 degree setting on the internal consule.
3. Closed valve means the stem controlled by the solenoid is in it highest position i.e not depresses against the spring.
4. The valve nearest the driver side wing (RHD) controls the matrix providing heat to the driver side vents in the car. I assume this as the higher of the 2 hoses from the matrix as this is colder than the lower hose which is warm.

Prior to dismantling today - I have tested the electrical connections to the dualvalve and only get a multimeter measurement when temperature settings are in the cold position. When in the cold consule control position and with ignition turned on there is a jolt from both domes when the connector is put into it's correct position by connecting to the 3 pins.

I don't want to move on from eliminating a problem with the duovalve prematurely but would appreciate advice to make sure I have done as much as can be done before reverse flushing the matrix or looking at temperature sensors.

Thank you.
 

DREAMER NO2

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Did you check the auxhliary coolant pump is working this circulates the water around the system..I will look for a diagram of coolant circulation for you .
 

LostKiwi

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It won't be the pump or the matrix.
Since one port on the duovalve is cold and the other hot the issue is most likely with the duovalve or controller.
 

LostKiwi

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What about vacuum if the flap is shut it will stop all hot or cold air exiting in to passengers foot well or vise versa
From the OPs post he checked water temps at the duovalves. A cold valve inlet says no water flow=shut valve. Either the valve isn't being told to open or its failing to open when told. Only when you get hot water can you start looking at air.
 

DREAMER NO2

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Thinking if the auxhliary coolant pump is not working then it wont get full flow through heat exchanger ,, and only one half will get hot. There is a good post about this duo valve repair and is down the lower part of the forum in older posts .The poster is parrot of doom and the post is -- How To Duo Valve Maintenance interesting information ..
 

LostKiwi

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Thinking if the auxhliary coolant pump is not working then it wont get full flow through heat exchanger ,, and only one half will get hot. There is a good post about this duo valve repair and is down the lower part of the forum in older posts .The poster is parrot of doom and the post is -- How To Duo Valve Maintenance interesting information ..
Even without the pump it there will still be flow (my 210 has a failed pump and works fine - only way I found it was on a STAR diagnosis of the full vehicle).
 
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roberto230

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Thanks - I have seen PoD's posts and many others which are helpful but think this could be just one of the two values causing the problem.
Is it true to say that on a W124 the valve nearest the wing controls the flow through the matrix which results in heating the drivers side vents? Vents and fan are all working perfectly so no worries there also no Air Con on my car.

Big question - when current jolt is applied by solenoid to create magnetic field does that result in valve guider being pushed down (against the resistance of the spring) and prevent coolant from leaving the matrix - thereby causing air drawn through drivers vents to be unheated? If this is true am I understanding correctly that the value remaining in its rest position by the upward force of the spring would result in hot water flowing from the matrix and back to the block via the valve. Just trying to work all this out logically and get both valves working the same i.e hot.

Photos attached showing the duovalve - the "dome" on the inner (engine side) valve could not be removed unlike the one on the left of the picture (nearer the wing) and the guider was stiffer although I did release it and ressembled everything after wiping both "Chinese hats" and poking around in the dirty rad water for physical barriers.

Rob

20180114_152736.jpg 20180114_152730.jpg
 

DREAMER NO2

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You are right in how the valve operates . By removing the plug you should hear both click in and out .If you have one cold then it looks like the selanoid for that one as failed .Did you fit new parts inside ?.
 
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roberto230

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Thanks - no parts replaced yet just cleaned up and reassembled while I'm still trying to work out which valve is working. Both solenoids "click" when connector applied so it could be a physical obstruction such as a swollen washer that needs replacing if it is stopping the valve from lifting fully by spring action. Can you get washer kits in the UK for these or is it a DIY job (I have seen that video with 7/16th washers).
 
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roberto230

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Update

Took duovalve apart again and tested plungers - both go down when heater control set to cold and no obvious obstructions in areas full of coolant. Photo here of underside of plunger rods appear to show all seals intact and washers not swollen as to prevent plunger rods from moving freely. Have now removed the "umbrellas" from both sides of the duovalve and reassembled. On 10 mins idle running interior air seems warmer on the driver's side but not really very warm. Would the last thing to check be reverse flush the matrix or am I missing something more basic please??
 

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