How's everybody doing?

Lately I've experience problems with the climate control (control with wheel). At max heat max heat comes out. Turn down & max heat keeps coming out. Its either hot or cold, no in between. Yesterday I replaced the aux water pump - tested the old one & it would not work. Will I need to buy another climate control box, or can I take it apart and repair it? The heat control still does not work properly. Also, I let her run for a while and watched the temp gague & it went above the 10:00 mark, and continued to climb. I thought that after 90 degrees the aux water pump would pull water off the block to bring the temp back down. Winter is coming on, so, I guess I better get with it. Thanks for the help.

Hugh Sr.

1984 190d excellent condition 132,453

As for the "Hot, Cold, but no in between." There is a foam tube that comes from the vent in the top of the dash to the sensor behind the glove box, I bet that the tube has gone south and is your problem.

You can take the climate control box apart, and resolder broken connections on the board but it sounds like that tube is your problem and I'd try fixing that first.

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http://i106.photobucket.com/albums/m...73378_30-1.jpg

If I read your communique correctly,you BELIEVE the Aux Water pump has some
function involved in ENGINE Cooling?

Not Really,Or Indirectly...The Aux Water Pump's intended function is to deliver
HOT coolant to the Heater Core as regulated BY the Mono-Valve.They slapped
the Aux Water Pump in as an Engineering afterthought...
Not enough HOT coolant delivered to the HC at idle in some Northern Climes(Spelled EUROPE).

You may have a BAD Mono-Valve (I hope Not)
Or as Nick has suggested a fried trace or two on the CCU circuit board.

I would put a One Amp fuse in line on the power wire of the Aux Water Pump to
protect your VERY expensive CCU.(Elsewise If the Aux Pump LOCKS UP it draws TOO MUCH AMPERAGE and fries the CCU!)

I would also Fuse the Power wire to the Mono-Valve for exactly the same reason!
(Unlikely It'll draw the same way a motor would...But ,Better safe than sorry)

Crazy Me...I've also fused the Teeny,Tiny little Blower Motor on the W124 that
sucks Cabin Air across the Automatic Climate Control's Thermostat.(.25 AMP)
[The W124's CCU has an Automatic Electronic function that disengages from
potentially damaging circuits...so my fusing the three ACC sub-circuits is
overkill]

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'84 300SD sold
124.128

On your car (W201), I don't believe there is a monovalve, but I could be wrong there.

The tube and blower mentioned sucks a tiny amount of air over the temp sensor, which is located in the overhead console beside the dome-light. Blow the dust out, and see if the blower has enough suction to hold a small piece of tissue paper up. If not, the blower might have expired, it is behind the glovebox, remove the glovebox liner to access.

If the aux pump on the 201 stalls and shorts, it can take out the Climate Control Unit, the pushbutton unit in the dash. There will probably be a partially melted portion on the lower plastic cover of the CCU. Look for a used one, yours must come from a pre-'86 car (the one with the recirc button above IIRC).

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Gone to the dark side

- Jeff