| If
the heat in your car is always on, or you have
intermittent heat then cool, or your air conditioner
does not cool, although it checks out fine, it
is time to check out the mono valve. Obviously
if hot water is flowing into the interior of the
car the air conditioning system will not function
properly or if the hot water flow is intermittent
the heater will not function correctly.
The
location of the valve varies but it usually
is located between the firewalls on most Mercedes.
Follow the heater hose from the engine towards
the car's interior and you will find it. It
is a small rectangular part with a heater hose
connected to it with an electrical connection.
What
usually goes wrong with the mono valve is the
diaphragm inside the valve tears resulting in
the inability of the climate control unit (push
buttons) to control the flow of hot coolant
into the car.
Some
mono valves can be rebuilt while others require
that the whole valve be replaced. The valves
that can be rebuilt are found on the 123
and 126 chassis.
Remove the 4 screws on the top of the mono valve
and slowly remove the top paying special attention
not to launch the little spring in there. Remove
the diaphragm and check for tears. Make sure
you spread it out so you can see if it is ripped
where it contacts the metal.
Either
replace the diaphragm or buy a new valve and
that intermittent heat, no cool, or all heat
problem will be repaired.
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