I know there aren't many folk here who are familiar with the W140,
but I'm desperate.
The 1998 S420 has been acting strangely. Everything works in the
ACC, such as doors, fan speed, different modes, compressor, etc.,
but there is no temperature change in the cabin.
That is, if you want heat you get ambient temperature. If you want
AC, you get ambient temperature. If you set the temperature, the
fan and louvers all do their thing, that is, when it's trying to
heat the air is directed to the floor, If you put it on defrost it
blows on the windshield. If you have it on automatic the compressor
will come on and the proper vents will have air coming out of them
if you crank the temperature settings down. I also checked AC
pressures and temperatures and they're spot on. Duovalve works, is
not restricted, and the circulation pump runs and can be heard when
called on, as can the AC compressor.
The only thing I can figure is that there is a door of some kind on
the air distribution box that isn't letting air flow through it. I
checked the fresh air door in the cowl and it's opening and closing
as it's supposed to, and just to be sure I left the cover off the
cowl to see if that might be restricting air. Nope.
It's got me thoroughly stumped. No DTCs, either. It's like there
is no input from either the evaporator or heater cores and just
ambient air is blowing through the system.
Help?
Dan
Did this happen all at once, or was it intermittent/separate time for
heat/air cond.? Does it have a Klima relay?
Can you find a schematic?
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