i'm having a problem with the monovalve not receiving it's 12volts when it's supposed to resulting in hot air. I replaced the mono valve earlier thinking that it was the problem but on further investigation it doesn't receive 12 volts when the AC is enaged resulting in warm-cold mix of air coming from the center vents. I found a temporary fix to the problem is to bypass the wiring so that it continously receives 12volts and thus blows cold air only (of course, I would need to disconnect this for heat in the winter).

Seems as though my ACC switch control unit is the problem. Turning it on and off repeatedly I can get it to intermittently deliver the 12 volt current to the mono-valve and other times not.

Are the two other control modules under the glove compartmetn responsible in regulating the heating/cooling (i.e. supplying the current to the mono-valve?) I would like to restore the function of the ACC system (but at least for now, the 12-volt bypass seems to work). I want to make sure I'm replacing the right part, before spending the money on it.

any others with similar experiences?

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1) 84 300SD 285K+ Miles (Ver Calif)
2) 84 300SD 175K+ Miles (Ver Federal)