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Any climate control circuitry gurus?

2K views 5 replies 4 participants last post by  X2jay 
#1 ·
Hey guys, anyone here really knowledgeable on how the mk4 climate control unit works? I'm having some really strange circuitry problem, I can't seem to trace...

Our cars are old and so are the solder joints, I've been inside my climate control a few times in the past for an led conversion and some cold solder joint repairs. The problem could be from age, or something I screwed up, I'm expecting the later.

Basically whats happening is everything works perfect with the headlights off, soon as they go on and the illumination circuit goes on stuff starts acting up. A few of the buttons stop working, both the indicator light above the button and the function it activates. All the buttons themselves light up fine though.

Trying to find the problem I've been studying the TSRM, and it appears that it does NOT match the circuitry on my car WTF? Did they change it over the years, or is the wiring diagram just wrong? The pics from the wiring diagram, shown below, does not show the headlight illumination circuit being tied in with the climate control functions in any way.

In reality, at least on my car, the activation wire coming from the headlights (pin 8 on plug h12) is tied in with the transistors on the board. According to the wiring diagram they have no connection with pin 8, which is not even shown to begin with. I don't see anything in there that addresses the factory incandescent bulb circuit in the climate control.


 
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#2 ·
The electrical wiring manual shows diagrams divided up by function, not module. So the "illumination" stuff is all together on another page. You have to combine those pages in your mind to get a complete picture of the entire module's circuitry.

As far as what might be wrong, Stu is the resident HVAC control expert.
 
#3 ·
^^^ I searched the whole manual for anything related to it. The illumination section very lightly mentions it in one diagram, but it's missing too much information to be useful.

The indicator lights are designed to dim when the the headlights go on, with the use of the zener diode on the board, this much I know. I just need more info on where it ties into the headlight circuit.

hopefully Stu will chime in on this
 
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