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Discussion Starter #1
02 base model wagon. The dimmer control next to the headlight switch only dims the HVAC and ESC/seat heater/etc lights. The instrument cluster and stereo stay full brightness.

Any thoughts on where to start? Bad headlight switch or dimmer control? Thanks.
 

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I would look at the wiring harness going to the dimmer control (as Tomvw mentioned) to see if the wiring has been messed with. Follow it as far as you can.

IIRC it will be wrapped with OEM tape or inside the black plastic accordion looking harness.

The only other thing I can think of is maybe one of the pins in the plug isn't making a good contact to the switch. I would inspect the pins clean with electronic contact cleaner and see if that fixes it. Other than that A new dimmer switch?
 

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My thoughts:
"creative wiring", or the two happened to go stupid. The dash-illumination wire doesn't actually power the cluster backlighting (and, IIRC, the radio, too) - it just tells the cluster "hey, there's this much voltage on the wire, set your lighting appropriately."

That one's easy enough to try - just remove the cluster and radio fuses (alternately, disconnect the battery), and reinstall. Check operation.
 

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Discussion Starter #6
Thanks for the suggestions, folks.

I've had the car for three years now and this problem just started a month ago, following the car sitting for two weeks.

The only wiring change I've made is to add a USB charging socket in the button blank below the passenger seat heater switch last year. I couldn't find any 12v switched power back there, so I spliced into the... illumination circuit.

I'll have to pop the dimmer switch out and see if there might be something melting.
 

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Why would you do such a thing?

Switched power is available at the 75X lug on the relay plate (ahead of the left lower dash panel.) 3, maybe 4 screws to access it.
 

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Discussion Starter #8
It was the only convenient switched 12v in that area, and this was a proof-of-concept that I haven't bothered to upgrade yet.

Appreciate the 75X suggestion; I'll pull things apart this weekend or the next and see what I can find out.
 
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