Dash lights do not dim

[Scrubulum]

There are hundreds of threads out there with "dash lights don't work (no light)" problems. This is not one of those.

'95 Talon TSI AWD
My dash lights are on all of the time. Dimmer does not function.
I have removed existing dimmer and replaced with dimmer from junkyard. No change. I have also tried to test dimmer to no avail.

Does anyone have a schematic on how the dimmer works or suggestions on how to fix said problem. It is not just a simple potentiometer. Any suggestions would be appreciated.
Thanks.

 

[luv2rallye]

Unplug the dimmer. If your dash lights remain on, then you have a short to ground on the black/yellow wire from the lights to the dimmer. If lights go off, plug dimmer back in. If lights now always on you have a bad dimmer. Note you may have gotten a bad one from junk yard (very common) or it blew when you plugged it in (bad wiring). The dimmer is actually a circuit board that pulses the black/yellow wire to ground (the black wire) even though it is often referred to in manuals as a rheostat (potentiometer) - that is a carry over from old days. It cannot be tested or fixed (just replaced). The green/white wire should be +12V, the black to ground (test this with ohmmeter with dimmer unplugged), and the black/yellow to one side of the lights. The other side of the lights is +12V (when headlight switch on of course).

 

[Scrubulum]

Thanks for the reply. That is exactly what I thought it was just wanted to get someone else's opinion without throwing any ideas out. I imagine that the previous owner just shorted it out to make them work after the dimmer went south. You should be able to ground the switch (black), and power the green with 12+, and measure the output on the yellow. If only I had an oscilloscope.
I'm changing the timing belt this weekend, then need to bleed the brakes (send me into a spin each time I hit them when slippery, great for winter ) Then I am going to fix the stupid dimmer as I hate it so bright all the time.

 

[luv2rallye]

You should be able to ground the switch (black), and power the green with 12+, and measure the output on the yellow. If only I had an oscilloscope.
... Then I am going to fix the stupid dimmer as I hate it so bright all the time.

You don't absolutely need an oscilloscope (unless you just have to see the pulses). A dc voltmeter reads an average so it should increase when dimmer is turned up due to more pulses/sec. (just like the light should get brighter). If all else fails you could always replace the dimmer with an old fashioned potentiometer. Just make sure it can handle the power.