wierd electrical issue

Here is a puzzling problem: my 2012 tacoma has a lighing issue. The HVAC panel is very dim. but still illuminates. It doesnt matter if i adjust the dimmer switch: all the other panels/radio work fine but the hvac doesn't. Any ideas?

 

Gremlins

 

Loose ground?

Have you done anything with wiring under the dash?

 

yes, i have done a bit of meddling.i tapped into the illumination circuit for the light for my 4runner 4wd switch- this is also dim now. I did that mod about 3 years ago and this is a recent change...but i am wondering why it is the power to the hvac control only

 

That sounds like it can be the cause but who knows why it took 3 years. I would just undo the tap to see what happens.

 

Since this just started - I'd suspect a ground is bad. If the lights are "two wire" (i.e. 1 power and 1 ground to item) the lights may be getting ground from the next closest ground point and the increased wire length may be causing a voltage drop. IF so try adding a couple ground wire/points near each lighted panel - shortest distance to a good chassis ground.

2nd is it possible you wired for the light you added is in "series" and not in a parallel connection?? This would dim the lights by dropping the voltage across each incorrectly wired bulb.

3rd You have a friend that is severely screwing with you.