Heater Ventilation Mode Control Assembly - Lighting

[Dhood]

Anybody have the backlighting on the pushbutton mode control go out? I took mine apart then it didn't light anymore, so I got another from the junkyard and it didn't light either. The buttons have a separate light that works when pushed, but the backlit icons, so you can see what you're going to push, don't light. These units have a clear plastic light distributor panel in them, but I couldn't see any source of light. The radio panel next to it is lighting up fine but I can see a bright light source in there. How to fix?? This car is lucky I like to fix things otherwise it would have been cannabalized years ago. They are getting hard to find at the junk yards.

[Dhood]

I hate to reply to my own post but I didn't give you all much time to respond. I took the module apart this morning and found four incandescent bulbs on the top green board. I don't know why they would all stop working at the same time unless connected in series. I couldn't figure out the circuit so will take the board to a local electronics store tomorrow and see if they have replacement bulbs and will keep you posted. Alternatively, if anyone has a known good spare board and wants to sell let me know!

[LMP]

Can you specify what year is your TS?

[Dhood]

Oops sorry, thought I posted 'em

94 3.8

Seems like there was a minor change to the unit for the 95's; they have a different part number.

The lights are in parallel so could something have surged and blown them all at the same time I didn't see a break in any of the traces and since the substitute unit also didn't work, it might be something further up in the circuit.

There is no information in the GM service manual so it might be I have to disassemble the whole unit and test every connection. I'm working on the spare that also didn't work.

Thanks for looking into this.

[LMP]

THis
www.avigex.ca/xport/interiorlightsdimming.jpg
is from the '93 shop manual...probably very indicative of your '94.
ALl panel lights are fed through a transistor and a 2.5 amp fuse.

[Dhood]

I'll give that a shot. Thanks for posting.

/Dan