Hello all!

I've been reading this forum for almost a month now and all the help I have needed for repairs has easily been found. Thanks to everyone who contributes all the great info!

I recently purchased a 1999 silver coupe and I've been working through all the small bugs to get her back to 100% functionality. Unfortunately I have hit a roadblock and need some help.

I replaced all the bulbs in the dual climate control unit so I know they are all functioning. Sucking the solder out was a load of fun! Anyway, unfortunately the lights still are not illuminating. The display works great and the stock LED button lights work. Just not the lights that tell me what button is where in the dark. I'm thinking power is not getting to the bulbs. What should I do next?

 

Not sure this will help... sounds like maybe you've already seen it?



https://www.corvetteforum.com/forums...splay-fix.html

 

Yes, I have read through that one. Post #18 shows what I have and like that picture all my bulbs light up with a battery. When I connect to the car the bulbs are not lighting up.

 

I've determined that I do not have power to the yellow wire in this picture (found in another thread) . They are splicing into it for radio back lighting so I assume this is my problem. Not sure sure what to do next. Any suggestions?

 

That Yellow wire is power for lighting. Remove that Gray wire.

If you need a source for the radio there is ALWAYS HOT and HOT with IGINTION ON that are in the passenger foot well you can use.

I have that info at home I can provide.


Mr. Sam

 

Thanks Chuck. That is the dimming control from the BCM landing on the Yellow wire at C16 on the HVAC module. Sounds like an internal HVAC issue from his soldering. I doubt the BCM suddenly went South.

OP, please explain this:

"I replaced all the bulbs in the dual climate control unit so I know they are all functioning. Sucking the solder out was a load of fun! Anyway, unfortunately the lights still are not illuminating. The display works great and the stock LED button lights work. Just not the lights that tell me what button is where in the dark."

You replaced all the bulbs and they are functioning but they don't illuminate?


Mr. Sam

 

Thanks for trying to help me with this guys.. Since I'm temporally buttoned back up I will borrow a pic from tstar's post (number 18 mentioned above). Like him I tested the lights with a 9 volt battery and all the lights come on just like his picture. I then decided to probe the yellow wire at connector that plugs into Hvac and confirmed no power when I adjust the dimmer. Lights at the cluster and radio are working fine.

 

That Yellow wire is powered by the BCM for auto dimming. Probably the BCM but you can check the wiring.

BCM Green connector C3 feeds it from B2 terminal pin. Here is the connector view.

https://www.dropbox.com/s/jg8zhlm8ph...Views.pdf?dl=0


Mr. Sam

 

Finally had a chance to check out the yellow wire at the BCM today. It appears B2 is not putting out any power. B1 only reads about . 25 volts, is this correct? Could I tap into B1 or B6 without causing any issues?

 

No, B1 and B6 actually are the way the BCM grounds other dimming light circuits. B2 is actually how the BCM provides power to the HVAC unit for dimming lighting. Just the opposite.

Normal light level is controlled by the IPC dimmer ****/potentiometer. Auto dimming is controlled from the serial bus to tell the HVAC unit internals to dim or go to OFF. I have worked on two cases where the HVAC would not auto dim and go OFF but just stay on. We had to put in replacements to solve that issue.


The HVAC control is unique in how the dimming lighting is powered and controlled.

It sounds like your BCM is the issue. Most likely a relay that a module shop could fix.

You can power the Yellow HVAC wire from a circuit that is HOT in ACC or ON. The HVAC lights would always be ON when the ignition is not OFF. A potentiometer/resistor could be installed to set the light less than full bright.

To do this you would use the Fuse 11 fed as shown below.


1997-2003

In the passenger foot well there should be 3 auxiliary power wires.

Orange wire taped off. Always powered from Fuse #7 (20 Amp). This Fuse is shared with the cigarette lighter.

Orange wire to a connector. Always powered from Fuse #1 (20 Amp). Fuse is shared with the accessory power port in the center console.

Yellow wire taped off. Powered from ignition switch when in "ACC or On". Powered from Fuse #11 (20 Amp). Not shared with anything.

Here is a link with more info and pictures:

http://www.digitalcorvettes.com/foru...ad.php?t=14632


If you have a 2004 there are no feeds but the same fuses can be used with Fuse Adapters to tap the power.


Hope this makes sense. Here is the Dimming Description from the FSM.

https://www.dropbox.com/s/m3nq3bvjz4...ption.pdf?dl=0

I have looked at all the dimming schematics and there is no way I see to use any other circuits to do what you need to duplicate the OEM design.

Let me know if you have any questions or need more info.


Mr. Sam

 

Thanks Mr Sam! I have hvac lights! I may add a pot if they seem to bright at night.

 

Wow, that was a quick fix. You must not be old and lazy like me. Uh, I mean busy.