1986 HVAC control lights help

[kwest3904@gmail.com]

Mine functions correctly but lights don’t work. Checked and bulbs are good - ran 12 volts to them. In the three plugs which connect to back of controller, which supply + / - when headlights are on?

None of schematics I’ve found show plus my ability to read schematics is close to zero

Thanks

[Tom]

Mine functions correctly but lights don’t work. Checked and bulbs are good - ran 12 volts to them. In the three plugs which connect to back of controller, which supply + / - when headlights are on?

None of schematics I’ve found show plus my ability to read schematics is close to zero

Thanks

I'll look it up for you later this afternoon. Are any of the other dash lights not working when you turn on the headlights?

[kwest3904@gmail.com]

Thanks
Did some more checking

Oddly, the lights for AC, defrost and recirc work when depress them. They have two bulbs each, guessing one for if engaged and other illumination when headlights on

None of lights come on in HVAC controller (key on or off) when turn headlights on

All HVAC controls work as they should

Checked all fuses

[Tom]

The lights for the buttons seem to have their own power, so I'm guessing they don't dim with the dash lights. I'm not seeing a dimmer input to the cc unit -- or at least I haven't found it yet in the schematic if it's documented. Has to be there since those lights do dim with the other dash light (right?)... I'll keep poking around...

[Tom]

It looks like 12v+ on B1 drives the lights. This is a picture with 12v positive on B1 and ground on B5. I still can't find a dimmer input. My car is on the lift, but I'm suddenly wondering it those lights don't actually dim with the instrument cluster lights? Anyone able to check?

IMG_9930.jpeg (1.58 MiB) Viewed 926 times

[kwest3904@gmail.com]

Why is bulb for fan speed knob not lit?

I don’t care about being able to dim.

I’ll apply 12v per your info and report back though wondering about fan knob bulb. Maybe your bulb is bad?

[Tom]

Turns out that bulb depends on a different ground. Here is it with C2 grounded...

IMG_9937.jpeg (317.92 KiB) Viewed 882 times

[kwest3904@gmail.com]

Thanks

Question
Does turning on headlights cause C2 to go to ground or other pin to output 12 volts?

Going to check outputs on connectors that plug into HVAC controller with multimeter with headlights on. If either no ground or no 12 volts (based on answer to Q above) I will splice in ground or 12 v. Granted this will make lights on whether headlights are on or not which is fine with me.

[Tom]

Thanks

Question
Does turning on headlights cause C2 to go to ground or other pin to output 12 volts?

Going to check outputs on connectors that plug into HVAC controller with multimeter with headlights on. If either no ground or no 12 volts (based on answer to Q above) I will splice in ground or 12 v. Granted this will make lights on whether headlights are on or not which is fine with me.

I have not tested to confirm, but have to believe B1 gets 12volts (maybe variable via dimmer) when you turn the headlights on. Will test when I have the chance.

[kwest3904@gmail.com]

[/quote]

I have not tested to confirm, but have to believe B1 gets 12volts (maybe variable via dimmer) when you turn the headlights on. Will test when I have the chance.
[/quote]

YOU ROCK TOM!