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1986 HVAC control lights help
Posted: Sun Jan 21, 2024 3:10 pm
by 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
Re: 1986 HVAC control lights help
Posted: Sun Jan 21, 2024 3:26 pm
by Tom
kwest3904@gmail.com wrote: Sun Jan 21, 2024 3:10 pm
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?
Re: 1986 HVAC control lights help
Posted: Sun Jan 21, 2024 4:12 pm
by 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
Re: 1986 HVAC control lights help
Posted: Sun Jan 21, 2024 6:07 pm
by 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...
Re: 1986 HVAC control lights help
Posted: Sun Jan 21, 2024 7:17 pm
by 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 929 times
Re: 1986 HVAC control lights help
Posted: Mon Jan 22, 2024 4:35 am
by 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?
Re: 1986 HVAC control lights help
Posted: Mon Jan 22, 2024 8:24 pm
by Tom
Turns out that bulb depends on a different ground. Here is it with C2 grounded...
- IMG_9937.jpeg (317.92 KiB) Viewed 885 times
Re: 1986 HVAC control lights help
Posted: Tue Jan 23, 2024 4:38 am
by 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.
Re: 1986 HVAC control lights help
Posted: Tue Jan 23, 2024 8:11 am
by Tom
kwest3904@gmail.com wrote: Tue Jan 23, 2024 4:38 am
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.
Re: 1986 HVAC control lights help
Posted: Tue Jan 23, 2024 8:21 am
by 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!