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HVAC lights stay on

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Old Dec 29, 2014 | 10:16 PM
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Default HVAC lights stay on

The HVAC lights on my 98 vette stay on after I park it after all the other lights shut off. I haven't seen how long it it is but I'll see if they are on tomorrow. The car is currently in my garage on a charger. Its a 98, the dual climate control. Haven't noticed it before and no codes in the HVAC? I searched and found one thread where they ended up replacing it and another one that said the condition just "went away".

Last edited by _Wayne_; Dec 29, 2014 at 10:21 PM.
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Old Dec 30, 2014 | 07:43 AM
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A friend had this EXACT some problem. All interior lights would go off except the dual control HVAC unit. I determined it had to be the actual HVAC unit was not acting on the request from the BCM to shutoff. We swapped in a spare I had and it fixed the problem. There are 3 circuit boards in there and I had no idea where to look to see if I could fix it. The old unit just sits on his shelf now.

That related Thread may have been us. Would like to know if it was someone else.

Here is how to access it for removal. Just takes about 20-30 minutes to get to it the first time. If you have a manual tranny you DO NOT have to remove the shifter **** and boot. Just release the shift boot from the console and rotate it and it will allow you to remove the console without removing the **** and boot.

This guidance goes beyond what you need to remove the HVAC unit so you can stop once the console bezel is removed.

http://www.vetteessentials.com/instr...zel_howto.html
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Old Dec 30, 2014 | 12:20 PM
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Originally Posted by dadaroo
A friend had this EXACT some problem. All interior lights would go off except the dual control HVAC unit. I determined it had to be the actual HVAC unit was not acting on the request from the BCM to shutoff. We swapped in a spare I had and it fixed the problem. There are 3 circuit boards in there and I had no idea where to look to see if I could fix it. The old unit just sits on his shelf now.

That related Thread may have been us. Would like to know if it was someone else.

Here is how to access it for removal. Just takes about 20-30 minutes to get to it the first time. If you have a manual tranny you DO NOT have to remove the shifter **** and boot. Just release the shift boot from the console and rotate it and it will allow you to remove the console without removing the **** and boot.

This guidance goes beyond what you need to remove the HVAC unit so you can stop once the console bezel is removed.

http://www.vetteessentials.com/instr...zel_howto.html
Thanks I think it was your thread I'm reading

https://www.corvetteforum.com/forums/c5-tech/3258476-climate-control-lights-staying-on.html

Okay I've got it out. The board with the lights looks good but ill double check do you think its something to do with the power supply board? I'll look at that tonight! Thanks for all the help
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Old Dec 31, 2014 | 07:48 AM
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The way I believe the dimming should work (via the FSM) is by the BCM varying the illumination voltage from 12 V to 0V. At least that is what the schematic indicates. You have to look at not only the HVAC connector pin out but also look into the Interior lighting volume. With that said, if the BCM varies the voltage then just changing my friends unit should not have fixed it. That is where the FSM again fails to fully explain how things actually work. As a result it must be related to the serial bus.

This is pin C16 which is fed from the BCM. Here is the connector in two parts. It could be the BCM but I hope not.







HVAC Connector Part 1






HVAC Connector Part 2

Last edited by dadaroo; Dec 31, 2014 at 07:52 AM.
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Old Jan 2, 2015 | 12:29 PM
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Thanks for all the great info! I'm going to take a look at it one more time but it would appear the bcm if fine (I actually have 2 so I swapped them and the same issue). I'm going to look at the HVAC controller closer and see if I can see a visible issue. It was working fine, noticed one of the leds I soldered on went out so i puller it out then re soldered it then I had the issue. So I probably messes it up some where. I'm suspecting I had the heat to high. Another interesting note is that after being on for a couple days the red leds are all good but the two blue ones I put in are out? Just an interesting observation
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Old May 27, 2015 | 04:21 PM
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Just in case anyone else is having this issue in the future, the power board in the HVAC unit was the culprit. I messed around with it, checked numerous solder joints and narrowed it down to the power board (the one without the lights, *****, screen, etc.). I was not able to fix my power board but I had an older HVAC unit that one of the dials wasn't working right. (another rare and un-explainable occurrence) swapped the power boards out and bingo! she worked.
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Old Jan 14, 2018 | 04:27 PM
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Default no lights at all FIX

What I found is the ribbon wire lost contact on the board connection, just use small screwdriver to push wires back into the receiver on the board.
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Old Jan 14, 2018 | 06:52 PM
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Moved to C5 Tech.
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Old Oct 21, 2025 | 06:51 AM
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Update on this - I ended up replacing the unit and all is well, never determined the actual fault but it was something in the HVAC control unit
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Old Oct 21, 2025 | 06:54 AM
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Originally Posted by _Wayne_
Update on this - I ended up replacing the unit and all is well, never determined the actual fault but it was something in the HVAC control unit
Wow...a 7 year update
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Old Oct 21, 2025 | 07:01 AM
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Originally Posted by lucky131969
Wow...a 7 year update

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Old Oct 21, 2025 | 08:04 AM
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Originally Posted by lucky131969
Wow...a 7 year update
All updates are good. Abandoned threads are a pox on us all.
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