hvac controls frozen? edit: NM. car decided to fix itself.

AZIROC · 12-10-2025, 09:16 PM

So admittedly its been a few months since ive driven the car (18 Zl1 with 12k miles). Went to take it out this afternoon and it acted like it didnt want to start. Tried it again and it fired right up.

While driving I wanted to turn the ac/fan speed down some and when I tried, none of the buttons did anything. Tried up/down for the fan speed. Power. Even tried turning the dials from cold to hot. Thats when i noticed not temperature was displayed. Got to where I was going and turned off the car. Left about 10 mins later and car fired right up but controls were the same none of the buttons did anything.

Anyone ever run into this??

Edit: Ok well I think the car was just upset with me for not driving it. I looked online and checked some fuses. Everything looked fine. Threw the battery charger on there and decided to turn it on again. this time everything worked. So idk. Ill probably go to Costco and see how old this battery is.

Gunkk · 12-11-2025, 10:31 AM

Probably just a glitch from being low voltage (low on charge). 6th gen Camaro "smart charging" systems often undercharge the battery and the overly conservative AGM protection logic will often prevent a proper recharge during normal driving. This then can cause the modules to throw false codes and/or misbehave. Been there done that and wasted money replacing my first (factory) battery because of it. Forum members have reported that driving in daytime with headlights manually on (or another high current accessory like the defroster or hvac blower) will keep the alternator/charging system in high volage mode the entire time, improving the charging rate.

If you see the glitch again, then my recommendation is this:

Disconnect the battery negative for 30 minutes and all the modules will reset.
When you reconnect, wait a minute for the car to wake up.
Turn on the car in service mode (hold start button down 5 seconds WITHOUT your foot on the brake pedal). The check engine light will be lit indicating service mode.
Wait another 30 seconds, then start the car normally with foot on brake.
Check engine light will turn off. But if you still see a check engine light AFTER the car starts, then one of the modules probably threw a false code. Clear codes, turn the car back off (key-off), and repeat the service-mode restart.

As a garage queen weekend show car owner I now keep a tender on the car almost all the time. I also preventatively use the same tender on all my cars. Doing so has avoided two premature battery replacements.

AZIROC · 12-11-2025, 12:04 PM

I know these cars get real finicky when the battery gets low so I figured this was it.

Funny thing is usually I have a battery tender on it but I put it on a different car for the last few months. Guess ill be picking up another 1.

12-10-2025, 09:16 PM	#1
AZIROC Drives: '86 IROC-Z '18 ZL1 Join Date: Jul 2019 Location: Arizona Posts: 862	hvac controls frozen? edit: NM. car decided to fix itself. So admittedly its been a few months since ive driven the car (18 Zl1 with 12k miles). Went to take it out this afternoon and it acted like it didnt want to start. Tried it again and it fired right up. While driving I wanted to turn the ac/fan speed down some and when I tried, none of the buttons did anything. Tried up/down for the fan speed. Power. Even tried turning the dials from cold to hot. Thats when i noticed not temperature was displayed. Got to where I was going and turned off the car. Left about 10 mins later and car fired right up but controls were the same none of the buttons did anything. Anyone ever run into this?? Edit: Ok well I think the car was just upset with me for not driving it. I looked online and checked some fuses. Everything looked fine. Threw the battery charger on there and decided to turn it on again. this time everything worked. So idk. Ill probably go to Costco and see how old this battery is. Last edited by AZIROC; 12-10-2025 at 09:47 PM.

12-11-2025, 10:31 AM	#2
Gunkk Thank you Al Oppenheiser! Drives: Red Hot A10 ZL1 Convertible Join Date: Jun 2017 Location: Sarasota, FL Posts: 5,156 View My Garage	Probably just a glitch from being low voltage (low on charge). 6th gen Camaro "smart charging" systems often undercharge the battery and the overly conservative AGM protection logic will often prevent a proper recharge during normal driving. This then can cause the modules to throw false codes and/or misbehave. Been there done that and wasted money replacing my first (factory) battery because of it. Forum members have reported that driving in daytime with headlights manually on (or another high current accessory like the defroster or hvac blower) will keep the alternator/charging system in high volage mode the entire time, improving the charging rate. If you see the glitch again, then my recommendation is this: Disconnect the battery negative for 30 minutes and all the modules will reset. When you reconnect, wait a minute for the car to wake up. Turn on the car in service mode (hold start button down 5 seconds WITHOUT your foot on the brake pedal). The check engine light will be lit indicating service mode. Wait another 30 seconds, then start the car normally with foot on brake. Check engine light will turn off. But if you still see a check engine light AFTER the car starts, then one of the modules probably threw a false code. Clear codes, turn the car back off (key-off), and repeat the service-mode restart. As a garage queen weekend show car owner I now keep a tender on the car almost all the time. I also preventatively use the same tender on all my cars. Doing so has avoided two premature battery replacements.

12-11-2025, 12:04 PM	#3
AZIROC Drives: '86 IROC-Z '18 ZL1 Join Date: Jul 2019 Location: Arizona Posts: 862	I know these cars get real finicky when the battery gets low so I figured this was it. Funny thing is usually I have a battery tender on it but I put it on a different car for the last few months. Guess ill be picking up another 1.

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