Recalibrating HVAC

[Rocket Man]

I don't remember where I learned this but this has helped me and a few others when either the A/C or heat acts up, usually after either replacing the battery, an actuator, or HVAC control head. First, start the engine and turn all the controls to the off position, (rear controls too if they're acting up) , temp turned all the way down. Shut off the engine. Remove the positive battery terminal and leave it off for 10 minutes. When it's time to reconnect it, touch it to the negative battery terminal to make sure any residual electricity is discharged. Start the engine and DO NOT TOUCH THE HVAC CONTROLS FOR 5-10 MINUTES! The system will go through a calibration procedure, all the actuators ( mode, blend, recirc) will calibrate also. Then you can try out all the functions; heat, A/C, fan, etc and hopefully all will be working correctly. This also worked for my rear A/C when I pulled out the control head and reinstalled it a few days later only to find my rear A/C didn't work anymore.

 

[retiredsparky]

This is obvious but, sometimes folks who are not familiar with auto electrics read these postings...do not use any wire or metallic object to bridge between the positive and negative terminals of the battery or battery cables when they are connected to the battery. Bad bad things will happen (battery can explode, battery acid can burn your skin or eyes, sparks can burn your skin or eyes)!

 

[Rocket Man]

Good point; I should have said "touch the positive battery cable to the negative battery post but never bridge the battery terminals themselves or you will cause serious damage and/or injury". Thanks for pointing that out, Larry.

 

[R1_Demon]

Do you know if this process fixes the blinking AC (snowflake) and recirculation lights? I'm having this issue and cannot get this fixed for nothing. I did replace the battery 3 months ago but this issue was happening before changing the dying battery.

 

[Rocket Man]

Do you know if this process fixes the blinking AC (snowflake) and recirculation lights? I'm having this issue and cannot get this fixed for nothing. I did replace the battery 3 months ago but this issue was happening before changing the dying battery.

The blinking snowflake can be many things, it just means that something is keeping the A/C from turning on. If the controls are in the wrong position (A/C won't work if it's turned to defrost position, etc.) or if the compressor won't turn on for some reason like if it's too cold outside or the compressor is bad or you're low on freon. If your blend door is stuck in the wrong position the A/C won't work either so if the reset procedure fixes the position of your blend door and that was causing the problem, then yes it will fix the blinking. So it might fix your problem depending on what is causing the problem. Doesn't hurt to try.

 

[Bonestock]

By off position do you mean all the way left? The mode selector doesn't have an off in my 03. It defaults to defrost though so I'm assuming that's what I need to select it on

 

[Bonestock]

Didn't work for me

 

[Rocket Man]

By off position do you mean all the way left? The mode selector doesn't have an off in my 03. It defaults to defrost though so I'm assuming that's what I need to select it on

Fan off position. Mode selector straight up and temp straight up is what worked for me. I don't know if that matters but I know the fan needs to be off. This only works for recalibrating the mode, recirc and blend doors. If any of the actuators are bad it won't work. It's just meant for the times when the battery has been disconnected or you have replaced one or more of the controls and suddenly your system acts up.

 

[Bonestock]

Fan off position. Mode selector straight up and temp straight up is what worked for me. I don't know if that matters but I know the fan needs to be off. This only works for recalibrating the mode, recirc and blend doors. If any of the actuators are bad it won't work. It's just meant for the times when the battery has been disconnected or you have replaced one or more of the controls and suddenly your system acts up.

I'll try it again. I just find it hard to believe 4 actuators went bad at the same time or started working intermittently. I'm really suspect of of the HVAC head unit or brain but I can't find any info to check it or the actuators to confirm what's wrong. I'd rather not throw parts at it but that may be what happens or I just buy the service manual.