Auto HVAC issue

[dougger]

I have the Auto controls in my 05 Silverado and the blower just started acting up. I usually put it on Auto and Defrost and the led on the display goes all the way to high but the blower either blows on low or not at all. I have tried manually changing the speed and it does nothing. It just started doing this and I have also had it not be working and then all of the sudden it would start to blow. It has happened that when I leave in the morning for work it would be working, when I leave for lunch or after work it may not be working. It is just a 50/50 shot that it will work.

I know on my old 2000 silverado, I replaced a resister pack, just did not know if this on has the same thing since it is newer and has the Auto Controls.

Thank you.

[MT-2500]

Originally Posted by dougger

I have the Auto controls in my 05 Silverado and the blower just started acting up. I usually put it on Auto and Defrost and the led on the display goes all the way to high but the blower either blows on low or not at all. I have tried manually changing the speed and it does nothing. It just started doing this and I have also had it not be working and then all of the sudden it would start to blow. It has happened that when I leave in the morning for work it would be working, when I leave for lunch or after work it may not be working. It is just a 50/50 shot that it will work.

I know on my old 2000 silverado, I replaced a resister pack, just did not know if this on has the same thing since it is newer and has the Auto Controls.

Thank you.

First step is to get a HAVC capable scan tool and get any codes and test it with the scan tool.
The fan is controled with a PWM voltage that needs a lab scope too test.
Reg volt meter will not measure voltage to it.

[j cAT]

Originally Posted by dougger

I have the Auto controls in my 05 Silverado and the blower just started acting up. I usually put it on Auto and Defrost and the led on the display goes all the way to high but the blower either blows on low or not at all. I have tried manually changing the speed and it does nothing. It just started doing this and I have also had it not be working and then all of the sudden it would start to blow. It has happened that when I leave in the morning for work it would be working, when I leave for lunch or after work it may not be working. It is just a 50/50 shot that it will work.

I know on my old 2000 silverado, I replaced a resister pack, just did not know if this on has the same thing since it is newer and has the Auto Controls.

Thank you.

I have not seen this issue yet but it is reported that the connector to the blower gets burned up. this can explain the blower working at times.

remove blower and inspect. if its all good then disconnect the negative battery connection turn ignition key on for 15 min then see if it works. if not then it can very well be the HVAC computer control module.

to get this scan which is possible you would need to go to a dealership . [secret codes]