99 blazer 4x4 at I can select what vents work, floor, defrost, etc. The fan speed works. The recirc and outside air buttons do not. The light flashes 2x and goes out. Nothing but hot air full time. Also, on a possibly related issue, lights on 4x4 switch also just flash, but it sometimes goes into 4h, not 4l. I'm sure the blend door is screwed, but could it be something else? Thanks for any insight.

 

As I have told many, first thing I suggest with the 4x4 is to remove the 4x4 switch from the dash, carefully take the two halves apart to expose the printed circuit board, and then re-flow every solder connection. I found very little (if any) solder on the connector pins.

Did this to mine and now the 4x4 switches into 4H, 4LO and 2HI so fast I can hardly see the lites flash.

The HVAC problem is likely the vacuum connector/switch. Only cure I have read about is to replacement. But worth taking apart and having a "look-see" if there is something that can be done. I have heard about a small drop of light weight oil on the control hose ends to help them seal better....again worth a try.

Good luck.

 

OK thanks, I am off work all week so I will definitely try those ideas.