Greetings again gents.

After a recent jump start, the air in the truck, no matter what setting the control panel is set to, will blow hot air, then turn cold, then hot, and continue until I shut it off. (which never really stops all airflow, so no matter what hot air is entering the cabin every now and then)

The jump was because I left my truck for a week without operation, and had some electronics plugged into the cigarette plug without knowing it. The air will cycle hot/cold with engine on or off.

The control panel is supposedly one of those smart ones, with temperature numbers instead of just a blue/red bar, and an auto function which never really worked to begin with.

 

What year is your truck?

There may be a specific thread about the AC or Heater somewhere, run a quick search and see what it brings up.

 

The year is a 2000. I've searched quite extensively because I know this forum has lots of info, but none of the problems reported thus far was air changing hot to cold and cycling this over and over again.

 

Blend door. Do you have the automatic climate control?

You could try to reset the HVAC control head which will put the blend door through its cycle to determine the limits. THIS POST should help with that (actually pertains to your problem to the 'T').

 

Yeah that post is the exact same problem, with the automatic climate control. Figures... and I searched the forums for a good amount of time looking for the same post. Sorry guys. Admins can delete this one, I'll use the other post.

 

You can keep this one at this point. Doesn't really matter much.

 

Have you tried hitting the recirculate air or "Max" button with the fan off?

On some if the selector is on any position but Defrost or defrost/floor, the recirculate button, max button, will close the vent to the outside thereby stopping your airflow.

 

Yeah I used to do that to stop it, because it stopped it more than just having the fan in off, and the selector on the top vents. With this going full hot and cold though, I can steal feel heat coming through all the vents.

That used to drive me nuts when I first bought the blazer, no matter what the setting, you would always feel air coming through the vents, though in recirculate it wasn't as bad. I was told the auto environment control thing was a mess. Oh well. I'll be pulling the B+ as soon as I get out of bed to try and correct this.

 

I pulled the fuse, reset the system. The blend door is still cycling back and forth. Can anyone tell me how to jam the blend door to cold? Thanks!!

 

Kyle, just curious, I've read the post you directed to & it refers to the ""reset" method of removing the B+ power via fuse removal". Can you elaborate please? I take it it's referring to the dash fuse panel.

Just to confuse the issue, I see the US trucks have 2 fuses HVAC & HVAC1 (position 9 & 21 respectively). My truck - again to be different - only has the HVAC1 fuse (in position 21). 9 on my truck is ABS! LOL

Thanks