I have a 96 LT Blazer 4x4 that has heat is coming out of the defroster on the dash only. When I use the selector dial to change to any of the settings be it front vents or just the floor nothing changes the air flow. The A/C selection does not even work any more. The temperature control dial works just fine (from hot to cold) as well as the speed control/blower. I did check vacuum lines and replaced some right by the corner of the hood in around the vacuum ball.
I pulled the control panel inside next to the radio and could here air leaking in around the selector dial. I removed the hose coupling from that selector control and on the gray line I had a strong vacuum. I am not sure if this is normal to hear a slight hissing noise there or not when it is connected. May it be leaking the selector switch??

Any thoughts as to my problem would be greatly apprecited!!
I am not afraid to give to the GM garage when it is something I just can't fix on my own. But I hate the thought of something simple to replace or repair on my own if I can have some suggestions or causes to shot for on my own and possibly save some money in my pocket!!!!

Otherwise this has been a great running vehicle with 100k on it!!!
Minus basic maintenance/repair items...

Thanks!!

 

If you have a you-pull-it junkyard in your area, you could run over and quickly find the temp control for next to nothing. Would be an easy check before moving on to other things.


That's a vacuum diagram for a '95. I'm not sure if there is a difference, but I do not think there is. You could try to jump the vacuum source to the appropriate areas and see if everything is working properly. This would eliminate the switch and allow you to either definitively say it is the problem or rule it out.

Good luck!

 

I have the same issue in my '95. I have swtched out the heat selector and the vac hose out, but did nothing to fix the problem. I tested the vacuum at the ball under the hood and still has good vacuum. Could it be a stuck actuator? Does anyone have a diagram of where the locations of the actuators are under the dash and what vent they control? Thanks

 

THANKS KYLE!!! I tested the vacuums lines in the control area and they tested fine and opend the various control vent surfaces. Went to GM today and picked uptheNEW Control Panel for the interior. Cost me 60 bucks but it was the whole new panel right next to the radio. Swapped them out and it works just perfect!!! THANKS AGAIN for the diagram - got rid of the headache I had and I have everything working again!!

 

Glad I could help!

 

so I guess the electonic control for the temp switch went bad? Would be interesting to see how it Om-ed out due to there seems to be several who are doing all these Heater Cores thinking that is where their problem is. I have run into more then 10 of these that have the same issues, but can not come upon the test needed to check out the electronic switch for the temp selector. But seem to work fine when you change out this part.

Would help out many that have heater issues if the test procedure for this switch could be found and posted.

I have learned to keep some of these switches on hand to swap out first to see if its the switch over the heater core, but then again I have run into many that have the colored (not green) coolent. If its muddy, then they might have more problems then just a switch.

 

It would also be interesting to find out if the old controls have fluid in them, because there is a TSB on the HVAC controls malfunctioning when the vacuum switch on the transfer case fails allowing fluids to be sucked into the vacuum side of the controls...GM has a newer switch with a stronger seal to fix this problem.

 

My switch went bad on the transfer case (actuater switch) and my heater blows out heater,vent and floor and does not change when no mater where you put selector setting.Do you think it could be the selector switch?

 

Test it and see.

 

I also jumped the vacum behind the switch and it worked the vents so I guess I will go buy a switch also but the dealer here wants 95.00
Thanks for the help