Heater control switch

Tiny
JOE THE MARINE
  • MEMBER
  • 2002 CHEVROLET BLAZER
  • 4.3L
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 170,000 MILES
When I turn on the select switch to have the blower blow heat to the bottom, which has a little man in the seat with the arrow pointing to the feet, blows heat to the top air vents and not the bottom. I checked in the glove box and all the vacuum lines are connected and pulled the whole switch out of the dash, and they are okay. Is there any way to find out "why" it is not blowing heat from the bottom and stop it from coming out the top vents? I don't know where to start on this problem, since winter is coming soon, like to get this fixed. Also, do you have a vacuum diagram of the vacuum lines that run to all these doors and vents? This would be very helpful. Thank you for all the help you can pass on to me, and God bless all of you on what you do. Hope to hear from you soon.
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Friday, September 13th, 2019 AT 9:00 AM

5 Replies

Tiny
ASEMASTER6371
  • EXPERT
Good afternoon,

Does it blow from the vents to your face?

It sounds like you have a vacuum supply issue to the control head. It will default to the defroster vents when there is not a vacuum.

Roy
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Friday, September 13th, 2019 AT 9:40 AM
Tiny
JOE THE MARINE
  • MEMBER
Thanks for the information. Yes it does blow in my face, all the top vent have the heat coming out, should I change the defroster switch or look for the vacuum leak under the passage side and driver side? This I need to find out before I get started. Thanks
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Friday, September 13th, 2019 AT 10:29 AM
Tiny
ASEMASTER6371
  • EXPERT
Can you hear a vacuum leak?

If it has defrost and vent, then good chance it is either the vacuum switch behind the control head or the vacuum motor on the heater case.

Roy
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Friday, September 13th, 2019 AT 5:57 PM
Tiny
JOE THE MARINE
  • MEMBER
Can you send me a diagram of this vacuum switch and where it is located, if you can? This is still driving me crazy. I even tried another A/C control module and it still does the same thing. So I will try what you said in this last answer. Thanks and God bless you for your help. Hope to hear from you soon.
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Tuesday, September 17th, 2019 AT 12:18 PM
Tiny
ASEMASTER6371
  • EXPERT
Did your replacement come with the new vacuum valve for the hoses? The diagram I sent you is what you need

Did you verify vacuum source from the engine to the left port in the diagram?

Roy
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Tuesday, September 17th, 2019 AT 12:34 PM

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