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Blazer hvac issues

i have a 2003 chevy s10 blazer 4x4 with 72000 miles. im having trouble with air flow.sometimes the controls work properly in any position but sometimes the air only blows out through the front dash vents regardless of control position. i was told by a chevy mech. that atf from the transfer case gets sucked into system and causes control problems. he also said when this happens the hvac system only works through the floor and defroster vents regardless of control position. i’m hoping i just have a bad control valve not the atf issue. any help would be great. THANKS

My 2000 Blazer has three control valves for the HVAC; one to switch between floor and defrost, one to switch between the dash and the floor/defrost vents, and one for outside/recirc air.

A few weeks ago the floor/dash door got stuck in the defrost only position. The control valve is up in the dash between the steering wheel and the center console. I fished a coat hangar up through the floor vents and poked around until I had air flow through the dash and floor vents. A few days later the HVAC got stuck on dash vents only.

The dash control valve is accessible through the glove box. The actuator rod is visible in the upper left behind the glove box. On my truck the door seems to get stuck. Giving the rod a gentle push while switching to or from the dash vents popped it loose and got the controls working again. In hindsight I should have tried this on the floor/defrost control valve instead of using the coat hangar.

Ed B.

i’ll give it a try once it stops snowing around here.i’ll let you know how i made out. thanks for your help.

Just a quick note, to get to the defrost/floor control valve you will have to remove the black panel under the dash that goes from the steering wheel over to the center console. The panel is the with the two aux power sockets. If the control valve actuator rod does not move when the heater controls are switched, check the vacuum lines under the hood (driver’s side firewall).

Ed B.