96 gmc sonoma ac/heater controls do not work

1996 GMC SONOMA
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GMCSONOMA
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I have a 96 gmc sonoma with 189k miles, and the swith contorl for the heater and ac goes on but it only blows out of the defrosters and floorboards. both the heat and a/c work fine but the controls do not change where the vents blow out of. thanks for the help.
Jun 20, 2007 at 3:55 PM
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DANIMALGMC
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It sounds like you lost a vacuum hose under the dash somewhere. The vacuum controls the mechanism that controls the air flow selection.
You might be able to here the vacuum.
And if you;'re a smoker, blow smoke under the dash and follow it.
Or bad control valve
Jun 25, 2007 at 10:18 AM
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GMCSONOMA
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I'll try that, thanks for the help, I hope it works, its kind of annoying.
Jun 25, 2007 at 12:31 PM
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