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Discussion Starter #1
96 Suburban

Everytime I turn the heater on or off, I get what sounds like a vacuumy hiss.

Are these things vacuum actuated?

If so, is the controller on its way out, or am I looking at replacing some lines?
 

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Commissioner Gordon
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5,139 Posts
No, it's all electric actuators, unless you have some type of aftermarket HVAC system.
The hiss could be some sort of ac noise while your turning on and off the systems (defrost). Not uncommon for the control head to get screwy, so keep an eye on things working and not working when you want them to, at times.
 

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Discussion Starter #3
everything works fine, but there's just this hiss. It's intermittant while just driving, but it happens about 95% of the time when I flip the fan switch from OFF to On and back.

And thanks for the good news about no vacuum lines. :D
 

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Commissioner Gordon
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If you've got a few minutes, pull the blowermotor out and check for leaves or other objects in there, it also gives you a chance to clean out the evaporator case too.
 
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