I have a 1999 chevy silverado and here is the problem that I am currently having. With the ignition key either on or off and with all heater controls either on or off, there is a noise that is rather loud and seems to be coming from the heating and ac duct on the passenger side of the truck near the floor board. It sounds similar to a motor running or a valve opening and closing continuously. All of my heating and ac controls work properly including air direction flow such as defroster, floor and mid direction, etc. What could this possibly be?
Thank you

 

Sorrry. This running noise stops when the ignition switch is turned of but remains at all other times ven with blower, AC and heat off. Kind of a loud buzzing. Thanks

 

Hi kybowtie1,

Welcome to the Chevy Forums.

Any possibility the serpentine belt's rubbing the fan shroud or something else? The belt tensioner could be shot, in which case you'll be certain real soon as it gets worse.

Is it louder when you pop the hood?

Or is it louder in the passenger compartment?

 

Thank you so much for taking an interest in my problem. This noise exist with the motor running or not running. It definetly isn't coming from the firewall out. The noise is always there (buzzing-running noise) with the switch key on but the motor doesn't have to be running. Lift the hood and you can barely hear it if the motor isn't running but get inside the truck and it seems to be inside the air duct on the passenger side. is there a mixer motor there maybe?
Thanks again

 

In my 94, there was a loud like tapping sound comimg from the passenger side. I figured out that it was the max door accuator. I'm not for sure if you have that or not on your truck.

 

You're probably right about the damper actuator. Stick your head down there and listen while you adjust the a/c settings from hot to cold and floor to dash.

I have one on a Tahoe with the auto a/c that constantly adjusts back and forth...the noise is just loud enough to be annoying.

 

Turn up the radio, ignorance is bliss. Most the stuff you worry about never happens, anyway.

Let's take a close look at this logically. Once you sit in your truck, you've got climate control,your own personal sound system, and cozy, padded seats; in essence, the most comfortable environment you'll be in all day.

Yet most people, instead of trying to prolong this obvious comfort, drive like they're seated on broken glass and have fleas nesting in their armpits.

Go figure.

 

my dads 92 chevy had a problem just like this.. but it was a tapping noise like the thing that tells the air where to go was flapping.. it stayed like this for over a year and then just stopped...and now his recirclation button or w/e that it doesnt work.

 

very helpful