Heater plenum-box door is knocking

When I turn on or off the ignition on my '94 Chevy I have begun to hear a loud knocking sound that is comming from the air distributor box on the passenger's
side of the cab. The sound only lasts about ten or so seconds while the louver in the box is being sucked closed. Has anyone else had this problem? If so, what was the fix? Thanks,G-
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
There is a door actuator (motor) that the gears are stripped, when you shut the key off the motor is looking for home position. Enter the truck from the passenger door and look under the dash you will see the black box for the blower assembly, that is where the sound is coming from. Sorry I can't get more specific but it has been a couple of years since I last worked on a 94 with that problem so I can't remember how to describe for you where to look. I do know the actuator is a PITA to replace. It is about the size of a pack of smokes and I think it had three wires going to it.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

loud knocking sound that is comming from the air distributor box on the passenger's side of the cab. The sound only lasts about ten or so seconds while the louver in the box is being sucked closed. Has anyone else had this problem? If so, what was the fix? Thanks,G-
Live to learn with the noise! It's a huge PITA to get at and not worth the time. Mine's been doing it for YEARS.
Doc

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Live to learn... hehehe.... I do but I don't think thats what you mean?
-The Lonely Grease Monkey 1985' K5 305CUI TH700R4 NP208 KJ's successor
"Ignorance is preferable to error; and he is less remote from the truth who believes nothing, then he who believes what is a wrong." - Thomas Jefferson
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Hey guys, thanks for the advice. I ended up pricing the part #16141802 at the local Chevy dealer at $51.00 Ouch! So I did what I thought any tight as**d ba***d would do and I unpluged the dumb thing. Now when I turn the key I don't get any knocking. Of corse I also don't get hot air on the pasenger side floor. But that was the trade off for not being willing to spend the money on a new part. Thanks, Glen
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.