Hear knocking noise coming from heater
October 30th, 2017, 4:19 PM
#1
Hear knocking noise coming from heater
Howdy All
When I turn my ignition switch to on while starting the engine I get a steady knocking noise coming from the heater motor area. It lasts for about 20 seconds and then stops. It also does this when I turn the engine off. Anyone know what is causing this? Thank you MC.
P.S. My truck is a 1991 2500 Silverado.
When I turn my ignition switch to on while starting the engine I get a steady knocking noise coming from the heater motor area. It lasts for about 20 seconds and then stops. It also does this when I turn the engine off. Anyone know what is causing this? Thank you MC.
P.S. My truck is a 1991 2500 Silverado.
Last edited by Montana Cowboy; October 30th, 2017 at 4:22 PM.
October 31st, 2017, 10:21 PM
#3
November 1st, 2017, 2:20 AM
#4
I looked through some old posts and it's actually the actuator for the fresh air door that causes the noise. It's really not hurting anything but if you hate the noise and want to replace it, just pull the glove box liner out and cycle the key. Should be easy to identify which actuator it is.
November 1st, 2017, 11:50 AM
#5
Thank you burnhedge I'll pull the liner out and see what I can find. Will get back and let everyone know what I find so others will know if they have this problem. MC
November 13th, 2017, 10:08 PM
#6
Howdy Folks
I fixed my problem by changing the Blend Door Actuator. It was a pain where it is located on the 1991 Chevy Silverado on the passenger side. After removing the glove box I could reach in with my left hand all the way to the firewall and then using a common screwdriver in my right hand to hold pressure against the 1/4 drive ratchet to hold it in place on the screw head while I repositioned my left hand to turn the ratchet to back the screw out. This wasn't done in one try because the socket would easily come off of the screw head because there just isn't any room to work plus having arthritis in both thumbs made it difficult. This was the upper screw that was difficult. The bottom screw is easier to remove.
I couldn't get the upper screw to back all the way out and what happened by accident was I broke the structure (actuator mounting hole housing ) on the actuator after which I was able to remove the upper screw pretty easy from underneath the dash..
The new BLEND DOOR ACTUATOR is centered such that it is located half way between open and closed. I tried to move ( gently) it to the full closed position so that it would fit on the " blend door shaft " but you are not able to move it by hand and I did not want to try and force it because that would damage the actuator.
The new BLEND DOOR ACTUATOR does not give instructions on how to clock the actuator to match the shaft on the blend door itself it just says " WARNING DO NOT apply power to the actuator until it is installed onto the blend door ". There are no instructions on how to do this and I didn't know that I could move the blend door ( I did not realize / see that the blend door could be moved by hand until I had bumped it with a screw driver by accident ) by hand to match the new actuator.
Now I know that you can move the blend door by hand to match the actuator position. I had no prior experience with these and again I did not realize that the blend door could be moved by hand until I bumped it with the screwdriver. I took a chance and hooked it up to the electrical connector and turned the key to the on position and this moved the actuator shaft to the correct position that matched the shaft on the blend door itself. I got lucky that I didn't over travel the actuator.
A CAUTION is required here, as soon as you turn the key to the on position power is applied to the actuator and it begins to move which brings up the CAUTION note provided by the manufacture. The manufacture of the actuator states that " IF ACTUATED PRIOR TO INSTALLATION ON THE BLEND DOOR, IT IS POSSIBLE TO ROTATE THE OUTPUT SHAFT BEYOND THE FULL HEAT OR FULL COLD POSITION. IF THE ACTUATOR ROTATES BEYOND THE FULL HEAT OR FULL COLD POSITION INDICATED BY THE ARROWS IT WILL NOT FUNCTION PROPERLY WHEN INSTALLED ON THE VEHICLE. So be careful when / if you apply power to position the output shaft on the actuator because as soon as power is applied the shaft will begin to move.
I installed the upper screw by gluing the screw to the socket( 7MM socket) and then used a short adapter that is 1/4 drive on one end and hex head on the other end. Once I got the screw positioned ( this took a numerous attempts to get the screw in the actuator housing hole) I was able to turn it as far as I could by hand and the used a small wrench on the short extension to turn the screw the rest of the way in.
Hope this makes sense to folks especially those who have to change one. MC
I fixed my problem by changing the Blend Door Actuator. It was a pain where it is located on the 1991 Chevy Silverado on the passenger side. After removing the glove box I could reach in with my left hand all the way to the firewall and then using a common screwdriver in my right hand to hold pressure against the 1/4 drive ratchet to hold it in place on the screw head while I repositioned my left hand to turn the ratchet to back the screw out. This wasn't done in one try because the socket would easily come off of the screw head because there just isn't any room to work plus having arthritis in both thumbs made it difficult. This was the upper screw that was difficult. The bottom screw is easier to remove.
I couldn't get the upper screw to back all the way out and what happened by accident was I broke the structure (actuator mounting hole housing ) on the actuator after which I was able to remove the upper screw pretty easy from underneath the dash..
The new BLEND DOOR ACTUATOR is centered such that it is located half way between open and closed. I tried to move ( gently) it to the full closed position so that it would fit on the " blend door shaft " but you are not able to move it by hand and I did not want to try and force it because that would damage the actuator.
The new BLEND DOOR ACTUATOR does not give instructions on how to clock the actuator to match the shaft on the blend door itself it just says " WARNING DO NOT apply power to the actuator until it is installed onto the blend door ". There are no instructions on how to do this and I didn't know that I could move the blend door ( I did not realize / see that the blend door could be moved by hand until I had bumped it with a screw driver by accident ) by hand to match the new actuator.
Now I know that you can move the blend door by hand to match the actuator position. I had no prior experience with these and again I did not realize that the blend door could be moved by hand until I bumped it with the screwdriver. I took a chance and hooked it up to the electrical connector and turned the key to the on position and this moved the actuator shaft to the correct position that matched the shaft on the blend door itself. I got lucky that I didn't over travel the actuator.
A CAUTION is required here, as soon as you turn the key to the on position power is applied to the actuator and it begins to move which brings up the CAUTION note provided by the manufacture. The manufacture of the actuator states that " IF ACTUATED PRIOR TO INSTALLATION ON THE BLEND DOOR, IT IS POSSIBLE TO ROTATE THE OUTPUT SHAFT BEYOND THE FULL HEAT OR FULL COLD POSITION. IF THE ACTUATOR ROTATES BEYOND THE FULL HEAT OR FULL COLD POSITION INDICATED BY THE ARROWS IT WILL NOT FUNCTION PROPERLY WHEN INSTALLED ON THE VEHICLE. So be careful when / if you apply power to position the output shaft on the actuator because as soon as power is applied the shaft will begin to move.
I installed the upper screw by gluing the screw to the socket( 7MM socket) and then used a short adapter that is 1/4 drive on one end and hex head on the other end. Once I got the screw positioned ( this took a numerous attempts to get the screw in the actuator housing hole) I was able to turn it as far as I could by hand and the used a small wrench on the short extension to turn the screw the rest of the way in.
Hope this makes sense to folks especially those who have to change one. MC
Last edited by Montana Cowboy; November 23rd, 2017 at 9:21 AM. Reason: To make more clear instructions.
November 29th, 2017, 10:16 AM
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Many complaints by chev owners listed on this forum....https://chevroletforum.com/forum/imp...95/#post348099
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January 10th, 2018, 5:42 PM
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Actuator working backwards?
I have a 1995 chevy silverado and the fresh air /recirculate actuator started making a noise so I changed it. When I installed it I had to take a screw driver and hold the flap open to line it up not thinking. Now I think it works bakwards, meaning when I have the recirculate button pushed in (on) the vent is closed. When it's not pushed in (off) the vent is open. I was even going to live with it even though it bothers me,but it seems that when I use the defrost it stays fogged up longer because the fresh air door is open to the cab air. Any help on how to get this corrected will be appreciated. I have had it off a few times a left the wiring connected and cycled it a little both directions and turned off. I even disconnected the battery thinking it would reset. Help please.
January 23rd, 2018, 1:45 PM
#10
I have a 1995 chevy silverado and the fresh air /recirculate actuator started making a noise so I changed it. When I installed it I had to take a screw driver and hold the flap open to line it up not thinking. Now I think it works bakwards, meaning when I have the recirculate button pushed in (on) the vent is closed. When it's not pushed in (off) the vent is open. I was even going to live with it even though it bothers me,but it seems that when I use the defrost it stays fogged up longer because the fresh air door is open to the cab air. Any help on how to get this corrected will be appreciated. I have had it off a few times a left the wiring connected and cycled it a little both directions and turned off. I even disconnected the battery thinking it would reset. Help please.
Did you fix your actuator problem yet? I'm thinking that maybe the new actuator is wired wrong inside since usually you can only hookup the connector one way and it should cycle to the open or closed position when commanded. If the old one opened and closed before like it should then I would suspect something is wrong with the new actuator. MC