Air won't come out of vents - no detents when switching knob

digitalarchitect

New Member
Joined
Jul 5, 2018
Messages
8
Location
Salt Lake City
Hi all,

I've seen several threads in this forum related to the issue I'm having (the best one here).

In short, my A/C and heat selector knob isn't working consistently. Sometimes I'm able to switch the selection and it'll take (and I'll feel a detent as I move the knob) while other times it'll spin freely, possibly setting on defrost.

I've checked all my vacuum lines for leaks in the engine bay and I can't see anything. At one point in the summer the vacuum line leaving the engine block was unseated and after fixing it did seem to help...but not for long.

Any ideas on what it could be? There is a video below that shows the situation. Air will stop blowing all together if I move it from a working detent. Also, I hear a fizzle sometimes from behind the dash if it's on a working setting (like defrost) and move to another setting.

Thanks for all the help in advance. This one is a bear with winter here.

VIDEO: https://photos.app.goo.gl/MQfBN7B62rDFkMVN6

-digitalarchitect
 
When I had that issue, it turned out to be a stripped (read: cracked) plastic selector knob. Pull the knob straight out, it will be apparent if that is the problem. New knob, problem solved, if so.

On my same knob, the part of the knob on the back that is shaped to fit over the metal rod had cracked, and no longer would turn the rod. It acted just like the one in your video.
 
Last edited:
Looks like that could have been it! My previous vacuum line issues were a bit of a red herring for this - but sure enough when I pulled the knob off a piece was loose!

Thanks so much for the help @glwood ! Part already ordered on Amazon as a replacement.

Best,
digitalarchitect
 
Looks like that could have been it! My previous vacuum line issues were a bit of a red herring for this - but sure enough when I pulled the knob off a piece was loose!

Thanks so much for the help @glwood ! Part already ordered on Amazon as a replacement.

Best,
digitalarchitect
Like you, I thought my issue was vacuum line related, and I was dreading chasing that down also...I don't remember what made me look at the knob, but I believe another forum suggested that. Glad to help, and I hope this thread helps someone else also. Your video looked so much like what I was experiencing...

FYI, I found that knob at several local auto parts stores...
 
  • Like
Reactions: digitalarchitect
Good to know! - I'll run over to the stores when I have time. On Amazon it was only about $5 and will be here Thursday at least.
Link for anyone viewing this thread.

Picture of the broken knob as well.

IMG_20181218_134650.jpg
 
  • Like
Reactions: Chris
Thanks for sharing that link. Might be nice to have some of those laying around, just incase. Especially considering how cheap they are.
 
  • Like
Reactions: digitalarchitect