Clicking noise from heater box

[Afireinside]

I have a 94 chevy truck and whenever you let go of the key or shut the truck off you get a loud quick clicking noise for about 10 seconds from the heater box inside the cab then it stops.It used to only do it every once in a while but know it happens all the time.All the heater and a.c stuff works.Any ideas?
Thanks

 

[4xcrazy]

My 94 half ton does the same thing, was told it's a common thing in that year or something, really hard to get at it too, tried, and gave up. Mine also does it when i switch the AC controls from normal to max setting too. Sounds like something tapping on the vent door or something.

Sorry i don't know what it is, but it would help if someone else on here knows to let us BOTH know

 

[justhorsinaround]

From what I understand a limiting switch isn't doin it's job so the motor runs making the little plastic gears skip. Ours did that as well.

We'd just turn it on and set it to the vent or the recirc, listen to the tick, tick, tick noise and then reach up under the dash to a 3 wire plug, pull it and then no noise. Just have to live with either fresh air or recirc all the time.

This is a band-aid and I have no idea how to really fix the problem.