The International Cessna^® 170 Association

The stall warning horn is intermittant and only work nows because I have both VOR's out for repair and can tap on the unit to make it work. (That gets tricky on landing) I took it out and cleaned the posts and even took out the wing tab and sprayed it down with cleaner and checked it. I'm pretty sure it's in the horn itself, but I can't get into the unit itself. Has anyone ever taken one apart? I'd like to at least get in there and look around and see if there is a loose contact or something.

Thanks in advance!

v/r,
Jud

For some options - you can get a repalcement stall warning horn from Cessna for about $650, or you can go to Radio Shack and obtain an 85 dBa pizoelectric buzzer for $10 and have a backup when the cessna part is intermittant.

I just took mine apart about a month ago. there is nothing magic about them. Just start at the front and unscrew the knurled knob, which contains the light. I believe there is a nut you have to remove after that, and then you have to turn the the horn "screen" slightly so you can take it off. Then you can get to the rest of the parts. I actually took mine apart and put the horn under the panel and mounted the light itself on the panel just beside and above the control yoke, ( I put in a new center stack panel). The horn works great and the light is where I can see it. Good luck and have fun, like I said there is nothing difficult about taking the unit apart. Jon

The Buzzer and the Micro switch are priced so high, I still can't believe it. I do know that a Cheap back up alarm from Radio shack works great and fits right in.

The unit is accessed thru the front by removing the clip and light. Inside, you'll find a small metal "buzzer" that looks like a common device found in many old door alarms, etc. I repaired one once by replacing the capacitor that bridges the buzzer terminals with a similarly sized capacitor. (If the capacitor is failed insufficient "starting" current is available to excite the buzzer.)

This is an old thread, but the most common failure of the warning horn (other than a burned out bulb) is improper ground. The ground is found thru the wing-switch. The wing-switch is subject to water and corrosion and itself loses ground to the airframe. Cleaning up the wing-switch's contact-to-ground will fix 99% of stall warning problems. (An easy way to test if it's a wing-switch/ground failure is to clip a short jumper to the warning horn's wing-switch terminal and clip the other end of the jumper directly to ground. An easy way to test the entire wing-switch circuit is to ground the wire out at the switch directly to ground as it comes from the warning horn unit. With the Master ON, the horn/light should activate.)

Don't overlook the possibility of an open fuse/circuit breaker or loss of power to the warning horn unit.

Do not try to remove the original metal buzzer from the front of the unit. You must pull the whole unit out of your instrument panel and remove the screw from the back of the unit in the center. This will allow the buzzer to slide out of the unit. If any attempt was made of unthreading the buzzer from the front of the unit then you stand the chance of having the buzzer's lead wire short out on the opposite terminal. If that has happened and has ruined your buzzer then the $8 piezoelectric buzzer from Radio Shack will fit in there nicely wired in parallel with the light.