Stall Horn

[Releew]

Stall horn was working fine and decided to stop.  

 

Does anyone have an exploded diagram view/schematic of how the switch and or entire circuit works?  Breaker is in and the metal tab is making contact at the bottom and top within the slide. What else is in the circuit?

 

Thanks,

 

Rick

[chrisk]

When my stall warning horn quit (sometimes), it turned out to be the sonalert.   http://www.alliedelec.com/mallory-sonalert-sc628/70186814/

[RobertGary1]

Yes, almost guaranteed to to be the sonalert. Inexpensive. My boat uses the exact same P/N sonalert.

 

-Robert

[DonMuncy]

If you haven't already, open the storm window, turn on the master, and move the stall warning vane. If the horn doesn't sound, it is either the switch itself (unlikely), the connections or wiring (a little unlikely), or the sonalert (most likely).

[RobertGary1]

If you wanted to be real sure, place the probes of your multi- meter at the sonalert while someone outside flips the tab and notice voltage applied when you do not hear the horn.

 

-Robert

[Releew]

Thanks!  Will put a meter on it tomorrow!

 

Rick

[MooneyBob]

.

[Releew]

Did you forget to type something?

[Releew]

It was the Micro-switch behind the vane.  Jump it and got the tone.

 

Thanks for everyone's input.       .

 

Rick

[DonMuncy]

I think someone has suggested that one can squirt contact cleaner in there, wiggle it a bunch and maybe get it to work again. I understand they are tough to remove and replace.

[Releew]

Don....

 

Thanks for the feedback!  Actually pretty easy. (for a change)  Inspection hatch is located right behind the entire mechanism.  Looks like a standard micro-switch.

 

Rick

[DonMuncy]

As usual, I'm talking when I should be listening.

[jetdriven]

Don....

 

Thanks for the feedback!  Actually pretty easy. (for a change)  Inspection hatch is located right behind the entire mechanism.  Looks like a standard micro-switch.

 

Rick

 

Its a standard micro switch but its inside a sealed up plastic casing that costs over a grand.

[Guest]

There is a Mooney conversion kit to replace the Safe Flight lift detector with a Mooney manufactured part using a standard micro switch.

Clarence

[RobertGary1]

Good fix! Always feels good to diagnose the problem yourself isn't it?

[Releew]

Yep.....  But this site, and well....most of the folks on here are very helpful.  Outside of this site, I do not see any good resources available to troubleshoot a problem.  If you call a shop they just want you to bring it in....obviously.  

 

I have a great AP/IA that works with me but he leaves it to me to do the research.  This site allows me to at least get basic feedback from folks who have in-depth experience, focused on this aircraft. That's the best possible path to identify and troubleshoot any problem......experience.

 

I've been flying for a while rentals and my own aircraft but having a Mooney is quite a different adventure!

 

Rick

[Brandontwalker]

Were you able to crack open the $1k plastic housing and replace the $5 switch inside?  I would be interested in the end result as I have the exact same project in front of me.

[mike28w]

 I'm one of those guys who sprayed some electronics grade contact cleaner on the switch from both sides and moved it up and down a bunch and sprayed again , multiple times.......That was about 8 years ago, haven't had a problem since.....   I bought the contact cleaner at radio shack for less than $10 bucks.....  ymmv !    

[Releew]

Inside was fine.....  Top hat was worn down!

 

Rick

[Woodpile]

Thanks for the entries on this topic. I'm a new 20F owner and the stall warning was not working. I sprayed the switch, no change. I taped the switch on, and when I put the multi-meter on it, there was a little noise. I thought it was continuity, but it grew louder the more I tapped it. I suspect the horn was dirty and worn. It takes a bit to get going now, but it works. Since there is not a lot of spare time in stalls, I am replacing it. The link above looks like the correct part, Mallory Sonalert SC628. Amazon will get it in the mail for $4 less.

Did I miss the thread on how to get that dang headliner out?

[N201MKTurbo]

Take out all the screws, undo all the wires, disassemble a couple of lights, nothing to it! 

When you put the sonalert back in make sure the terminals will not short on the roof.

[MikeOH]

Not saying this is without risk, but I did NOT completely take out my headliner on my M20F when replacing the SC628 stall Sonalert.  I removed enough of the screws such that the back of the plastic headliner dropped down; I then reached in, held the Sonalert with one hand, and unscrewed the retaining ring with the other.  The wires were long enough to move the Sonalert to where I could unscrew the terminals and install the new one.  Maybe a half hour total time 

[Woodpile]

Thanks, MikeOH - that is exactly what I ended up doing - with dozens of screws out, there was still some secret thing holding the front in anyway. I was well along on Turbo's path before I went that route.  When the new one arrives, I'll just take out those 3-4 back screws.

[N201MKTurbo]

3 minutes ago, Woodpile said:

Thanks, MikeOH - that is exactly what I ended up doing - with dozens of screws out, there was still some secret thing holding the front in anyway. I was well along on Turbo's path before I went that route.  When the new one arrives, I'll just take out those 3-4 back screws.

You didn't ask about changing the sonalert, you asked about removing the headliner 

I just removed mine to change out the coax to the comm antenna. I should have considered that you only wanted to change the sonalert. My bad.

I'm glad you got it done without much effort!

[Hank]

38 minutes ago, Woodpile said:

Thanks, MikeOH - that is exactly what I ended up doing - with dozens of screws out, there was still some secret thing holding the front in anyway. I was well along on Turbo's path before I went that route.  When the new one arrives, I'll just take out those 3-4 back screws.

The secret holding at the front is probably the visor attachments. Had to remove mine to get the headliner out.