Gear and Stall horn issue

[kmyfm20s]

I have a problem for the great minds on this forum to help me solve!

I have a 99 Eagle and when I turned on the master switch this morning my stall horn was blaring. When I do my preflight I always check the stall vane for freedom of movement and I thought it might have stuck. I went and grab some contact cleaner out of the hangar, sprayed what I could generously and did the typical jiggle, tap, tap, etc. When I turned on the master switch again, no change, still blaring. I then pulled the Stall horn circuit breaker and no change. That made me scratch my head a little? So then I pulled the gear horn circuit breaker which is usually a beep, beep, beep not the steady horn that I was hearing and it went off. At this point both circuit breakers are out and no horn but if I pushed in either of the circuit breaker in individually the horn sounded and was constant, no beep, beep, beep. Both breakers needed to be pulled to keep the horn off. 

I have a MSC on the field and they have seen the problem a few times in the past but are too swamped at the moment to look up who’s planes they fixed the problem on and what the solution was. The avionics crew is going to look over the electrical schematics and do some preliminary diagnosis soon. The mechanics says is a Mooney thing. Tonight I plan on spraying all the contact switches related to the gear and the stall vane to see if it that is the problem. I’m hopping someone here would know what’s going on so I can fly my plane this Friday. 

Thanks! 

Karson

Edited March 21, 2018 by kmyfm20s

[kmyfm20s]

I will also add that I did check the emergency gear latch, it was secure.

[milotron]

I had this issue. After taking the switch apart and cleaning the hell out of it, the issue turned out to be one of the crimpon connectors was shorting to ground on the metal bracket around the stall switch. I presume it just bumped around enough to finally short out.

 

Don't overlook the simple and obvious...

iain

[milotron]

It looks like this in there. At least mine does.

 

iain

[kmyfm20s]

Quick reply, thank you! I hope it is that simple! I assumed it would be but you never know. My access panel is unfortunately riveted on behind the stall switch. I believe that where they placed the magnetometer for my G500.

[Marauder]

Quick reply, thank you! I hope it is that simple! I assumed it would be but you never know. My access panel is unfortunately riveted on behind the stall switch. I believe that where they placed the magnetometer for my G500.

Was the plane subject to heavy rain before this happened?


Sent from my iPad using Tapatalk Pro

[kmyfm20s]

 

30 minutes ago, Marauder said:

 

Was the plane subject to heavy rain before this happened?


Sent from my iPad using Tapatalk Pro

 

No but the plane had sat for a few months. This was the longest I have gone with out flying it and letting it sit. I did go around the pattern with it once just 2 days before. On that flight I did not touch the stall vane because I was just starting the engine to make sure the battery was charged and at the last minute decided to go around the pattern. My initial thought was the contact switch had a little corrosion and got stuck. I sent over a friend that is a mechanic to open the panel and check the switch with the above information. 

Edited March 21, 2018 by kmyfm20s

[kmyfm20s]

I still don’t understand why both the gear warning and stall warning circuit breakers would need to be pulled to silence the horn if it was just a the stall contact switch that was the problem. That would seem like a potential safety issue.

[carusoam]

Many have had difficulty with the stall switch...

But, the cross over of stall and gear warning sounds a little more unique.

The long bodies get electronic tones...

can you tell if it is a stall tone or a gear warning tone?

Someting odd is probably supplying the power.  Where it is being supplied may be determined by the tone...

the steady tone is the stall tone...

Got the wiring diagrams?  MM?

Midwest Mooney used to have the MM on their website.

PP thoughts,

-a-

[milotron]

18 minutes ago, kmyfm20s said:

I still don’t understand why both the gear warning and stall warning circuit breakers would need to be pulled to silence the horn if it was just a the stall contact switch that was the problem. That would seem like a potential safety issue.

I don't have a schematic for that model, but on my K, they are separate circuits, BUT since both of these are mission critical alerts, I would not be surprised if there was a diode or back feed intentionally in these circuits to back up the primary alert in case of a tripped circuit breaker or to alert you that that circuit breaker has popped.

 

iain

[ArtVandelay]

They are definitely different circuits on my 78J, the GW is a bit complicated, but the SW is dead simple.

But the later Js have both using same speaker?

[milotron]

The issue could be in the headliner where the two horns are located ( presumably ). As the stall switch is a the ground point, any spurious contact to ground on the appropriate horn terminals will cause this to happen also. My schematic shows several diodes at the gear horn ( as several things can sound it; gear speed switch, throttle switch, etc  ) then a short in just the right spot could cause this action.

Just postulating...I have had my own electrical demons to conquer today. Less costly fixing other people's problems!

 

iain

[M20S Driver]

3 hours ago, kmyfm20s said:

I still don’t understand why both the gear warning and stall warning circuit breakers would need to be pulled to silence the horn if it was just a the stall contact switch that was the problem. That would seem like a potential safety issue.

My Eagle is the same.  If I activate the stall horn, both gear and stall horn CBs have to be pulled to silent the stall horn.  

Question:  Does the stall horn stop if you turned off the audio panel?

[Piloto]

Karson I noticed that you mistaken the gear alert for the stall alert. I had the same problem and replaced the factory buzzers for a voice warning device.

http://www.aircraftspruce.com/catalog/avpages/voicegearalert.php?clickkey=2217090

The warnings are easy to understand since they come through the headsets.

José

[kmyfm20s]

We used @milotron approach and clean the hell out of the stall switch and it solved the propblem! It is still interesting that both circuit breakers needed to be pulled to silence the horn. Thank everyone for the help and input!