Sonalert location

[Tommy]

Hi guys!

 

My stall warning only sounds intermittently and I thought I will replace Sonalert first before doing anything else. 

 

Just want to if it can be done easily and if so where does the sonalert physically located? Is it in the cabin speaker?

 

Cheers!

[Awful_Charlie]

Might help if you said what model you are working with. In a M20M, the sonalerts are next to the cabin speaker in the headlining, but they are nothing to do with the stall warner (and combined gear horn) that is down by the pilots feet

[Tommy]

Apology it's a 1981 M20J (Serial 24-1142)

 

Thanks!

[jrwilson]

Mine lives in the avionics panel, left side. Aft of the firewall.

[Tommy]

Bump

[Marauder]

Mine is a late F and has an identical interior to the early Js. Both Sonalerts for the gear and stall warning are located directly over my head on the headliner next to the speaker. Black round units about 1.5 inches or whatever centimeters in diameter.

Sent from my iPad using Tapatalk

[larryb]

In the 84, they are behind the speaker grill above the co-pilot. They do get intermittent, so it is smart to replace them first before spending a lot of time tracing wires. And, they are cheap!

 

Stall warning: SC628  continuous sounding unit
http://www.alliedelec.com/search/productdetail.aspx?SKU=70186814

 

Gear warning:  SC628P pulse sounding
http://www.alliedelec.com/search/productdetail.aspx?SKU=70186622

[Will.iam]

Reviving an old thread that just saved me troubleshooting the stall warning switch as my sonaralert is dead. Crazy thing is i was expecting a 628 for the stall horn and a 628P for the gear but i have 2 more sonar alerts one is another 628 but the 4th or last one is a 628 D. What does the D stand for?  Also i tested the sonar alerts with 2 9 volt batteries in series and the 628P does not pulse but gives a steady tone like the 628. Is that because the voltage is too low or a faulty sonaralert. Come to think of it i remember the throttle used to beep but now just gives a stead tone so maybe it’s time to replace that one too? But what are the other 2 sonar alerts for?

[carusoam]

while you wait…
A quick reference of the POH wiring diagram, may show what a third sonalert may be for…

1) Stall warning, steady tone…

2) Gear up, throttle out, beeping tone…

3) ?

I remember some Mooneys got three…

Newer Mooneys use plenty of sounds sent through the audio panel…

Best regards,

-a-

[MikeOH]

The SC628 is 2.9kHz continuous

The SC628D is 1.9kHz continuous

The SC628P is 2.9kHz pulsed.

See Mallory website: https://mspindy.com/products/audible-visual-products/industrial-panel-alarms/30mm-panel-alarms/

 

[PT20J]

King autopilots have a sonalert.

[Will.iam]

37 minutes ago, PT20J said:

King autopilots have a sonalert.

Ah that must be it. As I do have a kfc-150 autopilot. 
so 

1 stall warming

2 throttle beeping

3 gear warning?

4 kfc-150 autopilot

I am ordering 3 as only one tested consistently good.

thanks for the info. 
 

as an interesting side note with nothing connected to the stall warning leads but a volt meter I got very good reliable 24 volt reading. When I swapped the one known working sc628 into the stall warning leads the voltage would pretty consistently go to 9-12 volts but only sometimes get the 24 volts and get the full volume of the sonalert. I’m hoping a fresh new sonalert will be more consistent at getting the 24 volts.

[N201MKTurbo]

5 hours ago, Will.iam said:

Ah that must be it. As I do have a kfc-150 autopilot. 
so 

1 stall warming

2 throttle beeping

3 gear warning?

4 kfc-150 autopilot

I am ordering 3 as only one tested consistently good.

thanks for the info. 
 

as an interesting side note with nothing connected to the stall warning leads but a volt meter I got very good reliable 24 volt reading. When I swapped the one known working sc628 into the stall warning leads the voltage would pretty consistently go to 9-12 volts but only sometimes get the 24 volts and get the full volume of the sonalert. I’m hoping a fresh new sonalert will be more consistent at getting the 24 volts.

If you are seeing a low voltage at the Sonalert, it isn’t the Sonalert causing the problem. The Sonalert uses very little current, so if you are seeing a vow voltage at the Sonalert, there is a high resistance somewhere else. Most likely the stall switch.

[Will.iam]

7 hours ago, N201MKTurbo said:

If you are seeing a low voltage at the Sonalert, it isn’t the Sonalert causing the problem. The Sonalert uses very little current, so if you are seeing a vow voltage at the Sonalert, there is a high resistance somewhere else. Most likely the stall switch.

True except when i take out the sonalert i get the full voltage but that’s because there is no load on the lines. 

[N201MKTurbo]

1 hour ago, Will.iam said:

True except when i take out the sonalert i get the full voltage but that’s because there is no load on the lines. 

OK, so the sonalert draws 18ma at 28VDC. You can simulate the sonalert with a 1.5K 1W resistor. If you put the resistor in place of the sonalert and didn't see battery voltage, there is a high resistance somewhere else. 

Edited November 29, 2021 by N201MKTurbo

[Will.iam]

4 hours ago, N201MKTurbo said:

OK, so the sonalert draws 18ma at 28VDC. You can simulate the sonalert with a 1.5K 1W resistor. If you put the resistor in place of the sonalert and didn't see battery voltage, there is a high resistance somewhere else. 

That’s a good idea, but with sonalert being so inexpensive compared to other airplane parts I decided to replace all of them and keep the one working one as a spare for the future. Will know if the one working sonalert was within resistance spec when i put the new one in soon enough. 

[MikeOH]

4 minutes ago, Will.iam said:

That’s a good idea, but with sonalert being so inexpensive compared to other airplane parts I decided to replace all of them and keep the one working one as a spare for the future. Will know if the one working sonalert was within resistance spec when i put the new one in soon enough. 

My bet is that M201K Turbo is spot on: your problem is NOT the Sonalert.  Given your description of your own troubleshooting pretty much proves the problem is somewhere else in the circuit. The intermittent nature (per your description) strongly suggests an issue with the stall switch.  I'd start with contact cleaner into the stall switch.

[flyboy0681]

Just throwing this out there, when I disconnect the KAP 150, occasionally the Sonalert does not beep. Are failures typical of these units (after 40 years) or is it more likely something with the computer itself?

[MikeOH]

10 hours ago, flyboy0681 said:

Just throwing this out there, when I disconnect the KAP 150, occasionally the Sonalert does not beep. Are failures typical of these units (after 40 years) or is it more likely something with the computer itself?

I had similar intermittent issues with my stall warning Sonalert.  After I verified full voltage at the Sonalert with the stall switch activated I just went ahead and replaced it.  I haven't had a problem since (>3 years).

I'd shotgun the Sonalert before spending money on the AP.  It's like a $20 gamble from DigiKey.

[Will.iam]

On 11/29/2021 at 12:37 AM, Will.iam said:

Ah that must be it. As I do have a kfc-150 autopilot. 
so 

1 stall warming

2 throttle beeping

3 gear warning?

4 kfc-150 autopilot

I am ordering 3 as only one tested consistently good.

thanks for the info. 
 

as an interesting side note with nothing connected to the stall warning leads but a volt meter I got very good reliable 24 volt reading. When I swapped the one known working sc628 into the stall warning leads the voltage would pretty consistently go to 9-12 volts but only sometimes get the 24 volts and get the full volume of the sonalert. I’m hoping a fresh new sonalert will be more consistent at getting the 24 volts.

4th 1900hz sc628 D sonalert mystery solved, when i replaced it and turned on my avionics it toned and then went off i then set my Alt preselect to 1000ft above me and sure enough it toned again. I guess i had forgotten that i should get a beep when approaching 1000ft to level off and didn’t realize that had stopped working. 
the 628 P is gear

and 1 628 for stall the other 628 is for kfc-150 

[flyboy0681]

3 minutes ago, Will.iam said:

4th 1900hz sc628 D sonalert mystery solved, when i replaced it and turned on my avionics it toned and then went off i then set my Alt preselect to 1000ft above me and sure enough it toned again. I guess i had forgotten that i should get a beep when approaching 1000ft to level off and didn’t realize that had stopped working. 
the 628 P is gear

and 1 628 for stall the other 628 is for kfc-150 

Is the 628 a steady tone or beeps?

[Will.iam]

3 hours ago, flyboy0681 said:

Is the 628 a steady tone or beeps?

628 P beeps the 628 with no letter behind it is steady tone. The 628 P is no longer made and 628 PR replaces it. Cheaper too. 

[Charles K]

Just adding to the thread and provide a source document for the topic at hand, as I'm doing some trouble shooting.

Referencing the Mooney M20 Series Service and Maintenance Manual, Manual Number 106, REV. D 8/1/81, pg. 9-167.

If your looking for the SC628P it is still available from Mouser, I mention this because the dBA are different levels from a P and PR, reference below. They both still pulse "beep", just with a 12 dBA level (not that you maybe tell the difference).

 

[Tmack201]

I had interior redone 2 months ago. Now stall warning horn, gear horn and KFC test are all inop. Since they’ve failed simultaneously, I have my doubts that the individual horns are the culprits. Any thoughts on where to troubleshoot?

[EricJ]

16 minutes ago, Tmack201 said:

I had interior redone 2 months ago. Now stall warning horn, gear horn and KFC test are all inop. Since they’ve failed simultaneously, I have my doubts that the individual horns are the culprits. Any thoughts on where to troubleshoot?

If the interior was redone I'd check the area around the sonalerts.   If the insulation between the sonalerts and the roof sheet metal was comrpomised and the panel shifted they could all be shorting against the roof.   Just one possibility.