Mooney 252 alarm buzzers connections

[goncaloareia]

Dear all,

My mooney 252 from 1988 is having its interior refurbished and for that ceiling plastic parts had to come off.

The maintenance shop doing the job messed up with the cable id's on the speaker/alarms connectors and now cannot find the correct settings to put everything working again.

They also tell me that the maintenance manuals are not precise on all cables for that area.

The problem that needs fixing is this: next to the speaker there is a bundle of 4 alarm horns/buzzers (some bigger than others) and the connections for all of them is a nightmare: they can get some of the alarms like the gear or stall to work but some just don't work...

Does anyone with a Mooney 252 or similar can get me some pictures of the connection/cable settings so that I can pass the info to the maintenance guys?

Thanks and best regards.

Goncalo Areia

Lisbon, Portugal

[kortopates]

The good news is that there are only two kinds of Sona alerts used, the SC628 continuous sounding unit and the SC628P pulse sounding unit. If memory serves me right, there is only one Pulse sounding unit which if for the gear - activated when the gear is still up at near idle MP settings. I recall all the other are continuous, including the one for your Autopilot that sounds the 5 beeps or so after you push the test button. The wires don't need to be hooked up to the same exact ones as long as the they are hooked up to the right type - continuous or pulse. A picture is not going to help, since I think they are all white wires. If you can verify you only have one Pulsing unit, then you need only isolate the gear horn wire to connect that one and all the others can be connected to continuous sonalerts. Its also easy to isolate the stall and A/P by activating them each individually, but you may find it challenging to isolate the gear horn without putting the plane on jacks and raising it. I only remember 3 right now in use, maybe your 4th sonalert is the second gear horn that activates when you move the gear from the down to up position without airspeed - but I was thinking there is only one for the gear so I am not sure about your 4th. The maintenance manual discusses how to test each of these - except the Autopilot one. You should verify all sonalert actually still works by applying 28v to them, if there is any uncertainty about them all working before your interior work began.

[goncaloareia]

Hi Paul,

Thanks A LOT for your help and tips!

The sonalert bundle on my ship has 2 SC628, 1 SC628D and 1 SC628P.

The maintenance guys were able to connect them but are not sure about the which wires go to each one.

A picture could help for 2 reasons I can foresee:

- there is a sort of a loop cable that goes from 1 sonealert to another, kind of giving this other one the power from the other. They are not understanding how to connect it and the manual (even the big electric schemes apparently don't give information on that) and from a picture of a similar installation we could understand it.

- the white wires that reach the area are all tagged with codes (like the rest of the cables in the ship), allowing easy identification of each one (that's something extraordinary that I always missed in the Piper Arrow I owned before the mooney...!!). A picture could allow us to understand this better.

I have a picture of the sonalert bundle.

Here's the link:

https://dl.dropbox.com/u/9286159/IMG_0797.jpg

Thanks again for all your help.

Goncalo Areia

Lisbon, Portugal

[kortopates]

Goncalo,
I don't believe the SC628D belongs there and suspect that was added by someone. There should be a logbook entry since this would have been a modification – if it was even a valid install. If its connected in parallel, that could kind of explain why you have 4 instead of 3 – someone added it to one of the 3 circuits without simply just replacing one. The SC628D has a tone of 1900 Hz rather than 2.9KHz. The big question is do you actually know of any valid audible alerts in your plane than the standard M20K: i) your Gear, ii)Stall and iii)Auto-pilot? If not, and you cannot find an explanation in your log book then I would simply discard the SC628D and make sure you Gear is wired to the Pulsing one, (SC628P) and the Stall horn and AP are wired to the one of the other continuous tone units. That is the standard Mooney configuration. There should be no concern for ensuring, for example the stall horn is reconnected to the exact same SC628 unit – it just doesn’t matter as long as the stall horn is connected to a working SC628. But if you actually know of a 4th audible alert in your plane, that would explain the SC628D.
Furthermore, I talked to a Mooney MSC IA here with over 20+ years experience and he has never seen a Mooney with 4 Sonalerts, further suggesting its highly unlikely that you actually need 4, but again a review of the log books should be helpful.
Since you probably would like to test the re-wiring for these, it would be very simple and convenient to just put the plane up on jacks (assuming they are readily available) to confirm you have the gear horn wired to the pulsing unit and eliminate any guessing from wire codes and schematic. It should be easier to find the hot wire for the gear when put on the master and raise the gear lever (w/ plane on jacks) than it may be to look up the wire numbers in the schematic. Same for determining the hot wire for the stall and AP test/disconnect function. But you should find the wire numbers for the Stall and Gear horn in the schematic if you want to look it up first; but probably not the AP since that was an option.
Good luck

[goncaloareia]

Hi Paul,

Thanks again!

The logbooks show nothing... and this ship had all the options for a 1988 M20K 252TSE, including altitude preselect, etc...

Is so far as non-normal items, I just found a stereo radio/cassette player (for aviation use) that was in the panel and removed and also a panel mounted co2 detector. Maybe this sonalert 628d was used for any of these (maybe the co2 detector)?

We'll use your valuable tips to sort this out!

Goncalo

[kortopates]

Goncalo,

The 4th Sonalert could be for the CO detector. I have a CO Guardian but I can tell you the CO Guardian does not use a Sonalert - it provides an aural tone directly into the Audio panel (if connected) as well as an internal buzzer plus an optional external panel light. Since its a possibility though, I would review the manufacturer's installation manual for your unit - its probably available on the web. If you can't find one, you could also press the test button sequence to see if that energizes one of the ciruits to the sonalerts - but its doubtful it relies on an external buzzer. Your previous stereo unit would not have used a Sonalert. But if there is an accessory still installed that was hooked up to your 4th Sonalert, activating its test mode should trigger the sonalert.

Please report back if you do find a legitimate use of the 4th Sonalert.h

[goncaloareia]

An update on this:

We finally found the reason for the 4th sonalert in the alarm cluster.

It's the preselect alarm from the KAS-297B module that our ship has connected to the KFC150 autopilot.

Thank you all for the tips and precious help!

Goncalo