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Annuciator lights test intermittent

rotorman

By rotorman
in Modern Mooney Discussion

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rotorman Community Regular

rotorman

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The engine was changed on the aircraft. Subsequently the annunciator lights test function is intermittent.  On initial start everything worked correctly. All the lights came on when the test button was pushed.  During the flight the test function did not work after multiple attempts. When pressed nothing came on. However the gear down light and ram air light worked when those services were activated.  After landing everything illuminated as it should when the test button was activated. So the test function is intermittent. The gear and ram air lights work as they should but do not test intermittently.  During the failure mode I know the vac hi/low light is not working because it should be on before engine start. I don't know if fuel or voltage lights work during this failure or they are just not working during test mode.

This sounds pretty confusing since there seem to be two cases. One is the test function working intermittently and the second is weather or not the engine and fuel lights would come on if needed. Clearly the vac hi/low does not.  Any suggestion where to start troubleshooting process?

Hank Grand Master

Hank

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7 minutes ago, ArtVandelay said:

Are you turning on your nav lights?

Or panel lights? I thought I had some weirdness, then noticed the panel light rheostat--turned it fully CCW, all the other lights came right up!

rotorman Community Regular

rotorman

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1 hour ago, Hank said:

Or panel lights? I thought I had some weirdness, then noticed the panel light rheostat--turned it fully CCW, all the other lights came right up!

Nav and panel lights were off. If one or the other were on, would it not also affect the ram air light? That light functions when I pull the knob out. But it does not test.

carusoam Grand Master

carusoam

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If you have the chance to look through the MM wiring diagrams...

There are a lot of parts inside that annunciator box...
 

Best regards,

-a-

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rotorman Community Regular

rotorman

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12 hours ago, PT20J said:

It sounds like some issue with the internal power supply. The annunciator was made International Avionics, Inc. I'd call them and see what they say https://www.internationalavionics.com/

Skip

 

Any chance this could be related to the engine swap? Like wiring from the engine sensors to the annunciator? It started on the initial flight after the swap

PT20J Grand Master

PT20J

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1 hour ago, rotorman said:

Any chance this could be related to the engine swap? Like wiring from the engine sensors to the annunciator? It started on the initial flight after the swap

It's hard to know, but I don't believe that the annunciator has any direct connections to the engine compartment. The service manual has some schematics for the 28V systems buy not much info on the 14V. In the 28V systems, the TEST function is just a pushbutton off the 28V input. The first thing I would check is the bus and ground connections to the annunciator panel.

Skip

rotorman Community Regular

rotorman

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A bit of troubleshooting today gave me a few clews.  The annunciator test function worked prior to the flight but failed sometime during the hour and was inop prior to landing. I hangared the airplane and it worked again in about 15 min  So heat may be the culprit.  The second thing is that I can duplicate the problem by pulling the annunciator circuit breaker.  When power is applied to the airplane the gear light is on and the vac hi/lo light is on. Ram air is on if the knob is pulled.  If the annunciator circuit breaker is pulled the only light that goes out is the vac hi/low. The other two remain on.  The problem could be with the circuit breaker but more likely in the annunciator box. 

On Skip's advice, I will call International Avionics tomorrow and see if they have any ideas. In the meantime, I would like to know how to change a circuit breaker. What sort of disassembly is involved. It doesn't look easy.

carusoam Grand Master

carusoam

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Nice detailed update RM!

I’d look forward to calling those guys...

Their website doesn’t have much detail...

But... they did have this really cool piece of art... :)

By Richard R Broome 

-a-

4B15DB26-F0BD-4136-8B0F-4FFFDC45D9FE.jpeg

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rotorman Community Regular

rotorman

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I called Avionics international with my annunciator problem. Spoke with Kenneth. Learned the the power supply wire is on the far right side of the 15 wire connector. I can probe that with a multimeter for 14v while the unit is failed and again when the unit comes back to life. If it is not the power supply then they can rebuild the unit. $650.

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PT20J Grand Master

PT20J

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On 10/6/2020 at 4:43 PM, rotorman said:

A bit of troubleshooting today gave me a few clews.  The annunciator test function worked prior to the flight but failed sometime during the hour and was inop prior to landing. I hangared the airplane and it worked again in about 15 min  So heat may be the culprit.  The second thing is that I can duplicate the problem by pulling the annunciator circuit breaker.  When power is applied to the airplane the gear light is on and the vac hi/lo light is on. Ram air is on if the knob is pulled.  If the annunciator circuit breaker is pulled the only light that goes out is the vac hi/low. The other two remain on.  The problem could be with the circuit breaker but more likely in the annunciator box. 

On Skip's advice, I will call International Avionics tomorrow and see if they have any ideas. In the meantime, I would like to know how to change a circuit breaker. What sort of disassembly is involved. It doesn't look easy.

I’m a little confused. On my airplane (SN 24-3340, 28V), test will not illuminate any annunciators when the Annunciator CB is pulled. The Gear Down light illuminates continuously with gear down and the Gear Warn CB    in whether the Annunciator CB is in or pulled. If you are getting lights to illuminate with test when the Annunciator CB is pulled, then the first thing to do would be to figure out where the power is coming from. 

Skip 

rotorman Community Regular

rotorman

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Skip

I answered this a few days ago but don't see my reply. That's a mystery.

 

We are saying the same thing, I believe. The only difference is that I have a ram air light which stays on with the gear light  when I pull the annunciator CB. Everything else goes dark. This tells me that ram air is on a separate breaker from the annunciator. When my annunciator test light fails in flight it looks exactly as if I pulled the CG  And once I get to home base, I will check the voltage at the CB and the annunciator connector if I can get it to fail on the ground. There's nothing worse than an intermittent failure to cause troubleshooting difficulties. 

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