Warning annunciator light issues

rwiseman · July 1, 2024

Chasing electrical gremlins on a 1982 J.

1. On the ground, when pressing the annunciator test switch the Left Low Fuel light does not come on. Performing the same test airborne it works every time. And when airborne it lights up correctly when left tank is low.
2. while troubleshooting an intermittent Oil Temp gauge, pulling the Cluster Gauge circuit breaker correctly removes power from all the cluster gauges and the annunciator light panel except that the Left Low Fuel light illuminates.

To trouble shoot #1, the bulbs were swapped. No luck. And the annunciator panel was replaced. Again no change in symptoms for #1.

For #2, I’m not sure where to start. Why is that light receiving power with the breaker pulled?

This may be a cross wire issue where I just leave it alone since it causes no harm, and continued troubleshooting could cause more harm than good.

Thoughts?

ArtVandelay · July 1, 2024

Annunciator is on a separate circuit with it’s own circuit breaker.

rwiseman · July 1, 2024

Hmmm. Then even more gremlins. With cluster breaker pulled, Left low fuel turns on solid and push to test turns none of the others on. I’ll reverify that. And look for a separate annunciator circuit breaker. Thx.

**PT20J** · July 1, 2024

There are schematics for the annunciator panel in the M20J Service Manual. IAI, the OEM for the annunciator, still services them and you could ask them for troubleshooting advice: https://www.internationalavionics.com/

**Marc_B** · July 1, 2024

@rwiseman There is A LOT in common with the International Avionics Inc annunciators, so I suspect that a lot of the info in my service manual could be pertinent to your situation. But I don't have the M20J service manual and I'd recommend you start there as it may have more applicable details. The pdf pages from the SM (attached below) give further infomation about the IAI annunciator and circuits.

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