Annunciator panel test function, RIGHT FUEL LOW Lamp

[Martin S.]

Evening everybody,

the right tank "low fuel lamp" of my annunciator panel (1978 Model) does only work sporadically when pressing the test button. It mostly works when the tank is really full. Is this a common issue and has anybody an idea of how to repair these units without having them expensively overhauled? If the overhaul is the only solution, has anybody an idea of where to do this and how much it approximately is?

 

Greets from Germany,

 

Martin 

[PT20J]

There is a damping circuit in there to keep it from flickering when the fuel level is right at the set point. Are you holding the button down long enough?

[Martin S.]

2 minutes ago, PT20J said:

There is a damping circuit in there to keep it from flickering when the fuel level is right at the set point. Are you holding the button down long enough?

Good point, yes - varied both pressing force and duration.

[PT20J]

6 minutes ago, Martin S. said:

Good point, yes - varied both pressing force and duration.

Figured you had probably done that, but it was worth a shot.

I believe that the OEM may still able to repair them https://www.internationalavionics.com/

Here is the troubleshooting info from the Service Manual if you want to take a shot at fixing it yourself.

 

[ArtVandelay]

FWIW, but under USA guidelines you can get rid of the annunciator or disable functions if you replace functionality with other certified equipment.
So if you install a certified engine monitor that will give you fuel warnings like JPI 900, you can just remove the light bulbs for the fuel warnings and remove the other engine gauges to gain some panel space.
I removed the annunciator completely:

[Martin S.]

8 minutes ago, PT20J said:

Figured you had probably done that, but it was worth a shot.

I believe that the OEM may still able to repair them https://www.internationalavionics.com/

Here is the troubleshooting info from the Service Manual if you want to take a shot at fixing it yourself.

 

Thanks - very helpful! Maybe a stupid question but is there any possibility the test function reacts differently, depending on whether the engine is running or not?

[PT20J]

3 minutes ago, Martin S. said:

Thanks - very helpful! Maybe a stupid question but is there any possibility the test function reacts differently, depending on whether the engine is running or not?

I doubt it -- it's all just electrical circuitry. The only difference with the engine running that I can think of would be a higher bus voltage assuming the rpm is above the alternator cut-in speed.

[Martin S.]

3 minutes ago, ArtVandelay said:

FWIW, but under USA guidelines you can get rid of the annunciator or disable functions if you replace functionality with other certified equipment.
So if you install a certified engine monitor that will give you fuel warnings like JPI 900, you can just remove the light bulbs for the fuel warnings and remove the other engine gauges to gain some panel space.
I removed the annunciator completely:

Yesss - getting rid of 70s electronics/avionics is always good :). I don't see a test function for the gear down lamp in your new setup. Didn't you have to find a replacement for that functionality.

Slightly off topic: It looks like you replaced some of the switches/switch covers. If yes, are these 3D printed ones? Very interesed in these - one of mine just broke today - arrrrg.

[Martin S.]

4 minutes ago, PT20J said:

I doubt it -- it's all just electrical circuitry. The only difference with the engine running that I can think of would be a higher bus voltage assuming the rpm is above the alternator cut-in speed.

Roger - will play a little bit more with it and see if I can find an error/failure pattern, before considering to remove/overhaul.

[ArtVandelay]

Yesss - getting rid of 70s electronics/avionics is always good . I don't see a test function for the gear down lamp in your new setup. Didn't you have to find a replacement for that functionality.
Slightly off topic: It looks like you replaced some of the switches/switch covers. If yes, are these 3D printed ones? Very interesed in these - one of mine just broke today - arrrrg.

No, all those lights have a push to test function. The gear down lettering is just a little worn.

I did not replace the switches, they’re original AFAIK.

[kortopates]

Cost to overhaul these units by the manufacturer is only about $400 US a couple years ago. New screens are getting rarer though. I kept my annunciator even though i have a EDM-900 as i believe they look far more modern than individual press to test 60’s era gear lights. Plus i still have more than gear down lights (vacuum high/low, Volts high/low only used by Speed Brakes now and Starter on).
Additionally, at the top of the panel it occupies nothing else would fit there anyway.


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[Martin S.]

This little unit has its phases. Went flying yesterday. It worked during the check, with master on and engine off. But I realized the function is quite lazy: It takes like 0.5 sec after pressing the button, until the lights go on. Forgot to test it again though during the flight. 

 

[Martin S.]

4 hours ago, kortopates said:

Cost to overhaul these units by the manufacturer is only about $400 US a couple years ago. New screens are getting rarer though. I kept my annunciator even though i have a EDM-900 as i believe they look far more modern than individual press to test 60’s era gear lights. Plus i still have more than gear down lights (vacuum high/low, Volts high/low only used by Speed Brakes now and Starter on).
Additionally, at the top of the panel it occupies nothing else would fit there anyway.


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Thanks for the info. Will consider overhauling it. Its not even necessarily the price, more the fact of grounding the bird for moody seventies electronics - haha.

[kortopates]

Thanks for the info. Will consider overhauling it. Its not even necessarily the price, more the fact of grounding the bird for moody seventies electronics - haha.

they’re trouble free, in my 20+ years it’s only needed a light bulb till avionics tech plugged the cable in backwards frying about 8 diodes - hence why i know the overhaul cost.


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