gear push to test lights not working...

[funvee]

What a bunch of hypocrites...

 

Awesome!!  We have our own TROLL!  That means the forums are BIG LEAGUE now!!  

[FlySafe]

Good morning All. I'm seeking advice on my gear-up panel light before starting the gremlin hunt. This question relates to a 74 m20c ranger with electric gear. As a reminder to others not as familiar with this model, two lights: amber gear up, green gear down, off in transit, and a gear position indicator window on the floor with a dim backlight when the gear is down. In addition, there is a separate push-to-test button on the panel for the various annunciator lights.

My issue occurred on the preflight yesterday. When I pushed the annunciator test button, there was no gear-up light. However, in the following inflight test, the up indicator illuminated as expected on gear retraction. Likewise, the green gear-down light illuminated when pressing the test button inflight with the gear retracted. 

I'm pretty sure the gear-up light should, and in the past, illuminated with the push to test on preflight but now I'm questioning myself, and the POH is less than adequate. My post-flight investigation showed that the bulb tested ok on a multimeter. However, when I pushed the test button, there was no indicated power to the socket. 

Two questions:
1. I would like your help verifying that the gear-up bulb should illuminate with the push-to-test button in a 74 M20C (i saw in another thread, valid for mid-body models).
2. If true for my C, suggestions on the next step to debug

Thank you for your collective wisdom; not a EE, plain speak appreciated
k

[N201MKTurbo]

I would look at the light wiring. I would suspect a connection vibrated loose, or fractured. There is usually diodes that ground the ground side of the bulb when pushed. They have stiff leads and are prone to fracture over time.

[FlySafe]

1 hour ago, N201MKTurbo said:

I would look at the light wiring. I would suspect a connection vibrated loose, or fractured. There is usually diodes that ground the ground side of the bulb when pushed. They have stiff leads and are prone to fracture over time.

thanks Rich that is helpful. Would you or anyone @Hankhappen to have the electrical schematics for this circuit (serial number 20-0016) and knowledge on best route of access for inspection (glare shield, exterior cowl avionics panel etc). thanks in advance.

k 

[N201MKTurbo]

19 minutes ago, FlySafe said:

thanks Rich that is helpful. Would you or anyone @Hankhappen to have the electrical schematics for this circuit (serial number 20-0016) and knowledge on best route of access for inspection (glare shield, exterior cowl avionics panel etc). thanks in advance.

k 

I have the schematics for all the J models, none other.

[carusoam]

Hey…

I get a twofer tonight!

Michael was asking about the same circuits for his M20F… @MrRodgers

Soooo….

Have some pics I pulled out….

See if this helps…

 

make sure you know… the push to test lights are also twist to dim….

 

Here’s a pic of the circuit diagram for the M20F….

It comes from the Mooney Service Manual of the era…

PP thoughts only, not a mechanic…

Best regards,

-a-

 

[Hank]

10 hours ago, carusoam said:

 

make sure you know… the push to test lights are also twist to dim….

Anthony, I think this only applies to manual gear planes. The lights in my electric-gear C are behind the panel, like the other lights (low vacuum, etc.).

Yes, the white thing by the gear switch came from the factory. No, the lights don't push or turn. The dimmer knob only half visible above the altimeter adjust all cockpit lighting.

I'll check at the hangar tonight and see what schematics I may have.

[FlySafe]

Fantastic, I love the mooneyspace community, thank you all!

k

[Ragsf15e]

7 hours ago, Hank said:

Anthony, I think this only applies to manual gear planes. The lights in my electric-gear C are behind the panel, like the other lights (low vacuum, etc.).

Yes, the white thing by the gear switch came from the factory. No, the lights don't push or turn. The dimmer knob only half visible above the altimeter adjust all cockpit lighting.

I'll check at the hangar tonight and see what schematics I may have.

Depends on the year I think.  Mine has twist to dim “cat-eye” lights for the gear. It’s a 68.  I don’t have a light test switch though, just push the light to check it.

[Hank]

1 hour ago, Ragsf15e said:

Depends on the year I think.  Mine has twist to dim “cat-eye” lights for the gear. It’s a 68.  I don’t have a light test switch though, just push the light to check it.

Probably started with the 69 models, when j-bars and hydraulic flaps went away and the six pack panel arrived.

[carusoam]

Kind of the first Mooney annunciator panel…!

Nicely organized and very functional…

 

The cool part… I found the nice wiring diagrams in the service manual…

With a little more effort… serial numbers can be looked up for the exact wiring diagram as it left the factory…

 

Electric gear has a couple of places to sense or power a light…

the gear switch is probably the most likely…. But, not the best idea if the motor fails to operate….

Limit switches are next on the list… but wire runs are a bit longer… you might need to chase a wire all the way into the belly of the plane…

Squat switches come to mind… but won’t send a signal until the gear squints onto something…

 

PP guesses only…  some are better than others…

Best regards,

-a-