67 M20F Johnson Bar Mooney with Intermittent Gear Down Light

[Sheriff23]

Manual Johnson Bar Mooney Owner here. 

On my flight yesterday, my gear down and locked green light was intermittent when I put the gear down.  I cycled the gear and it remained the same.  

I raised the gear and remained airborne to troubleshoot.  The gear down green light press-to-test worked as advertised with a bright solid green light.  

Depressing the gear switch manually (with he gear up) initially did not turn on the gear down switch, but after cycling it a few times it would result in a solid green light with the switch depressed.  

I lowered the gear again and the light was intermittent to solid, but not as bright.  Rotating the locking sleeve did make the remain more steady and less intermittent, but was not a solid bright green.

The Johnson bar is solidly locked and fully seated.  With the gear down a solid hard pull will not unseat the Johnson bar.  

Annual was completed in April and the downlock block was checked and in good shape, not requiring replacement. 

My initial assumption is the gear switch in the block is going bad.  Is it adjustable if it somehow became bent so the Johnson bar is not fully depressing it?  Otherwise, I may need to get with a local shop to have it replaced.  

Has anyone had this issue and did replacing the switch resolve the issue?  Also, does anyone have details on who sells the switches?

[M20F]

Those lights need to be twisted on occasion to make contact. My red light is suspicious in the best of times as it is too close to the eyebrow light on my AI and doesn’t contact real well.  Would start with tightening/loosening them a bit first.  Cheap and easy.  
 
That being said even working the pressure switch will indicate green when it isn’t locked fully in certain configurations.  I always just feel the click and give it a few pulls going base to final.  The lights are nice and legally required but I tend to ignore them.  That was why I wanted the manual gear.  You 100% know when it is up or down.   

[Sheriff23]

2 hours ago, M20F said:

Those lights need to be twisted on occasion to make contact. My red light is suspicious in the best of times as it is too close to the eyebrow light on my AI and doesn’t contact real well.  Would start with tightening/loosening them a bit first.  Cheap and easy.  
 
That being said even working the pressure switch will indicate green when it isn’t locked fully in certain configurations.  I always just feel the click and give it a few pulls going base to final.  The lights are nice and legally required but I tend to ignore them.  That was why I wanted the manual gear.  You 100% know when it is up or down.   

The lights press to test good.....I checked that and in flight with the gear up depressing the switch activates the light now.....It is just with the gear down that the light is intermittent.  

[Igor_U]

On 8/15/2022 at 10:17 AM, Sheriff23 said:

Manual Johnson Bar Mooney Owner here. 

.............

Has anyone had this issue and did replacing the switch resolve the issue?  Also, does anyone have details on who sells the switches?

Sheriff,

Just yesterday, while completing the annual inspection, I spent few ours on my back under the panel diagnosing the landing gear warning system. Lights were working OK sometimes red would be somewhat dim.

On mine, the horn would not sound with gear up and reduced throttle. Horn was tested good and seems that issue was a manual gear switch (BZ-7-RWT80).

I had some really inconsistent measurements on DVM - output going into Throttle position switch was 8.9 VDC that would go down to 1.0. Removing switches and cleaning with contact cleaner brought the Horn up to  life and scared me to death!

All working now.

 

Anyway, googling the switch p/n showed it at Grainger for $25.00. I might just buy it for a spare. Our plane (born side by side in the factory) are well over 55y old and electrical connection can have a lot of corrosion, switches warn and such…

Good luck solving your issues.

[Sheriff23]

Sheriff,
Just yesterday, while completing the annual inspection, I spent few ours on my back under the panel diagnosing the landing gear warning system. Lights were working OK sometimes red would be somewhat dim.
On mine, the horn would not sound with gear up and reduced throttle. Horn was tested good and seems that issue was a manual gear switch (BZ-7MRT80).
I had some really inconsistent measurements on DVM - output going into Throttle position switch was 8.9 VDC that would go down to 1.0. Removing switches and cleaning with contact cleaner brought the Horn up to  life and scared me to death!
All working now.
 
Anyway, googling the switch p/n showed it at Grainger for $25.00. I might just buy it for a spare. Our plane (born side by side in the factory) are well over 55y old and electrical connection can have a lot of corrosion, switches warn and such…
Good luck solving your issues.

Igor,
Thanks for the input. Aside from being under the panel is the switch easy to access and clean the contacts? Or did you have to remove the switch?


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[Igor_U]

Plane has to be on the jacks to retract the gear and remove the switch. i can't see another way but then it was annual time.  I also removed the small plastic trim piece in front of the down lock... 

[47U]

34 minutes ago, Sheriff23 said:

Aside from being under the panel is the switch easy to access and clean the contacts?

I took this picture 4 years ago when I replaced my down lock block.  You ‘might’ be able to fish a contact cleaner straw up to the switch contacts.  

@Igor_U has the right idea.  I think you’d want to be on jacks so you can exercise the switch while applying the contact cleaner.  Whether you can get enough spray into the contacts without removing down lock block is unknown, but might worth trying.  If you do have to remove the down lock block, you’re already on jacks.

Here’s the other side showing the switch mounting screws to the down lock block switch bracket.

[Shadrach]

I don’t know if the switch itself is easily adjustable but the lever that actuates it is flexible and can be tweaked slightly to change how close it is to the bottom of the socket. It’s a simple micro switch, but it’s a PITA to access.

Better to have a light that is flakey with the gear down and locked than to have one that illuminates when the gear is not locked.