Down Limit Switch - Help

[moon_dog]

Hi all, apparently I have a bad down-limit switch in my M20F. The symptom is that the gear down light is intermittent and doesn’t come on right away when the gear goes down. Sometimes takes way too long to come on and is quite disconcerting in the pattern. 

Anyway, I need a replacement. The Lasar part is the Otto P6-24014. It’s almost a grand and is a special order item. 

Does anyone know of an alternative to this part? Or where I might be able to find a good used one?

Thanks in advance!

Edited April 11, 2023 by moon_dog

[carusoam]

wait…

You have electric gear….  
 

contact @Alan Fox

Or clean the switch…

Best regards,

-a-

[PT20J]

41 minutes ago, carusoam said:

wait…

You have electric gear….  
 

contact @Alan Fox

Or clean the switch…

Best regards,

-a-

According to the specs, it’s sealed.

[PT20J]

+1 for @Alan Fox

Search the part number online.

Call an Otto distributer.

Call other Mooney Service Centers

[LANCECASPER]

6 hours ago, moon_dog said:

Hi all, apparently I have a bad down-limit switch in my M20F. The symptom is that the gear down light is intermittent and doesn’t come on right away when the gear goes down. Sometimes takes way too long to come on and is quite disconcerting in the pattern. 

Anyway, I need a replacement. The Lasar part is the Otto P6-24014. It’s almost a grand and is a special order item. 

Does anyone know of an alternative to this part? Or where I might be able to find a good used one?

Thanks in advance!

https://peerlesselectronics.com/p6-14000-switch

They have 146 in stock.

[PT20J]

3 hours ago, LANCECASPER said:

https://peerlesselectronics.com/p6-14000-switch

They have 146 in stock.

That's not the same part number, though. Mooney used a P6-24014. 

Otto doesn't list the Mooney part in their current catalog. I would call them and see if there is a cross reference. https://www.otto-controls.com/-/media/products/electromechanical-switches/limitswitches/p6sealedlimitswitchesmilprf8805/p6-sealed-limit-switches-catalog-page.ashx

[moon_dog]

20 minutes ago, PT20J said:

That's not the same part number, though. Mooney used a P6-24014. 

Otto doesn't list the Mooney part in their current catalog. I would call them and see if there is a cross reference. https://www.otto-controls.com/-/media/products/electromechanical-switches/limitswitches/p6sealedlimitswitchesmilprf8805/p6-sealed-limit-switches-catalog-page.ashx

Correct. I called Otto this morning and the lead time for this item is 8-10 weeks...

Curious if a similar product is approved for use. 

Definitely ramping up the search for a used one.

[LANCECASPER]

1 hour ago, PT20J said:

That's not the same part number, though. Mooney used a P6-24014. 

Oops!  

[Ragsf15e]

You should call DMax and talk to him (Don Maxwell Mooney, Longview TX).  

I called and talked to him a few years ago and he gave me some specific part numbers.  I ended up lubing mine and (fingers crossed), it's been ok since.  However, I looked up the part numbers and they appear to be two components that actually make up the switch.  I'm not saying these are right - in fact they look different than yours, I'm saying you should call him, but I'm going to attach below so you can see...

I'm now curious because your limit switch looks much different than mine (1968 F).  What year is your F?  Mine look more like the ones Don told me about.  Maybe there is an alternate part you could use?  I'll attach a (crappy) picture of my limit switch - it's black and cube shaped, definitely different than yours.  Sorry about the picture, but it's in the bottom left.

MCD2711 - https://www.mouser.com/ProductDetail/Honeywell/MCD2711?qs=0x4sLrpp94KewLfSyp6k4A%3D%3D&gclid=CjwKCAjwitShBhA6EiwAq3RqA3nvmhMJynIznYPuCs0H7iLE9sKi8PtiUNmwOAOwZtTGgGje0yvq4hoC8iQQAvD_BwE

DT-2R-A7 - https://www.grainger.com/product/24A126?s_kwcid=AL!2966!3!606773749412!p!!g!!__EFKW__&gucid=N:N:PS:Paid:GGL:CSM-2296:AB578S:20500731&gclid=CjwKCAjwitShBhA6EiwAq3RqA9tu1iox7sux-IPLhsfy64P0hAF2rVytkY-OTvqT4M5_rR5B5o4AFhoCNh4QAvD_BwE&gclsrc=aw.ds

 

[moon_dog]

Turns out the Honeywell 1CH1-6 is also used in these airplanes and I was able to locate a used one at BAS. It's en route. We will see...

[Ragsf15e]

5 minutes ago, moon_dog said:

Turns out the Honeywell 1CH1-6 is also used in these airplanes and I was able to locate a used one at BAS. It's en route. We will see...

What year is your airplane?  The switch looks much different than my picture above?

[201Steve]

@moon_dog did you have luck with the 1ch1-6 as a down limit switch? The IPC calls out that part number as used for the gear squat switch (if so equipped). They appear identical to the 1ch116-6 which is the official down limit switch part number, but it seems some resellers call out the 1ch1-6 as a Mooney gear limit switch. 

[FLYFST]

On 4/11/2023 at 5:54 PM, moon_dog said:

Turns out the Honeywell 1CH1-6 is also used in these airplanes and I was able to locate a used one at BAS. It's en route. We will see...

Moon_Dog, I've had similar issues with my 1990 J model, and what worked out best was adjusting the switch stop (tab secured to the push-pull rod) so that it contacts the plunger face flat instead of at an angle.  My A&P previously tried lubing the plunger with CRC contact cleaner with immediate results that did not last much.  As a sealed switch, about the only place the lubricant could be of some effect is on the plunger, and that actually looked very good and corrosion free in my case.  My switch appears to have been replaced from the original and it is currently an Otto Controls P6-24014 alternate part number in the IPC.  When I called LASAR earlier this year looking for a Honeywell 1CH116-6 switch they told me that switch was no longer available, but recommended alternate part number P6-24014 (what I have now), and which in March 2024 was $1,152 new but out of stock.  They also suggested using another alternate part number 1EN1S priced at $1,768 and one was available then from the Mooney factory.

[201Steve]

@moon_dog did you have luck with the 1ch1-6 as a down limit switch? The IPC calls out that part number as used for the gear squat switch (if so equipped). They appear identical to the 1ch116-6 which is the official down limit switch part number, but it seems some resellers call out the 1ch1-6 as a Mooney gear limit switch. 
 

 

good feedback thanks! I just found the 1EN1S for a almost reasonable $460

[A64Pilot]

Ref cleaning switches, by all means do so as a temp measure, but be aware it’s almost always a temporary fix as most switches have some kind of plating on them and most of the time they get intermittent when this plating wears off and cleaning won’t of course replace the plating. Switches that trigger a relay so that they are only carrying a tiny amount of power last a very long time as opposed to those that carry significant amount of current due to arcing of the contacts.

Then all contact cleaners are not created equal, I’ve had the best luck with Deoxit, it’s not cheap but compared to the price of these switches it’s just pennie’s.

Ref are there any other approved switches? Download and read this AC ref parts substitution for antique aircraft, ALL Mooney’s are antique aircraft and this AC covers every Mooney ever made, in particular electrical parts are about the easiest to substitute, many if not nearly all are Standard Parts.

So look up Standard parts, I think if you could find a switch that would work and carry the amperage then yes it’s approved. I would quote this AC in the logbook entry though.

This AC has been out since 09, so 15 years? Not likely to change and surely every FAA inspector is aware of it.

https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC_23-27.pdf

On edit, I use contact cleaner as a troubleshooting measure, if the problem goes away when I clean a switch, then it’s likely that’s the problem so I try to find a switch.

Edited November 2, 2024 by A64Pilot

[FLYFST]

Has anyone confirmed that the 1EN1-6 or 1CH1-6 limit switch is a Mooney-approved replacement for the Honeywell 1CH116-6 switch listed in the Mooney IPC?  

Best research I have found so far was from Skip (PT20J) who noted the 1CH1-6 is essentially the same as the now obsolete 1CH116-6, but that circuit specification stated that one circuit must close slightly before another, presumably to make the motor shut down before the gear light comes on, and the 1CH1-6 does not include that feature.  I'm searching for a replacement to the Otto Controls P6-24014 switch that I have and while the 1CH1-6 seems to be viable, I am concerned about the circuit difference that Skip found in the following post.

 

[PT20J]

I cannot imagine that the requirement that one set of contacts makes first makes a difference. According to the specification, the difference in plunger travel between the two sets of contacts making is only  .010 +/-.005". If you are really concerned about it, you could call Frank Crawford.

[EricJ]

Another potential strategy is to try it and see if it passes op checks.   If the environmental (temperature, etc.) and electrical (current capability, etc.), etc.,  specs are suitable for the application that may be a reasonable way to proceed.   Consult with your IA.

[oisiaa]

Will this switch sticking prevent extension? I have a 1971 C model that has an issue with the gear not coming down. The shop cleaned the switch last month, but this morning the gear didn't come down again so I'm looking to have the switch replaced. Just sanity checking that the switch sticking will prevent extension before I spend the money on a new switch.

My gear eventually came down after maybe 10 minutes with the gear switch in the down position as I was setting up to manually extend the gear.

Edit: Just thinking though this, it makes sense to me that if the switch says that the gear is down, then power to the motor would be removed. I'll check the service manuals when I get home for schematics.

Edited October 13, 2025 by oisiaa

[PT20J]

Could be the switch; could be the relay. Hard to tell which if intermittent. You could replace both to be certain. Or you could start by replacing whichever is cheaper. 

[oisiaa]

I found a used 1CH1-6 down limit switch for $75 from BAS vs the near $1,200 that LASAR wants for a new one (plus an 8 week lead time)...I'm going to take my chances for such a price difference. 

Edited October 15, 2025 by oisiaa

[EricJ]

18 hours ago, oisiaa said:

I found a used 1CH1-6 down limit switch for $75 from BAS vs the near $1,200 that LASAR wants for a new one (plus an 8 week lead time)...I'm going to take my chances for such a price difference. 

Maybe the guys from Lasar will buy BAS and raise their prices, too, since clearly they're not high enough. 

[Ragsf15e]

https://us.rs-online.com/product/honeywell/1ch1-6/71145168/?srsltid=AfmBOorYGDk7FJzgHUhzXpf6yjzSKdtNGm9QSxJzeYfDC9eN5ugDF6Ry
 

those aren’t cheap, but these guys appear to have a discount vs some others…

[MikeOH]

2 hours ago, EricJ said:

Maybe the guys from Lasar will buy BAS and raise their prices, too, since clearly they're not high enough. 

@EricJ

I swear, if that happens, I'm holding YOU responsible for giving them the idea!

[Yetti]

Mouser said no longer made.

Digikey says $474 but you may have to buy 10 of them with a 36 week lead time.

https://www.digikey.com/en/products/detail/honeywell-sensing-and-productivity-solutions/1CH6-1/25328001

 

also in the original post, the limit switch controls the actuator, if switch was not working, the motor would keep running and the gear would be in a spot of bother.     Might have just had a loose ground on the warning light.