M20J Gear Retraction Troubleshooting

[PT20J]

Put the gear switch up and gear did not retract. No breakers popped and emergency extension lever was latched down. No warning horn and override button did not illuminate, but I pressed it anyway to no effect. I put the gear switch back down and landed. Jacked the airplane and confirmed no retraction and no sounds or current draw when the gear switch was placed in the up position. Removed belly, checked wiring (all secure) and tapped gear up relay with screwdriver handle. Gear now retracted. Let gear retract to halfway position and pulled gear actuator breaker. Exercised gear switch in both directions several times noting sound of both relays actuating. Put gear back down, took airplane off the jacks and ordered two relays.

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[N201MKTurbo]

Can you take apart the relay and clean the contacts? If it is the relay you posted on the other thread, it looks like you can.

[PT20J]

15 minutes ago, N201MKTurbo said:

Can you take apart the relay and clean the contacts? If it is the relay you posted on the other thread, it looks like you can.

Maybe. The problem is that I really don't know what's wrong with it. I did not hear it activate until after I thumped it with the screwdriver, so it might be a mechanical problem. And, the trouble with cleaning contacts is that if the plating has worn through, they will just oxidize again anyway.

[Ragsf15e]

Some of these relays (possibly not on your newer model) are electronic switches mated to mechanical plungers.  I haven’t taken one apart, but it would be interesting to see which part failed?

Edit: oh, I see yours is the solenoid.  I was thinking it was an up limit switch…

Also, consider yourself lucky that it didn’t work perfectly on the ground and for the next 3 weeks and fail again on an ifr flight at max gross weight… intermittent problems are the worst.

[PT20J]

Fortunately the relays are available and $300 for an airplane part doesn't seem all that terrible.

https://peerlesselectronics.com/6041h220-relay

 

[N201MKTurbo]

1 hour ago, PT20J said:

Maybe. The problem is that I really don't know what's wrong with it. I did not hear it activate until after I thumped it with the screwdriver, so it might be a mechanical problem. And, the trouble with cleaning contacts is that if the plating has worn through, they will just oxidize again anyway.

All I have taken apart have solid copper contacts. They get pitted and burned. They clean up very well. If the solenoid doesn’t work, that is another thing all together.

After you put in the new ones, take the bad one apart and post some pictures.

[Fly Boomer]

6 hours ago, PT20J said:

Fortunately the relays are available and $300 for an airplane part doesn't seem all that terrible.

https://peerlesselectronics.com/6041h220-relay

 

Were you able to track that down using info in the IPC?

[PT20J]

49 minutes ago, Fly Boomer said:

Were you able to track that down using info in the IPC?

It is listed in the IPC and in the back of the Service and Maintenance Manual which lists all the electrical components on the schematic. Sometimes the Service Manual is a better source than the IPC for electrical components.

[PT20J]

Relays replaced. Interesting that the new relays made by SAFRAN are made in the USA. I took the old UP relay apart. The contacts appear plated with some metal. They are pitted, though not too badly. However, there was an audible squeak when the plunger was moved and it shows a shiny wear spot in one location visible in the photo. I'm pretty sure the failure was caused by the plunger sticking rather than the contacts. 

[EricJ]

17 minutes ago, PT20J said:

Relays replaced. Interesting that the new relays made by SAFRAN are made in the USA. I took the old UP relay apart. The contacts appear plated with some metal. They are pitted, though not too badly. However, there was an audible squeak when the plunger was moved and it shows a shiny wear spot in one location visible in the photo. I'm pretty sure the failure was caused by the plunger sticking rather than the contacts. 

Gonna rehab that for a spare or just leave the corpse in the morgue?

[PT20J]

6 minutes ago, EricJ said:

Gonna rehab that for a spare or just leave the corpse in the morgue?

I saved the down relay for a spare and I'm going to trash this one.

[A64Pilot]

Been over 40 years ago but I worked at a warehouse that had electric forklifts, they had big relays that carried huge current. Points were open and easily visable.

They would quit working correctly from burnt points and we would clean them, they appeared to be solid copper, but once they were cleaned they didn’t last, they would need cleaning frequently until they were replaced.

Most anyone who lives down South has had their air conditioning quit working from ants getting into the main power relay and being fried, cleaning the points will get it working but it won’t last long, even if the ants don’t return.

Many switches and relays are designed to be self cleaning, I think maybe some kind of wiping action of the contacts maybe, but even those once the points burn don’t last if cleaned.

Same with distributor points back in the day, you could file the points and many files were sold just for this, but once filed they didn’t last long.

So what I’m saying is by all means if you have to file or otherwise clean contact points or use contact cleaner to get home but more than likely it’s a temporary fix, start trying to find a replacement.
I’m convinced some switches / relays etc just age out, their contacts corrode, not wear out. 

My landing gear switch went bad and my airplane has 2,000 hours on it, I doubt it wore out, but it was 42 years old.

 

[Will.iam]

On 5/18/2023 at 1:41 PM, PT20J said:

Fortunately the relays are available and $300 for an airplane part doesn't seem all that terrible.

https://peerlesselectronics.com/6041h220-relay

 

Wow inflation really kicking in that part is now $439! A 46% increase in less than a month!

[201Mooniac]

I just checked and it is now up to $445, seems to be increasing by about a dollar an hour.  That is real inflation!