Flap issues on 1969 M20C

[Mike Gostomski]

I'm having what sounded like a common issue with older Mooneys... the flaps will go down, but will not come back up.  I read the posts about cleaning and replacing the limit switches, and was prepared to do so. When I removed the inspection panel and got a look at the flap motor, I found that there are no limit switches - at least not visible ones.  I was able to manually rotate the flap motor to get the flaps back up so I can fly it to a mechanic, but I'd like to have some idea what's going on before I take it in.

I'll attach some pictures of my flap set up. Has anyone encountered this before or have any advice?

[MikeOH]

I don't believe the limit switches are located where the actuator is.

What year/model/SN is your aircraft?  You should look at the maintenance manual and schematics.

[Shadrach]

I have no experience with the electric flaps. But my first step would be taking a multimeter to the motor to verify it is getting power with the switch in the retract position.  

Here is a thread centered on the same symptoms:

 

[N201MKTurbo]

So, on yours, it seems the limit switches are on an arm on the flap cross shaft. Your photos didn't show that.

[Mike Gostomski]

Thanks Rich!  Everything I had seen showed the switches right on the actuator.  I'll make a trip to the hangar tonight and look around a bit more!

MikeOH: Mine is a 1969 M20C Serial 690049.  I'll have to shop around for a maintenance manual.

 

[EricJ]

There have to be limit switches somewhere, so once you find them it'll probably be fairly easy to sort out.

[N201MKTurbo]

20 minutes ago, Mike Gostomski said:

Thanks Rich!  Everything I had seen showed the switches right on the actuator.  I'll make a trip to the hangar tonight and look around a bit more!

MikeOH: Mine is a 1969 M20C Serial 690049.  I'll have to shop around for a maintenance manual.

 

Follow the green cable and see where it goes. I think you will find what is in @Marauder’s post above.

[AndreiC]

Just saw that you have a 1969, probably close in production date to my 1970 M20E. I would follow @Shadrach's advice and put a multimeter to see if it gets power when actuating the switch to the up position. 

Around 1970 they put in all kinds of different flaps actuators, including some without limit switches. I know this for sure, because my 1970 has one of these. If I keep my flaps switch either up or down it will reach the limit, at which point the motor will continue to rotate for as long as I have the switch on, and just make a clicking noise every half a second. It must have some type of clutch system inside that allows it to turn without damaging the motor.

Incidentally I had the same problem as you with the flaps not going up. Turned out to be the switch that was at fault. The original switch seems impossible to find, but I sourced a replacement equivalent switch (made by the same company, just the knob looks slightly different) and my IA was OK with installing it instead. Since then no problems. I can look up the switch model if you want me to.

[Mooneymite]

On my 74 C, there were no limit switches, just an ingenious jack screw that would essentially disengage itself at the limits of travel.  For some reason, your flap motor reverse circuitry is messed up.  I'd start by checking the flap switch in the cockpit.

[MikeOH]

28 minutes ago, Mooneymite said:

On my 74 C, there were no limit switches, just an ingenious jack screw that would essentially disengage itself at the limits of travel.  For some reason, your flap motor reverse circuitry is messed up.  I'd start by checking the flap switch in the cockpit.

If the OP's plane is stock then it does have limit switches per the schematic.  I'd follow @Shadrach's advice and start with a meter at the motor and work back from there.

[Mike Gostomski]

Spent quite some time in the hangar tonight. There are no limit switches.  The toggle switch in the cockpit is the culprit.

@AndreiC - If you could share that switch's part number with me, that would be very helpful.

[AndreiC]

43 minutes ago, Mike Gostomski said:

@AndreiC - If you could share that switch's part number with me, that would be very helpful.

The switch I ordered in the end was this one:

https://www.mouser.com/ProductDetail/785-12TS15-7

It looks like they have it in stock. This was the second switch that I ended up ordering, because the first one did not have the right kind of terminals. Please check that the wires on your plane indeed have ring terminals which are held by a screw that screws into the switch (this is how my plane is) -- if that is so, then this is the right one.

Good luck with this! It was a frustrating story for me till I found this switch.

[Mike Gostomski]

That switch is ON-OFF-ON, and the one I have is ON-ON-ON.  Now that I know the issue is just the switch, I'm going to hand the rest off to my shop.

Thanks to everyone for helping me narrow down what the issue was!

[AndreiC]

9 minutes ago, Mike Gostomski said:

That switch is ON-OFF-ON, and the one I have is ON-ON-ON.  Now that I know the issue is just the switch, I'm going to hand the rest off to my shop.

Thanks to everyone for helping me narrow down what the issue was!

I am surprised yours would be wired differently from mine. What do you mean by ON-ON-ON? The way mine works is it has two 6 pins, call them ABC and DEF. In the neutral position of the switch (in the middle, where it stays if your hand is off the switch) there is no electrical conductivity between any pins (OFF). In the up position, which is momentary, pins A and B are connected to each other, and so are D and E. In the down position, which is also momentary, pins B and C are connected to each other, and so are E and F. I think this is what is meant by (ON) - OFF - (ON). 

[Shadrach]

15 minutes ago, Mike Gostomski said:

That switch is ON-OFF-ON, and the one I have is ON-ON-ON.  Now that I know the issue is just the switch, I'm going to hand the rest off to my shop.

Thanks to everyone for helping me narrow down what the issue was!

The illustrated parts catalog for the 1969 M20C is available for download below. That is the appropriate place to find part numbers.

 

[Mike Gostomski]

I'm honestly not sure what the difference is, except that the ON-ON-ON switches that I saw with a quick google search cost a heck of a lot more.  I don't know enough about electronics, and I have my day job to get back to. I'm happy to pay my mechanic to figure out the specifics in this case.

[AndreiC]

I attach here the schematic from the Mooney Maintenance Manual for your plane (and mine). If nothing else, this should be helpful for your mechanic to sort things out.

As you can see in the cross reference, the switch described as 20CF02A in the first diagram is listed as the 12TS147-70 switch that you show in your picture above. I don't know why the switch is labeled as ON-ON-ON on the casing, because the electrical diagram in the MM depicts it as an ON-OFF-ON switch as I described above.

If you or your mechanic are still confused, it may help to know that my mechanic installed the switch  listed above (12TS15-7) and it worked great with no modifications to the wiring.

Schematic 1.pdf Schematic 2.pdf

[Shadrach]

1 hour ago, Mike Gostomski said:

I'm honestly not sure what the difference is, except that the ON-ON-ON switches that I saw with a quick google search cost a heck of a lot more.  I don't know enough about electronics, and I have my day job to get back to. I'm happy to pay my mechanic to figure out the specifics in this case.

That is the correct PN.  It is does not appear to be available.  I would reach out to Honeywell to see if there is a superseding part number.

I have never disassembled one of those toggles, but there's a chance that a thorough cleaning and reassembly might make it serviceable. 

[Mooneymite]

57 minutes ago, Shadrach said:

I have never disassembled one of those toggles, but there's a chance a thorough cleaning and reassembly might make it serviceable. 

This. ^^^^^^^

[MikeOH]

48 minutes ago, Mooneymite said:

This. ^^^^^^^

Hmm, maybe... many toggle switches are factory crimped; uncrimping to open the switch and then properly recrimping the now fatigue hardened metal will be challenging.

[MikeOH]

2 hours ago, Mike Gostomski said:

I'm honestly not sure what the difference is, except that the ON-ON-ON switches that I saw with a quick google search cost a heck of a lot more.  I don't know enough about electronics, and I have my day job to get back to. I'm happy to pay my mechanic to figure out the specifics in this case.

I believe the markings are meant to show all positions are Normally Open (NO); the switch is spring loaded to return to the center position, correct?  IOW, actual electrical connections only occur when the switch is moved up or down.

[AndreiC]

6 hours ago, MikeOH said:

@AndreiCThis is VERY interesting!  The schematics I posted earlier showed limit switches and the schematic seemed to apply to the OP's serial number. Yet, his plane does NOT have the limit switches and is per the schematic you show.  What's up with that?

What's the revision date on the manual you pulled those from?

I think it's Rev H, 11/1/85. BTW, I think the schematic you posted is the one for the gear motor, not the flaps... It shows a couple of relays which are not there in the flaps circuitry.

[MikeOH]

3 hours ago, AndreiC said:

I think it's Rev H, 11/1/85. BTW, I think the schematic you posted is the one for the gear motor, not the flaps... It shows a couple of relays which are not there in the flaps circuitry.

@AndreiC

Holy Crap!!  How did I screw that up...deleted my post.  Thank you!

[sdmideas]

Hello, I have a 1971 m20c and recently had an issue with my flaps. Very similar symptoms as what has been described. I can confirm the older electric flaps do not have any limit switch. Not an ideal design. Overtime the motor will increase current consumption to the point it pops the 10a breaker.

 

I just posted an alternate part number for our motors in a new post. If you have trouble tracking down a new number you may be able to find it under the textron number. Take a look at the Cessna 150 flap actuator assembly….seems mighty familiar from a very quick visual inspection;)

 

Good luck!

[Mooneymite]

4 hours ago, sdmideas said:

Hello, I have a 1971 m20c and recently had an issue with my flaps. Very similar symptoms as what has been described. I can confirm the older electric flaps do not have any limit switch. Not an ideal design. Overtime the motor will increase current consumption to the point it pops the 10a breaker.

The 1969-75 electric flap drive is elegantly simple.  The proper greasing of the drive mechanism is apparently regularly overlooked.  If not properly greased, the resistance in the flap gearbox can...and does pop the circuit breaker.   I'm not sure why a grease cup was used instead of simple grease nipples.  I'm sure there is a good reason....?   Maybe to prevent grease-happy mechanics from blowing all the seals with a grease gun?

Edited August 30, 2024 by Mooneymite