M20M flaps operating intermittently

[PDXBravo]

Typically stuck full up. I'm told I need a new flap preselect relay assembly. Any experience with this problem or alternative to what I'm told is a $1700 part?

 

 

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[mooneyflyfast]

Could be but I would get a second opinion. My flaps wouldnt come down a couple of weeks ago in my J. Turned out that the llimit switch needed to be rerigged.. 0 parts cost. 

[Cruiser]

more likely the limit switch. Located in the belly. 

[mike_elliott]

1 hour ago, Adam Stites said:

 

Typically stuck full up. I'm told I need a new flap preselect relay assembly. Any experience with this problem or alternative to what I'm told is a $1700 part?

 

 

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That is typically what is wrong with them on the Bravo/long bodies. One could replace just the bad relay on the PCB since it would qualify as an industry standard part for much much less. You might consider pulling out the PCB and let Mr. Google help you identify the relay. In any event, you could test the relays ( think there are 2 on the board) that way prior to ponying up for the new PCB from Mooney. 

Mooney had experienced other owners with the same issue and they created a retrofit kit to upgrade the relays to higher amperage rated relays.  The upgrade kit was Mooney Retrofit Kit IAW DWG 940090. 

[carusoam]

Search for limit switches around here...

They are commercially available according to the thread.

Getting a Mooney part number printed on the outside of it is pretty expensive...  

Best regards,

-a-

[LANCECASPER]

On 11/17/2017 at 2:52 PM, Adam Stites said:

 

Typically stuck full up. I'm told I need a new flap preselect relay assembly. Any experience with this problem or alternative to what I'm told is a $1700 part?

I was told the same thing. You may not. What I needed was one of these (W67RCSX-3). One of mine showed a burned spot through the clear housing.

 

I replaced both and haven't had a problem since. (There is one for Up and one for Down).

Here are some of the relays available right now: (https://www.ebay.com/itm/MAGNECRAFT-P-W67RCSX-3-DPDT-24VDC-5A-SLDR-LGS-RELAY-NEW-1-/152310990373)

 

[thinwing]

Advanced hangar fairy 

[Yetti]

contact cleaner spray can.  exercise and flush limit switches with contact cleaner in liberal amounts  To start with.  Then move to relays.

If the relay was gone, they would not go up or down at all.

Edited November 22, 2017 by Yetti

[triple8s]

On 11/17/2017 at 5:03 PM, mike_elliott said:

That is typically what is wrong with them on the Bravo/long bodies. One could replace just the bad relay on the PCB since it would qualify as an industry standard part for much much less. You might consider pulling out the PCB and let Mr. Google help you identify the relay. In any event, you could test the relays ( think there are 2 on the board) that way prior to ponying up for the new PCB from Mooney. 

Mooney had experienced other owners with the same issue and they created a retrofit kit to upgrade the relays to higher amperage rated relays.  The upgrade kit was Mooney Retrofit Kit IAW DWG 940090. 

Relays with same P/N as on a 1996 M20R can be had for aproximately 40$ if the old ones could be desoldered and replaced. "If" ; )

[Cyril Gibb]

On 2017-11-22 at 10:36 AM, Yetti said:

If the relay was gone, they would not go up or down at all.

It depends.  When you energise the down relay to provide 12v to the actuator, the up relay has to provide ground to the other side of the actuator via its normally closed contact.  Opposite is true when you actuate the up relay, the down relay provides the ground.

So you can get motion in one direction but not both if either of the up or down relays has a problem with the normally open or normally closed contacts.

In the case of 1975 Mooney flap relays, the active contact (NO) is rated at 20 amps and the ground (NC) is unfortunately rated at only 10 amps.  Ask me how I know.  And that’s the retrofit replacement.

[Yetti]

Agree.  The title included intermittent.  That means they go up and down sometimes.   so the relays are mostly working.  I had a case where if I went half flaps they would not go up.  but If I went to full flaps then they would come up.   a fair amount of contact cleaner on the limit switches and working them between sprays.  good to go.

[Cyril Gibb]

On 11/18/2017 at 8:46 AM, LANCECASPER said:

I was told the same thing. You may not. What I needed was one of these (W67RCSX-3). One of mine showed a burned spot through the clear housing.

I checked that part number spec.  Those relay contacts are rated at 5 amps.  What's your flap circuit breaker value?

I recently burned out a retrofit (supposedly more robust) relay, where the normally closed contact is rated at 10 amps and my flap circuit breaker is 15 amps.  It seems that the relays are under spec and will blow before the circuit breaker pops if the flap motor is under heavy load often enough.  Poor design to have components with lower power ratings than the breaker protecting them.

Whipping up a replacement circuit board with 20 amp relays would only be about $30Cdn in parts (less in $Usd).  I assume that would require a PMA and piles of paperwork to make up your own.

Could that be considered to be an owner supplied/manufactured part in the US?

[cliffy]

Circuit breakers a designed to protect the wiring and not the units attached down line.They stop the wiring from catching fire. 

Just because the C/B says 10 amps doesn't mean the unit down line uses 10 amps

An owner could (theoretically) design a replacement relay board using  mil spec relays or even standard part relays (if they qualify as standard parts) as an "owner designed part" and not need a PMA.  PMAs are only required to manufacture parts for sale to others.  

[LANCECASPER]

22 hours ago, Cyril Gibb said:

I checked that part number spec.  Those relay contacts are rated at 5 amps. 

The original relay (above part number) lasted 25 years - that seems like pretty good reliability.

[thinwing]

If you decide to replace the relays on the pc board..do your self a favor and get lots of desoldering copper braid,desoldering suction iron,hot air surface mount gun...etc ..the problem is getting all pins free at the same time..one still soldered and "holding" means a ripped trace...practice removing components on a junk board

[LANCECASPER]

On 11/28/2017 at 3:11 PM, thinwing said:

If you decide to replace the relays on the pc board..do your self a favor and get lots of desoldering copper braid,desoldering suction iron,hot air surface mount gun...etc ..the problem is getting all pins free at the same time..one still soldered and "holding" means a ripped trace...practice removing components on a junk board

On the original flap design on the M20M the relay just plugs into sockets and unplugs, no desoldering or soldering.

EDIT: But according to the post below if you have the retrofit kit then they are soldered on the board. Another good reason to stay with the original circuit design if possible and just replace a relay if it goes bad. Others may have had different experiences but one plug and play relay replacement on the board in 25 years seems like a good design to me.

SIDE VIEW WITH NICE SHINY NEW PLUG-IN RELAYS

BOTTOM VIEW

[Cyril Gibb]

My 75F has the retrofit kit from Mooney.  It's a single printed circuit board with the two relays soldered in.  So it seems there's some with socketed relays and some with not.

[PDXBravo]

Gentlemen: I wanted to circle back and let you know that, as a result of your experiences, we were able to replace the limit switches at a cost of $30 vs the entire preselect relay board for $1700. The flaps worked flawlessly all day in my flight (city, desert, and ocean) across Oregon. A big thanks for everyone who commented here.


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[carusoam]

Great follow-up pdxb!

Best regards,

-a-