PC Cut off button will not come out

[DJ67]

1967 M20F has a PC button that works but if I try to pull it out to disable PC, it won't come out.  Is it possible that the O-ring has become petrified?

[Pasturepilot]

Have you had it out before? I’ll admit to damaging one by prying the wrong way- didn’t realize all the metal you see with the button comes out with the button. One of my first of several hard lessons on the Mooney after agreeing to buy it. Not until seeing a photo of the button for sale on eBay, did I realize how it came out as an assembly  

 

[takair]

32 minutes ago, DJ67 said:

1967 M20F has a PC button that works but if I try to pull it out to disable PC, it won't come out.  Is it possible that the O-ring has become petrified?

Do you mean that the spring loaded portion will not pop up?  Or do you mean you can’t remove the assembly?  Perhaps try rubbing alcohol as a temporary lubricant to loosen things up.

[carusoam]

Welcome aboard DJ...

There are a couple of ways of disabling that button...

1) Taking it out... leads to being lost... it is magnetically attracted to the hole at the base of the J-bar...

2) pushing it down works... but leads to a muscular thumb problem... when held too long...

3) A 35mm film canister is known to hold them down... ask Siri what a film canister is...

4) A large rubber band that comes traditionally with Broccoli at the grocery store can work...

5) Staples, the office supply super store may also have these magic rubber bands...

6) There is also an upscale device that can be mounted on the instrument panel... an electric valve that you can set and forget...

PP thoughts, not a mechanic...

Best regards,

-a-

[Warren Fors]

Yes, that is quite likely. But fear not, the oring is readily available and easy to replace. I owned a M20 C with the earliest PC setup. From 1991, I kept the valve out of the horn inside the door over the Breakers on the right side of the panel unless I wanted the PC or auto pilot to engage. Every so often I rubbed the tiniest amount of lip balm on the oring. In nearly 30 years it remained easy to pull and or replace.

[DJ67]

9 hours ago, carusoam said:

Welcome aboard DJ...

There are a couple of ways of disabling that button...

1) Taking it out... leads to being lost... it is magnetically attracted to the hole at the base of the J-bar...

2) pushing it down works... but leads to a muscular thumb problem... when held too long...

3) A 35mm film canister is known to hold them down... ask Siri what a film canister is...

4) A large rubber band that comes traditionally with Broccoli at the grocery store can work...

5) Staples, the office supply super store may also have these magic rubber bands...

6) There is also an upscale device that can be mounted on the instrument panel... an electric valve that you can set and forget...

PP thoughts, not a mechanic...

Best regards,

-a-

Once upon a time, in a decade far, far, away I was a 1/5th partner in a 1966 M20E.  I was taught (right or wrong) to pull the button out and stow it in the ashtray during non-PC operations.  Being a non-smoker, this made perfect sense to me.  Before posting, I read (all of) a thread on Mooneyspace about the little guy, and actually started thinking about where I might scrounge up a film canister, or would a pill bottle do the job.  But then I remembered that I have a PTT mounted adjacent to the button (see pic).  I also like the idea of the rubber band, and I've got to admit ... broccoli had got to be cheaper than lobster, which also comes with a big honkin' rubber band installed.  Another option that wasn't discussed ... you can move the clock to the copilot seat pocket and unplug the tubing ... maybe for VFR.

But getting back to my post ... I have never been able to remove the button since I bought the airplane.  I'm concerned that the o-ring had hardened and won't compress enough to let the button come out.  I can use 1 thru 5 above to disable but I wonder if the o-ring is really solidified and is going to someday fail to seal, and disable the system full-time.

Thanks everybody!

Doug

Edited July 9, 2019 by DJ67

[DJ67]

12 hours ago, Pasturepilot said:

Have you had it out before? I’ll admit to damaging one by prying the wrong way- didn’t realize all the metal you see with the button comes out with the button. One of my first of several hard lessons on the Mooney after agreeing to buy it. Not until seeing a photo of the button for sale on eBay, did I realize how it came out as an assembly  

 

It sounds like I could service the O-ring by taking the whole assembly out of the horn.  I thought about trying to dissolve it in place but was concerned about contaminating the Vac system.

So what's the trick for getting the whole assembly out?

Thanks,

Doug

Edited July 9, 2019 by DJ67

[RLCarter]

Looks like the bracket for the PTT is holding the PC button assembly in

[DJ67]

12 minutes ago, RLCarter said:

Looks like the bracket for the PTT is holding the PC button assembly in

I wondered about that too, and I might give that a try today.

[Pasturepilot]

2 minutes ago, DJ67 said:

I wondered about that too, and I might give that a try today.

Yeah, those two screws look to be wedged against if not atop the lower housing for the button. 

The mistake I made (Mine was in there pretty tight as well) was prying against the lower housing of the button instead of the plastic part of the yoke. Photo of the button assembly attached (swiped from an eBay listing) to make sure you don't make my mistake. The whole thing comes out as a single assembly. I've heard people say pennies are the best prying device so you don't damage the button, and that's good advice. 

As long as you're less destructive than I was that day. 

 

Pop that bracket out of the way and see what happens. 

 

[Gary0747]

You can make all the right sized rubber band rings by cutting a small bicycle tube.

[Jerry 5TJ]

After 45 years the PC button on my C model failed.  

I removed the button assembly.  Then unscrewed the bottom from top to get at the internal spring, which had broken.  Installed a suitable replacement spring.  Cleaned out decades of gunk with alcohol.   Installed new O rings.    

AOK then. 

[brad]

When I bought my 75 F in 2001, Lone Star in San Antonio moved it to an on/ off toggle on the panel.  I turn it on, adjust the turn coordinator knob, then engage my Accutrak II.  Works beautifully - and I like hand flying with no PC on.

[DJ67]

On 7/9/2019 at 10:03 AM, Pasturepilot said:

Yeah, those two screws look to be wedged against if not atop the lower housing for the button. 

The mistake I made (Mine was in there pretty tight as well) was prying against the lower housing of the button instead of the plastic part of the yoke. Photo of the button assembly attached (swiped from an eBay listing) to make sure you don't make my mistake. The whole thing comes out as a single assembly. I've heard people say pennies are the best prying device so you don't damage the button, and that's good advice. 

As long as you're less destructive than I was that day. 

 

Pop that bracket out of the way and see what happens. 

 

Success!  Removing the PTT bracket gave me better access for prying.  I had earlier tried to separate the button from the housing and in the process lifted the housing a bit.  So I found myself prying the razor thin housing flange, and breaking some of it away.  Should have remembered to follow your advice about prying between the button and the yoke casting.

Anyway, the problem was corrosion between the button housing and the yoke.  I got it off with my thumbnail, so I can't wait to see if it slides back in where it was.

Thanks for the tips.

Doug

Edited July 10, 2019 by DJ67

[DJ67]

On 7/9/2019 at 10:26 AM, Jerry 5TJ said:

After 45 years the PC button on my C model failed.  

I removed the button assembly.  Then unscrewed the bottom from top to get at the internal spring, which had broken.  Installed a suitable replacement spring.  Cleaned out decades of gunk with alcohol.   Installed new O rings.    

AOK then. 

I hadn't realized that the bottom of the assembly was a nut!  I managed to get the whole thing out and cleaned up the corrosion that made it so hard to remove in the first place.  Already fitted new o-rings and ready to see if it slides back in.  I'm a tad concerned that the hole in the yoke is still corroded, so I'm planning a way to clean that too.

Thanks for the tip.

Doug

[carusoam]

Great pics DJ.

Best regards,

-a-

[corn_flake]

For the pennies method, I take it you would still pry the button while making sure the pennies is not in the way for the housing to come up?  Considering the thiness of the housing flange, I doubt it can take much force.  Also, pennies wouldn't fit under the flange anyway. 

 

On 7/9/2019 at 8:03 AM, Pasturepilot said:

Yeah, those two screws look to be wedged against if not atop the lower housing for the button. 

The mistake I made (Mine was in there pretty tight as well) was prying against the lower housing of the button instead of the plastic part of the yoke. Photo of the button assembly attached (swiped from an eBay listing) to make sure you don't make my mistake. The whole thing comes out as a single assembly. I've heard people say pennies are the best prying device so you don't damage the button, and that's good advice. 

As long as you're less destructive than I was that day. 

 

Pop that bracket out of the way and see what happens. 

 

 

 

[DJ67]

Well I got it back in.  Had a wooden kitchen spoon, and the handle had the exact OD to burnish the valve housing in the yoke.  So I feel like the corrosion is gone inside there now.   The unit slides in okay then acts like it has a detent at the bottom.  I can pull it with my finger and thumbnail, but it's really hard to get it started.

Now that I look at the picture I posted before, with the PTT on the left, I think I can get a rubber band on the handle part and then slide it up onto the button when I want to be my own wing leveler.  I might try it with the PTT cord under the rubber band.  It would be cleaner to remove the PTT and put two rubber bands (2nd one is a spare), and then re-install the PTT.

[Pasturepilot]

22 hours ago, corn_flake said:

For the pennies method, I take it you would still pry the button while making sure the pennies is not in the way for the housing to come up?  Considering the thiness of the housing flange, I doubt it can take much force.  Also, pennies wouldn't fit under the flange anyway. 

 

 

Yes. One penny against the plastic, to elevate the second penny and protect the plastic yoke. The second penny wedges between first penny and under the rim of the PC button. I'll try and remember to take a picture or video next time I'm with the plane. 

[eisn7311]

Any tips for removing a stuck button housing? My button came out and was lost. Either the nut at the bottom was unscrewed or it the threaded part broke. 

[carusoam]

Congrats on the first post Eisn.

This thread is mostly about parts stuck in the hole, and how best to get them out... Note the pic with the lightly corroded surface... and ancient O-rings...

 

Sounds like you may be needing another part...

We have some resources around here for that as well....

Best regards,

-a-

[corn_flake]

Thanks for the pennies advise.  I was able use four pennies with two on each side to add thickness.  Once the button is able to lift up the main housing, I was able to get one penny on each side of the "lip" pull it up all the way.