RDuplechin

M20E Instrument Cluster issue

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I’ve got 2 issues with my 65 M20E that are possibly related.  First, my left fuel sending unit was seeping and my A&P resealed it.  Since the repair my fuel gauge is stuck at about 1/4 tank indication.  Is there something that the A&P could have done to cause this or is it possible that this is a coincidence?

My A&P also added LED Nav Strobes and an electric step STC.  Since then 5 of the 6 gauges (L & R fuel, CHT, Ammeter, Oil Temp) in my cluster 22-166-09 have twitchy flickering needles.  Is there a common power supply or common ground  that could account for these bouncing needles?  I’m wondering if there is something the A&P could have done while running wires and installing switches in the panel that could account for the issue with the cluster...or is it another coincidence?  I’m not big on coincidence and now I’m being asked to believe in two.

Thoughts?   Thanks.

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They may be related to work done.  If the sender was removed, it may have been reinstalled and somehow gotten stuck.  Alternately, it could be the wiring on the sender.  Would double check that the ground is properly grounded at the sender and the signal is not somehow partially shorted simulating a stuck sender.  Can’t recall the resistance, but it is rather small.

Regarding the engine indications, it sounds like the strobe may be affecting the instruments.  It would be important to know if the ground was brought all the way back to the panel or if they were grounded in the wing.  It could be as simple as the power of the strobes is on the same breaker as the gauges.  Best practice would provide some electrical isolation.  Another thing to look at is to be sure the gauges ground is solid.  If loose, it could also cause similar symptoms.

Can’t recall if you said the power to the step was tied to the strobes, beacon or if you did something else.  Depending on the type of strobe, some are more noisy than others.  Even with LED, some Manufacturers have a switched power supply which is noisier.  

oh, does the flicker go away when you turn the strobes off?

Feel free to call or email and I’ll see if we can help you sort this out.  Hope the step is working well otherwise.

Rob

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I would highly doubt LED strobes would cause any noise issues. I wonder if something got bumped, or scraped, or the cluster gauge ground is compromised??

Only educated guesses, I am, ATP not A&P, with some EE back in the day...

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Hi Rob,

Thanks for the reply.  I had an extra switch and extra space so I had him give the step its own switch.  I’m not sure how he grounded the strobes but I will ask him.  I didn’t think to try the strobes off to see if I still have the bouncing needles...but I will try that tomorrow.   It’s a Whelan LED Nav/Strobe.  I have the Nav and Strobe on seperate switches since my Tail Beacon ADS-B is in the Nav.  I think all of that is isolated from the gauge cluster but I’m not certain of that.  

The step works great coming down...I’m still working on the up.  It sticks about 5 inches from the full up.  I used the Tri-flow you suggested and it is smoother.  I’m planning on pulling the step completely out to ensure nothing is burred or bent on the step shaft or the channel it slides in.  More to follow.

Thanks,

Rick

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Just now, Immelman said:

I would highly doubt LED strobes would cause any noise issues. I wonder if something got bumped, or scraped, or the cluster gauge ground is compromised??

Only educated guesses, I am, ATP not A&P, with some EE back in the day...

Intuitively, I would agree, but I am familiar with a couple that are quite noisy.  The beacon in my plane is one of them and I have run into issues at work too with same brand.  It is particularly bad when colder.  They happen to switch the power supply on and off, vs the output, so it is not the LED, rather the internal voltage regulator.  

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6 minutes ago, Immelman said:

I would highly doubt LED strobes would cause any noise issues. I wonder if something got bumped, or scraped, or the cluster gauge ground is compromised??

Only educated guesses, I am, ATP not A&P, with some EE back in the day...

I put a set of the Whelens on my airplane last year and can hear them in my com2.    Took me a while to figure out what the new beeping was.   :(

 

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1 minute ago, RDuplechin said:

Hi Rob,

Thanks for the reply.  I had an extra switch and extra space so I had him give the step its own switch.  I’m not sure how he grounded the strobes but I will ask him.  I didn’t think to try the strobes off to see if I still have the bouncing needles...but I will try that tomorrow.   It’s a Whelan LED Nav/Strobe.  I have the Nav and Strobe on seperate switches since my Tail Beacon ADS-B is in the Nav.  I think all of that is isolated from the gauge cluster but I’m not certain of that.  

The step works great coming down...I’m still working on the up.  It sticks about 5 inches from the full up.  I used the Tri-flow you suggested and it is smoother.  I’m planning on pulling the step completely out to ensure nothing is burred or bent on the step shaft or the channel it slides in.  More to follow.

Thanks,

Rick

Whelan tends to be pretty good.  Switching them off will tell you a lot.  If related, next step is to determine if it is ground or power.  
Regarding the step, does it “pop” through the rough spot or does it get stuck there?  The spring should absorb some roughness and pop through, but best for it to be smooth through the full range.

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1 minute ago, EricJ said:

I put a set of the Whelens on my airplane last year and can hear them in my com2.    Took me a while to figure out what the new beeping was.   :(

 

It could be a matter of moving the ground or power around.  Our Mooneys have a lot going on in tight quarters....  older audio systems sometimes were not installed in an optimal way with regards to grounds and shields as well.

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Robert regarding the step it is a hard stick about 5 inches from full up.  The motor eventually stops running.  Slapping or jiggling the step doesn’t do it.  A gentle pull from above or kick from below gets it moving the rest of the way.

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8 minutes ago, RDuplechin said:

Robert regarding the step it is a hard stick about 5 inches from full up.  The motor eventually stops running.  Slapping or jiggling the step doesn’t do it.  A gentle pull from above or kick from below gets it moving the rest of the way.

Ok, let us know what you find.  Best not to have the actuator bind for an extended period.  If you have pictures of the install, feel free to send to my email and maybe I can see something that would cause the binding.  The cable should be in line with the step shaft, but if for some reason the attach point is different on yours, I wonder if that is causing some binding.  

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RD,

The seal for the fuel level sensor is a simple piece of rubber...

Putting in on, requires handling the whole float device...

Checking why it is stuck is more normal psychology of the old system... 50 year old fuel level gauges...

 

While working on the step... check anything related to the old step.  Any old grease in there may have turned into a rock... a good cleaning may be very helpful... grease and dirt may have not blended very well...

 

PP thoughts only, not a mechanic... my M20C didn’t get a fancy electric step... :)

Best regards,

-a-

 

 

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1 hour ago, takair said:

Intuitively, I would agree, but I am familiar with a couple that are quite noisy. 

Wow, ok, well I learned something new today!

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Proper grounding.   I believe Mooney ran ground wires to lights and everything in the wings and tail instead of relying on frame ground.

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Rob here is an update.  The nav and strobes are independently grounded in the wing.  I ran it up today and the gauges were rock steady...not a flicker.  I love intermittent electrical gremlins.  

 

I pulled the step completely out. I scraped off 55 years of varnish and crud.  It is better but still sticks.  After further analysis I really think the upper attaching point needs to move up just a little.  It appears to pull the strut into a bind at the very top of travel.  I didn’t notice it before.

 

More to follow after I do that...thanks.

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1 minute ago, RDuplechin said:

Rob here is an update.  The nav and strobes are independently grounded in the wing.  I ran it up today and the gauges were rock steady...not a flicker.  I love intermittent electrical gremlins.  

 

I pulled the step completely out. I scraped off 55 years of varnish and crud.  It is better but still sticks.  After further analysis I really think the upper attaching point needs to move up just a little.  It appears to pull the strut into a bind at the very top of travel.  I didn’t notice it before.

 

More to follow after I do that...thanks.

Thanks Rick...intermittent is no fun!

The geometry of the actuator should be fairly well fixed because the holes that align it are from the Mooney jig.  If you have a picture of the install, I may be able to zoom in on the problem area....but I think you are getting close.  Alternately there is some stuff on line I can pint you to.  If you have the addendum I include, that may help as well...I can always email a copy,

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I have a video of operation both up and down I can send you.  The reason I’m keying in on the geometry is that with the cable disconnected the step is so free it falls out and can easily be pushed all the way up with one finger.  With the cable attached it binds the last 6 inches going up.  It is a slight bind that isn’t there with the cable unattached.  Send me your e-mail and I’ll send you the videos if you like.

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10 minutes ago, RDuplechin said:

I have a video of operation both up and down I can send you.  The reason I’m keying in on the geometry is that with the cable disconnected the step is so free it falls out and can easily be pushed all the way up with one finger.  With the cable attached it binds the last 6 inches going up.  It is a slight bind that isn’t there with the cable unattached.  Send me your e-mail and I’ll send you the videos if you like.

That would be great.  Email is flightenhancements@yahoo.com

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10 hours ago, RDuplechin said:

I have a video of operation both up and down I can send you.  The reason I’m keying in on the geometry is that with the cable disconnected the step is so free it falls out and can easily be pushed all the way up with one finger.  With the cable attached it binds the last 6 inches going up.  It is a slight bind that isn’t there with the cable unattached.  Send me your e-mail and I’ll send you the videos if you like.

Thanks for the videos.  I found a couple of things to look at.  I sent a couple of emails...they sometimes end up in spam.  Feel free to call if you have questions.  Rob

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