Tach failure

[lotsofgadgets]

Flying home from Sun-N-Fun yesterday and my Tach started to act up and failed completely.  Initially the RPM needle started bouncing from 2100 to 2600 RPM and progressively the range of bouncing expanded to 1500-2500.  Eventually the needle simply quit and showed 0.  The hour meter was continuing to increment, but at the end of the flight hobbs showed over 3hrs and tach was only 1.5.  Does anyone have any experience with this type of failure? 

Any suggestions on how to confirm it is the tach and not the cable?  It looks like 14 day lead from Spruce for a new one, anyone have a better source?

1982 M20J, IO-360 A3B6D.  

[ArtVandelay]

I have one from a 78J if interested:

[lotsofgadgets]

How much?

 

[ArtVandelay]

How much?
 

$25 + shipping you require

[Trailboss]

I had the other issue...Hour meter stopped but tach kept running.  Although more $$'s, I replaced it with a P-1000.  Very happy with the upgrade to digital and it gives independent mag RPM's so run-ups are easy and in-flight monitoring of each one is possible.

[carusoam]

About the failure...

Expect that the wire cable wore out or broke....  it’s like a speedometer cable from an old bicycle...

you could probably hear it when it would wind up and then release...

While it is doing the funky chicken... the tach is getting a bit ruffled...  

On my 65C, the cable was doing its thing and the tach bounced the needle off the peg... knocking the needle off.  

OH of the tach required pressing the needle back on.

Make sure you get the right length replacement cable.  Measure the old one...

Best regards,

-a-

[Cyril Gibb]

21 hours ago, Trailbossauction said:

I had the other issue...Hour meter stopped but tach kept running.  Although more $$'s, I replaced it with a P-1000.  Very happy with the upgrade to digital and it gives independent mag RPM's so run-ups are easy and in-flight monitoring of each one is possible.

+1

In addition, I like the green/red/yellow(restricted range) lights.  They catch your eye where a mechanical tach wouldn't.

[Bartman]

Sorry I cannot answer your question, but looks like a good reason to upgrade to the JPI EDM 900

[JaM20C]

Had same issue with my tac last year. Pulled old cable measured it and ordered new one and it is smooth as silk now. To make sure it wasn’t the tac I was able to rotate the tac and see it was working properly. This occurred after a some costly repairs and wasn’t in the position to upgrade to digital. Mechanical works just fine.

[carusoam]

Great first post Ja!

I enjoy people posting in agreement.  

Your liked post to ordinary post ratio is at a very high level of 1:1...  keep up the good work!

Best regards,

-a-

[gsxrpilot]

I lost a tach in my M20C on the way to Oshkosh a few years ago. Once there, I spoke with DMax about it. He said he wouldn't install OEM tach's and to get an EI R1 tach instead. It was still about 6 weeks from Aircraft Spruce.

[Steve W]

On 4/18/2018 at 9:58 AM, Bartman said:

Sorry I cannot answer your question, but looks like a good reason to upgrade to the JPI EDM 900

I have an EDM 900 on the way to get installed while the engine is off, but my current plan is to keep the stock EGT, Tach and MP just as a backup and so I don't have even more panel holes with filler plates. (This year, EDM 900, next year re-cut panel... maybe)

[gsxrpilot]

4 hours ago, Steve W said:

I have an EDM 900 on the way to get installed while the engine is off, but my current plan is to keep the stock EGT, Tach and MP just as a backup and so I don't have even more panel holes with filler plates. (This year, EDM 900, next year re-cut panel... maybe)

What??? Panel hole filler plates don't weigh nearly as much as plugging the holes with old gauges. I can tell you from my experience trying to hook up the EDM900 and the original gauges to the same probes/wires/sensors/etc... doesn't work anyway. 

I could probably send you the hole covers anyway... for cheap... do you want aluminum (unpainted) or black textured plastic?

Throw that tach in the bin and get the EDM-900 installed.  

 

[Marauder]

What??? Panel hole filler plates don't weigh nearly as much as plugging the holes with old gauges. I can tell you from my experience trying to hook up the EDM900 and the original gauges to the same probes/wires/sensors/etc... doesn't work anyway. 
I could probably send you the hole covers anyway... for cheap... do you want aluminum (unpainted) or black textured plastic?
Throw that tach in the bin and get the EDM-900 installed.  
 

I debated for a bit about keeping the factory gauges as redundant equipment. I decided to remove them do the “panel fillers”. Should have left them! Didn’t like the way the filler looked. Even with a few things stuck in the filler.





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[Steve W]

Just now, Marauder said:

 

I debated for a bit about keeping the factory gauges as redundant equipment. I decided to remove them do the “panel fillers”. Should have left them! Didn’t like the way the filler looked. Even with a few things stuck in the filler.

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That answers where the alert LED can go for now. The most important part is figuring out if I can match Mooney beige.

 

50 minutes ago, gsxrpilot said:

What??? Panel hole filler plates don't weigh nearly as much as plugging the holes with old gauges. I can tell you from my experience trying to hook up the EDM900 and the original gauges to the same probes/wires/sensors/etc... doesn't work anyway. 

I could probably send you the hole covers anyway... for cheap... do you want aluminum (unpainted) or black textured plastic?

Throw that tach in the bin and get the EDM-900 installed.  

 

Nah, not the cluster gauge, just the Tach MP and EGT. There is already an Insight and the factory EGT, so the EGT hole in the exhaust would have to be plugged(or the probe abandoned). The Tach doesn't look like it conflicts as far as sensor location, and the MP will just need a Tee.

Now, who knows, maybe next year those will get ripped out too.

[Marauder]

Nah, not the cluster gauge, just the Tach MP and EGT. There is already an Insight and the factory EGT, so the EGT hole in the exhaust would have to be plugged(or the probe abandoned). The Tach doesn't look like it conflicts as far as sensor location, and the MP will just need a Tee.
Now, who knows, maybe next year those will get ripped out too.

I have redundant MP, RPM and fuel pressure/flow. The only one that was a challenge was the fuel pressure. My mechanic installed a T to be able to use both the EI fuel totalizer and the JPI 900.

This leaves the only primary gauges dependent on the JPI to be the oil temp, oil pressure, fuel gauges, the one CHT and ammeter.




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[Mooney in Oz]

9 hours ago, Marauder said:

I have redundant MP, RPM and fuel pressure/flow.

That looks so neat.  Is the MP and RPM the same size as OEM's?

[Marauder]

That looks so neat.  Is the MP and RPM the same size as OEM's?

The EI units are 2.25” units. I think the modern Mooneys use the smaller size. The older Mooneys had 3.5” units. I had the right side panel remade to fit more breakers and to eliminate the need for hole adapters.




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[bradp]

Chris is the texture just the stuff the comes in the rattle can? 

[Marauder]

Chris is the texture just the stuff the comes in the rattle can? 

That picture was taken in early 2013. The stuff on the left is some sort of plastic that has the texture in it. The panel on the right is covered by the factory Naugahyde.


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[lotsofgadgets]

Update:

Turns out the problem was with the tach drive cable.  after removing both ends from the engine and gauge I noticed that the engine drive side was rounded and no longer engaging properly.  I am going with Trailboss's suggestion of the Horizon P1000 as a permanent fix.  I hanger neighbor has a used one he pulled from his Bonanza.  Hopefully Horizon is willing to work with me to get the necessary paperwork and reset the limits.  BTW, the tach drive covers are $90 from Lycoming, or $6 from Vans Aircraft.  

[carusoam]

Great follow-up, Lotso!

Best regards,

-a-

[Cyril Gibb]

On 4/23/2018 at 9:33 AM, lotsofgadgets said:

.  Hopefully Horizon is willing to work with me to get the necessary paperwork and reset the limits.  

The previous owner of Gladys installed a new prop with different rpm restrictions but just placarded the P1000.

Horizon updated the innards no problem, and not expensive. 

[lotsofgadgets]

For $250 they are reseting the unit for a 4cylinder and configuring the RPM ranges to match.  Sandy at Horizon was a pleasure to work with and she figures it will be about 2 days to turn it around.

[carusoam]

Great Pirep, Lotso!

Best regards,

-a-