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Tachometer Issue

ABS Full Member
Posts: 18

My cylinder AD replacement has just been completed, along with cam/lifter replacement. The shop tells me the tach isn't working and doesn't know if it is a sensor or the gauge. The continuity is good on the connections. They are going to put an oscilloscope to it tomorrow to find out what's what. It was working fine when I delivered the aircraft. Any suggestions?

Model: Bonanza A36TC
Posted 1/30/2017 - 3 years ago
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ABS Full Member
Posts: 184

We need your year, model & any engine mods to help much.

Many have replaced OEM tachs with new digital ones that read off P-leads

Posted 1/30/2017 - 3 years ago
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ABS Full Member
Posts: 18

1986 B36TC EA460. The tach is original. No mods to the engine, other than a fuel flow transducer which was installed 7 years ago.

Posted 1/31/2017 - 3 years ago
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ABS Full Member
Posts: 184

If they can troubleshoot the problem, great.
Don't pay for their learning curve though.
May be cheaper to replace with and STCd digital if they can't isolate the problem
(wiring, generator or gauge)

Posted 1/31/2017 - 3 years ago
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ABS Full Member
Posts: 18

Paul, would you have a make/model and or supplier for the digital tach and accessories? My guy is going to call Instruments Inc. to see about an overhaul. So far they think the sensor is the culprit. Replacement is apparently very expensive.

Posted 1/31/2017 - 3 years ago
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ABS Full Member
Posts: 184

I installed the Electronics Internation R-1 in a lower 2-1/4" hole so I could use the OEM tach hole for a JPI-830 engine monitor. It picks up off the P-leads at your mag switch, so no wires thru firewall (make sure to order cap for the tach generator at the engine if removing cable) They will program in the current airframe total time & your RPM redline. It only records chronological time above 1400rpm

The Horizon P-1000 is commonly used too, has a mag fault indication.

Posted 1/31/2017 - 3 years ago
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ABS Full Member
Posts: 18

Thanks for that. I will talk to the shop tomorrow regarding the R-1. It looks like the easiest route.

Posted 1/31/2017 - 3 years ago
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ABS Full Member
Posts: 33

I got oil in my tach, so I replaced it with digital one without issues. I do not remember the cost but for plane instruments I remember thinking it was less than I expected or a rebuilt tach. Be ready for a bit more apparent accuracy. Mine fluxuates 5 -10 rpm which you would not see on an analog gage. Also a red light appears at 2706 rpm on take off so I have to back my propeller one turn to keep from over speeding.

Posted 11/29/2017 - 2 years ago
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Tachometer Issue