The International Cessna^® 170 Association

Engine tach became inoperative and I found that the cable was broken about 1 inch from the end that goes into the engine drive. Also found that the cause of the broken cable was that the tach seized up.
1) I would like to order just the flexible cable, if possible. Are these custom made, or are they off-the-shelf parts?
2) The end that inserts into the tach is a square drive, like I am accustomed to seeing on automobiles. But the end that inserts into the engine drive appears to be a pressed on type of fitting with a tang on it. Is this a normal type of tach cable?
3) Any recommendations on where to send the tach for repairs? Right now, it is a toss up between Century Instruments and Aircraft Quality Instruments.

These people do all old and new instrument repairs.
http://www.keystoneinstruments.com/

http://www.airpartsoflockhaven.com/

Cables I have made at a local automotive speedometer shop.

John Hess

I have used Century Instruments

Thachometers are one of the most reasonably priced instruments in the panel. In fact, I’d wager that the cost of a new one isn’t very much more expensive than a repair. Personally, I wouldn’t bother with having one repaired. I bought a new Mitchell in 2006, and it is still rock steady and looks like new. See this thread for details.

You can replace the inner (twisted) drive cable and retain the outer sheath if you so-desire.... but WHY?
It really isn't much trouble at all to replace the complete assembly and you can relax knowing the outer sheath is also new...and less likely to have rough innards that may shorten the life of your inner drive cable.

Pull out the entire cable sheath and all.... measure the length... call Aircraft Spruce (or any other supplier) and get a new assembly virtually overnight and install it. It's the best way to do it, IMO, and avoid the piecemeal installation.

Or, avoid all the potential troubles with the old cable/tach and install an electronic tach that has no firewall penetration, no oil leak potential, and is accurate at all rpm.

I am with you on this one Richard .i fitted a EI electronic tachometer and it’s other bells and whistles makes a good unit. The only sticky point is the resistors that you have to play with due to different mags fitted and the end cap over the old tach drive housing. That was only 15 dollars [end cap ]. Spruce has them. But in the end a great toy to play with. And very accurate . No more oil leaks or noise .

Share tach experience

Sudden great squawking sound, Hades sound. Glad I was on the ground. Bad tach is disturbing.

Told local FBO to replace with a new unit. He did. Got what I wanted, new tach.

It was totally inaccurate. We tested it . Just not satisfactory. Get that china mfg out of my panel!

I can't get no satisfaction - And I tried -- and I tried .... Cause I tried..
How White my Shirts could be..

Mick, fans are pulling for you Hope the surgery goes well in the AM tomorrow NYC>

Shipped tach off to Century Instruments. Awaiting response from them if able to be overhauled or not. Would like to keep this tach, if at all possible. Will be going George's route of pulling entire cable/sheath assembly and replacing with new. Thanks to everyone for their input/suggestions. Will post an update on progress.

I get it that some folks like the "digital" tachometers... but I didn't care for the "dancing" numerals and found them distracting. They may be accurate...but they are TOO accurate (sensitive) in my experience. Flying along in cruise results in dancing numerals … entering/exiting clouds will show a change due to air density..same thing with turbulence.... And selecting a power setting becomes an excersize in fine-tuning the throttle when all I wanted was approx. 1700 in the pattern or 2450 in cruise, etc. 1713 didn't work for me and 2439 ..2430... 2442... 2438.... didn't either. The 60 year old analog works just fine and gets my head back out of the cockpit. (And it's not true that there's no "through the firewall"... there's an electric cable...and an oil leak at the disabled tach drive will be unnoticed in flight...not necessarily a good thing, sort of like the oil pressure copper line. Just my opinion...

My EI tachometer has a green outer lights which is a quick reference of engines RPM and if exceeded RPM there is a caution lights and the very bright red lights . Then in the center of the gauge there is the digital readout in 10 rpm increments. When flying I adjust the engine rpm using the green lights and use the digital display for fine tuning . There is a tach timer also showing time of engine run time above 1300rpm. I just love my toys in the cockpit. Due to having different toys [cockpit instruments ] I have decreased my fuel usage and run my engine at peak efficiency and navigation is so much easier
And accurate . . One big issue I have is after take off and leveling off to exit the circuit I am often run into red line on the engine and having the these bright red lights really get my attention

I fly with a tach checker on the glare shied all the time. Don't look at the mech tach.

ghostflyer wrote:.... . One big issue I have is after take off and leveling off to exit the circuit I am often run into red line on the engine and having the these bright red lights really get my attention

I admit it. I monitor my old style instruments and don't need red lights to warn me I've exceeded red-line. Hell.... I suspect that either my old O-300 or my old analog tach won't turn that fast within the ordinary operating airspeeds of this airplane.

If I had a highly-modified airframe/engine' combination perhaps it might benefit with digital upgrades... but then, I think I'd miss out on the reason I have an old round-tail airplane.

I tired of tach inaccuracies, cable issues, leaking cable gaskets, ruined tachs due to the gasket failure, etc. so upon my IA's suggestion, I purchased a Horizon P-1000 electronic tach in 2008. While pricey ($565) it solved those issues. At first I wasn't too happy with the fluctuations in the engine speed read outs, but after a short time it became a non issue. It also warns of overspeed, as mentioned above and if a mag isn't operating it alerts me. Mine came with a cap for the tach drive and so far hasn't leaked. Wish I could say the same for other areas of leaks on my O-300.

Share my Tach experience cont..

Told FBO - IA AP get that China tach out of panel, keep the money, keep the new tach as a souvenir.

Reinstall my original tach that you removed. He did.

Old tach now worked perfectly.

Difference; he greased the tach cable with VASELINE. It was just dry after 2500 hours.

There was nothing wrong or defective with orig tach.

I got satisfaction.