The Cessna 120-140 Association Forum

The tach pointer on the 120 is wobbling up and down more than it used to. Where would the gurus start to isolate the cause? New tach cable?

Assuming that it is a mechanical cable going from the engine to the instrument.

I would clean and lube the inner drive cable.

Rick

Yes it is mechanical, and I will start with your suggestion.

What is the suggested procedure to Clean & Lube a tach cable ?? In the end, would it just be easier to replace with a new tack cable? A/C Spruce shows @ $40 -$50 dollars. But will have to re- Confirm if the C-85 Tack Cable is Left or Right Lay, I have forgotten. Br, Mike

I have to remove a mag in order to more easily get the sheath unscrewed from the accessory housing. Disconnecting the sheath from the tach from under the panel is easy. I pull several very small pieces of cut up gun cleaning patches thru the sheathing with some safety wire, patches soaked in solvent of your choice, (watch out for dripping solvent in the cockpit) then clean the actual tach cable with solvent and lubricate with lithium grease, lubriplate, moly grease, it seems all my A&P's have a preference and proceedure. I pull a few patches with grease thru the sheathing also. I keep the cable in the same direction as removed of course. Fit it into the engine side first, it's easier to final connect at the tach.

Thanks for the details. Debating a clean up, a new cable, or installing an EI electronic tach and being done with it all.

I decided on the middle choice. Less messy and not expensive. Ordered a new cable.
Regardless of the choice, just don't accidently bump the prop when the Mag off getting to the Tach Drive Housing.
You'll have to reset the timing. Clear Skies - Mike

I'd be interested to know. For me over the years...........7 times out of 10 the tach gauge is the issue.

Went for the EI R1 electronic tach - no more cable. Put one recently in the 210 and it works great. Now the tach time and the TT aircraft will be the same again.