My tachometer is the 2 in one tach with the "R" and "L" needles over each other. When I purchased the plane the left needle is always jumping around while flying. Sooooo the other day I pulled the left cable out of the conduit and cleaned it. It was somewhat gummy while removing it. I cleaned it in 100LL it looked like new after that. Then took some white lube in a can and sealed of the tach end and ran about half the can thru the conduit. On the other end I was catching all of the left overs in a can while spraying. Re lubed the cable while running it back thru the conduit and sealed it up. Took it for a flight today and it is still jumping. I guess the last thing to do is have the tach rebuilt itself. Anyone have some input?

I'm not an A&P but do the work under his supervision.

George: Just to be sure it indeed is the tach, and it sounds like it is, before
overhauling it, switch the cables from the right to the left and vice versa. If the jittery side
switches needles then the tach is ok, otherwise you have confirmed your suspicion and it is the tach that is the problem.

Gary

George,

Can't really say what the problem might be. Here are some ideas.

Could be the gauge needs work. If the plane has been sitting, the gauge might be sticky. Cable could still be a problem.

On the other hand, you may also wish to check the dome pressure.

If you have someone to fly with you and you have a strobe - you can strobe the prop and see if the prop stays steady and that would help isolate whether it is the prop or the gauge.

Hope this helps.

If the prop stays in synch, is it certainly not the prop. It might still by the cable is there is a strand broken that is hanging up. It might also be the gauge. I would do as Gary recommends before deciding to the the gauge overhauled. If it is the gauge, I would send it to Airparts of Lock Haven as they specialize in the old Piper stuff.

 

The last time I had a problem with the tach, I removed it from the aircraft and took it to the local automotive shop for testing on their speedometer tester. It tested out OK. The problem was elsewhere (and more expensive), but I was easily able to eliminate the tach from the equation.

Hank
Henry A. Spellman

does anyone have a dual elecritial tachometer gage and drive for insatllation/stc for a pa-30 that has a dual mechanical tach?

JPI..about $15K to $20K installed.

Just as a follow up I had the original Tach rebuilt, the bouncing has stopped It has never operated as smooth. Air Parts of Lock Haven did the rebuild and they did a quick turn around. g

George, thanks for posting the outcome.

I've always found Air Parts to do good work at reasonable prices. If you are comfortable, would you share the cost of the repair.

If our gauge goes, I'd like to understand this pricing vs new electronic tachs.

Iv'e just been down this road. My cable was the culprit. The ends can be re-done to take out any wear by an auto speedometer shop.The cable flexes in the engine tach drive or the instrument because one of the ends is worn and not "square". $80 per cable, tell them it's for a boat.bernie