Tach

I have a Van's tach installed. On my last flight the indication began to sputter occasionally and finally by the end of the flight it had gone to zero and stayed there. Is there an easy way to trouble-shoot whether it's the sender or the gauge? I have already checked the security of the connections.

Do you have a vacuum pump?

If so, check the cable that's used to attach the remote sender. Ours had a little 'tab' that fit in the tach drive. That tab broke off, so the cable wasn't turning. Sometimes the sending units go belly up but double check the cable or the end of the sending unit, if it's attached directly to the engine.

Best,

The sender on the tach is just a small generator.

Try manually spinning the sender with a drill. If the tach shows a reading, there is a mechanical problem between the cable/sender and engine.

If the tach shows 0 rpm when spinning the sendor, put a multi-meter on the leads going to the tach. If the multi-meter shows zero volts, the problem is the sender. If the multi-meter shows voltage your tach guage is faulty. I hope that makes sense. Good luck.

got a good ground on the sender?

I had problems with mine for a while,.. finally sorted out.

Mine did the same thing at approx 100 hrs, it was the generator. The replaceable stem that spins inside the device is most likely to long. I ordered three from vans and none were the same length, all were 1/8" to 3/8" to long. Being to long pushes the drive wheel back against the generator housing causing friction and eventual failure(internal). A small straight edge on the back of the generator housing showed an 1/8" crown this had created on my defective one(external).

I calculated how long the stem should be and ground it down when I replaced the bad generator with the new generator. No problems since.

I have the dimension of the stem and the old disected generator I could take a photo of at the hanger if you need it.

doug
9A-160 hrs