Yanmar tach problem

[hpeer]

After running for a few hours the tach will go to full scale and stay there.

Obviously the engine is no over revving.

Anyone else come across this issue and have a fix?

[mikepmtl]

I had an issue with it dying after a few minutes. I was lucky that all I had to do was just cleaned the 2 wires on the engine, fix the crimps a little and every thing was normal again.

The problem started right after I had the mixing elbow replaced. I don't have my service manual handy, but there is a complete procedure on how to diagnose it.

[impi]

Originally Posted by hpeer

After running for a few hours the tach will go to full scale and stay there.

Obviously the engine is no over revving.

Anyone else come across this issue and have a fix?

Yes and I still have this problem occasionally ... very irritating. I have cleaned all the terminals and sprayed water sealant lubricant to protect against moisture without any luck. I find that while the engine is running if I switch off the key momentarily and then back on without pressing the 'shutdown button' it sometimes sorts itself out'. As a rule I do not like to do this as it can damage the alternator to run the engine with the 'key off' position while the engine runs, however if done as a short on / off motion it is fine (so I am told).

I also had the problem where I could no longer see the hour meter readouts ... that came right all by itself and fortunately the hours do keep recording as per normal ...

I find this very frustrating and hope we have some one who has a decent answer for us!

[sailorchic34]

On mine, it was corrosion on the connectors also. Happens about once every few years for me. Clean the contacts and the problem goes away, for a while..

[laika]

Not an expert, but it sounds to me like it might be a bad ground. You could try wiring the tach ground directly to the engine ground and see if problem persists. You said you cleaned all the terminals, but if the wire is untinned as it was with my Yanmar, who knows.

Otherwise, it could always be something faulty behind the panel cluster, but I know that's awfully vague.

[hpeer]

My symptoms are more like impis post, although I did not go into details at first.

And yes, my Yanmar wire is not tinned.

Don't know how the tach works, but I assumed that it was integrating a pulsed signal from the alternator. Because it goes to full scale, that would be like getting 12 vdc on the lead, which would be strange.