Squirrelly tach take 2

[roach]

Thanks ineedacottage and silver for your help but i 'm not 100% sure whats
wrong yet.
97 90 hp Johnson 90 CV non-oil injected.

1. Tach never does go to zero even when you turn the motor off
2. Forgot to mention friend recommended to take - battery cable off when
idling at house (with water hooked up of course ) to see if stator was
charging enough to keep it running , which it did. Did this damage the
tach ?
3. Did the Joe Reeves test and the tach failed. But I don't have a water
cooled rectifier.
4. Used a Johnson service manual
Stator test OK
Rectifier Ohmeter test OK
Tachometer Circuit test- I got to the part about checking voltage with the
engine running at 1000 rpms and disconnecting the tach and observing
the voltage increase ( which it did but only about 1/2 volt ) on the
instrument gray lead. I don't have a VRO pump so no test there.

I'm pretty sure I have a 6amp unregulated charging system .Also I have a
system check engine moniter tachometer

Thanks Roach

 

[F_R]

Re: Squirrelly tach take 2

First, that was bum advice about taking the battery cable off a running motor. That is almost guaranteed to blow the alternator rectifier, resulting in loss of charging and the tach won't work. You say your rectifier tests OK, are you sure? Re-test your rectifier if no good, replace it. The tach may then work too.

Very many tachs do not go to zero when turned off. But they should read the correct RPM when running.

 

[rndn]

Re: Squirrelly tach take 2

My tach does not go to zero once I shut it down either. It does read the correct RPM's when running.

 

[Barnacle_Bill]

Re: Squirrelly tach take 2

Most tachs I've seen will go to zero with the key on and motor not running.

 

[roach]

Re: Squirrelly tach take 2

imported fr checked the rectifier again.
Checked on the R x1000 scale
yellow to ground ,8000 ohms, reverse infinite
yellow/gray to ground, 8000 ohms, reverse infinite
yellow to red, 8000 ohms,reverse infinite
yellow/gray to red,8000 ohms,reverse infinite

Talked to dealer said they would loan me a used tach to check mine.
Don't get much better than that.

Thanks roach