Posted by lance_ryley (lance_ryley@…>)
the previous owner installed a 165 Amp Silver Bullet brand
alternator. When I bought the boat, the previous owner told me that
the tach wasn’t working because it was incompatible with the
alternator. I’m looking at the back of the tach, and there is a
jumper for settings “4, 6, 8” and it is currently set to “8.”
Can someone tell me why I can’t run a connection from the field
output on the alternator to the tach? Does anyone have any manuals
about the tachometer? I’m trying to find something online,
but “Quality Controls” from 1978 isn’t cutting it. Any explanation
will be much appreciated. Dumbing it down for a non-electrician will
be appreciated even more.
Thanks,
Lance
Posted by Brian Guptil (sailordude@…>)
Lance;
Sounds like a
tach designed for spark ignition engines. That will not work on a diesel.
There are tachs made with alternator connections, though yours does not sound
like one of them. The field excitation on the alternator is a DC level
that is not directly related to RPM but changes
with demand for charging. If your alternator has a “tach”
output, then you can find an alternator driven tach.
Yanmars have a
sensor on the flywheel end of the engine, that sends pulses to the tach from
the teeth on the flywheel. It would use a Yanmar tach. The sensor
looks like an oil pressure thing that screws into the flywheel housing and has
2 wires connected to it.
Check the
alternator for an extra lead labeled tach. If so, then look for an
alternator driven tach. You will then need to calibrate the tach using
another measuring device.
Brian
\
Posted by lance_ryley (lance_ryley@…>)
Thanks Brian - I kind of figured this might be the issue. The Silver
Bullet does have a field output for the tach. Not sure why the
original Perkins tachometer doesn’t work with it, but in the overall
scheme of things, the tachometer is relatively low cost. I
appreciate the information.
Lance
— In freedomyachts2003@yahoogroups.com, “Brian Guptil”
<sailordude@b…> wrote:
Lance;
Sounds like a tach designed for spark ignition engines. That will
not work
on a diesel. There are tachs made with alternator connections,
though yours
does not sound like one of them. The field excitation on the
alternator is
a DC level that is not directly related to RPM but changes with
demand for
charging. If your alternator has a “tach” output, then you can
find an
alternator driven tach.
Yanmars have a sensor on the flywheel end of the engine, that
sends pulses
to the tach from the teeth on the flywheel. It would use a Yanmar
tach.
The sensor looks like an oil pressure thing that screws into the
flywheel
housing and has 2 wires connected to it.
Check the alternator for an extra lead labeled tach. If so, then
look for
an alternator driven tach. You will then need to calibrate the
tach using
another measuring device.
Brian