JimC
Well-known member
Does anyone know whereabouts on the Hitachi alternator fitted to Yanmar engines one attaches the pulse wire to drive an electronic tachometer or rev counter.
Taking tachometer signal from alternator
- Thread starter JimC
- Start date
VicS
Well-known member
A bit of a delve into the Yanmar manuals reveals that some take a signal from a sensor that senses the passing teeth of the starter ring gear , not from the alternator at all. G and W terminals of the tacho
others do take a signal from an 'R' terminal of the alternator. The R terminal when it exists is a connection to just one of the main stator windings. No idea if that was referring to a Hitachi alternator. On some makes it is identified as the 'W' terminal.
If the tacho requires a signal from the alternator then you are looking for a connection to one of the stator windings. If the alternator does not have such a connection it may be possible to add one.
Sorry not much help but if you give the engine type and the alternator model maybe someone will have the info.
others do take a signal from an 'R' terminal of the alternator. The R terminal when it exists is a connection to just one of the main stator windings. No idea if that was referring to a Hitachi alternator. On some makes it is identified as the 'W' terminal.
If the tacho requires a signal from the alternator then you are looking for a connection to one of the stator windings. If the alternator does not have such a connection it may be possible to add one.
Sorry not much help but if you give the engine type and the alternator model maybe someone will have the info.
William_H
Well-known member
Alternator tacho sensor
As I understand Vic the sensor wire comes from the centre of the star connected 3 phase output before the rectifier. The voltage here then is something like 7 volts with 6 pulses per revolution. If it were connected to one leg of the 3 phase before the diode you would get one pos and one neg per revolution at about 18volts peak. Have I got it wrong or are there different ways of doing it.
My old Ford 1982 had a connection to the centre which fed to a heater on the temp sensor of the carb autochoke. So some power can be sucked out. The heater was to get the choke off faster than the inherent rise of temp of the carb itself. Other systems have had a light connected to the centre connection to show alternator charging. (light on normal) olewill
As I understand Vic the sensor wire comes from the centre of the star connected 3 phase output before the rectifier. The voltage here then is something like 7 volts with 6 pulses per revolution. If it were connected to one leg of the 3 phase before the diode you would get one pos and one neg per revolution at about 18volts peak. Have I got it wrong or are there different ways of doing it.
My old Ford 1982 had a connection to the centre which fed to a heater on the temp sensor of the carb autochoke. So some power can be sucked out. The heater was to get the choke off faster than the inherent rise of temp of the carb itself. Other systems have had a light connected to the centre connection to show alternator charging. (light on normal) olewill
misterg
Active member
If it's the one fitted to GM series engines there isn't anywhere to connect a tacho.
Yanmar tacho works from an inductive sensor near the flywheel. Alternatively look up 'Tiny Tach' which picks up RPM from pulses in the injector pipe.
HTH
Andy
MrCramp
Active member
I had a 2GM20 and took the Hitachi alternator to the local commercial vehicle electrical company, who was a Lucas dealer and is an Eberspacher dealer. They also fit tachos and are diesel injection and pump engineers.
One of their chaps fitted me a suitable wire connected to the correct winding so I could run a VDO (?) tacho. As has been said, the alternator doesn't have a suitable external connection.
cliffordpope
New member
I fitted one to the Hitachi alternator on a IGM10, so it can be done.
You need to open up the alternator and identify one of the stator winding connections NOT forming one of the outputs, and solder on a wire.
I can't remember any more detail than that, but I got it all by searching with Google.
You need to open up the alternator and identify one of the stator winding connections NOT forming one of the outputs, and solder on a wire.
I can't remember any more detail than that, but I got it all by searching with Google.
fireball
New member
We did the same thing - except took the alternator to an alternator specialist (as he was local) - he added the tacho output wire for a small charge and we added our own tacho from there.
