Tachometer Only Reads to 1600rpm !

[Divertitch]

I have a problem with my tacho. Its attached to the correct termial of my alt but it reads up to 1600 even when the engine is only doing less revs. Tacho head is new and the fault was the same with the old one. Output is normal 35amps 12v no overheating. Just can not see the number of revs the engine is doing!

[r.furborough]

tachometers need to be calibrated to the alternator output pulses. There should be instructions on the method of calibration or settings that are specific to the make and type of alternator used.

[RobCole43]

Being very new in this forum, I hope this is the correct way to add my problem, which is similar in a way. I have a Bukh 36 diesel onboard and an Amplepower regulator system My Tachometer is connected to the W terminal, but due to the actions of the Amplepower equipment, does not give a correct reading.
The Tachometer even with the throttle all the way down (should be3600+ revs) only shows 1200. Any suggestions. The Bukh engineer said have a pulse wire fitted to your alternator, but is that not the same as the W terminal output?

[never monday]

Originally Posted by RobCole43

Being very new in this forum, I hope this is the correct way to add my problem, which is similar in a way. I have a Bukh 36 diesel onboard and an Amplepower regulator system My Tachometer is connected to the W terminal, but due to the actions of the Amplepower equipment, does not give a correct reading.
The Tachometer even with the throttle all the way down (should be3600+ revs) only shows 1200. Any suggestions. The Bukh engineer said have a pulse wire fitted to your alternator, but is that not the same as the W terminal output?

the AmplePower regulator should have a tach terminal

[GordMay]

Ample Power on “Tachometer Pickup”:

"... Because the alternator's prime function is to charge and maintain batteries, and because some regulators can actually provide a full charge, loss of tach signals is a given ...the regulator favors the battery. No one wants a boiling battery just so the tachometer reads properly.

Virtually all diesel engines have a port which will accept an RPM sensor. This mechanism produces a reliable tach signal without regard to battery state of charge. The RPM sensor does not suffer from belt slippage, and continues to operate even if the alternator has failed. We strongly recommend RPM pickups rather than using a signal from the alternator..."

Here ➥ Alternator Tachometer Signals

Rick on External regulators and tach drive

"Any external 3-step regulator will not allow the alternator to seamlessly drive a tach without problems when transiting to float and sometimes when in float.

One solution in design would require that the regulator monitor the tach output from the alternator as feedback to control some minimum drive while slowly transiting to a lower float voltage (less voltage means less alternator excitation and hence less tach drive voltage). Even then there will be some problems with some tachs which may require higher drive voltage. Regardless, no product exists that does this in a seamless manner for all tachs."

Post #11➥ http://www.cruisersforum.com/forums/...ator-7620.html

[S/V Antares]

There are many brands. Most Alt. Tachs have rotary or DlP switches to change the calibraton as pully sizes or number of poles (2-4-6 12). Can you gve us the brand and model # or a pcture of the back?

You will need someone with a photo tack to calbrate it when you figure out how.

[RobCole43]

Thanks Guys,
GordMay found the same answers as I did on the Ample Power alternator and unfortunately the Bukh 36 diesel does not have and RPM sensor pick up point.
Can someone please answer my last question: " Is the Pulse wire and W terminal the same?"
Thanks again.
Rob