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Old 06-10-2012, 06:36   #1
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Tachometer Readings

I have installed a new tachometer, and it seems that it is reading less than it should. I also just installed new alternator. Is it possible that due to different pulley size on alt. that the tach would be off? The pulley is in fact larger than original.
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Old 06-10-2012, 06:45   #2
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Re: Tachometer Readings

the tach should have dip switches that will allow you to adjust the output for various pulses per rotation.
but yes, the pulley will affect the alternator speed, decreasing the number of pulses sent to the tach.
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Old 06-10-2012, 07:06   #3
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Re: Tachometer Readings

Our tachs (Faria) have two adjutsment mechanisms, one for gross adjustment, one for fine.

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Old 06-10-2012, 08:36   #4
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Re: Tachometer Readings

I had a similar problem on a yacht a few years ago.
One difficulty is knowing the correct revs.
Rather than get an optical tach to try and calibrate things, one of these seemed a better option.

It uses the pulses on the injector line.so it does not need the alternator. It can be left in place as backup.

Design Technology, Inc., Home of the Tiny-Tach - Diesel Tiny-Tach Tachometer
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Old 06-10-2012, 09:25   #5
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Re: Tachometer Readings

Can you borrow, or rent a hand-held mechanical tach that you hold against the crankshaft center. That way, knowing your pulley ratios, you can determine your tach speed .v. alternator output.
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Old 07-10-2012, 01:07   #6
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Re: Tachometer Readings

Quote:
Originally Posted by noelex 77 View Post
I had a similar problem on a yacht a few years ago.
One difficulty is knowing the correct revs.
Rather than get an optical tach to try and calibrate things, one of these seemed a better option.

It uses the pulses on the injector line.so it does not need the alternator. It can be left in place as backup.

Design Technology, Inc., Home of the Tiny-Tach - Diesel Tiny-Tach Tachometer
Wow Nolex, that's really neat! Neverhad heard of that methodology, and it sounds fairly foolproof... and cheaper than most aftermarket tachs, too.

Good one!

Cheers,

Jim
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