Tachometer Output/Tach Dead?

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obxer
MegaSquirt Newbie
Posts: 27
Joined: Fri Aug 03, 2007 8:13 am
Location: Nags Head, NC USA
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Tachometer Output/Tach Dead?

Post by obxer »

Wasn't sure where to put this question -

What I've read says the uS tach output on pin 35 should drive most any tachometer. Does that include older tachs that tach their input straight off the negative side of the coil? Either I've blown mine out or the input isn't working for me. I've verified that the tach (older VDO) is getting power and ground and verified the connection from the input all the way through from PIN 35. What's next? I can scope the output from the uS - but what should it look like?

Suggestions? Or do I just buy a new tachometer?
Allen Massey

1988 Evante MK1 - http://www.obrox.com/evante
Matt Cramer
Super Squirter
Posts: 910
Joined: Sat Jul 03, 2004 11:35 am

Re: Tachometer Output/Tach Dead?

Post by Matt Cramer »

The tach output is supposed to be a 12 volt square wave. That should work with most tachs, but some that need a high voltage spike might not work with it.
Matt Cramer at DIY Autotune
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obxer
MegaSquirt Newbie
Posts: 27
Joined: Fri Aug 03, 2007 8:13 am
Location: Nags Head, NC USA
Contact:

Re: Tachometer Output/Tach Dead?

Post by obxer »

Thanks Matt. I've started checking into Tach Adapters. Maybe that will work for me.
Allen Massey

1988 Evante MK1 - http://www.obrox.com/evante
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