 Jumpy tach |
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| mittelmotor |
 Jun 13 2012, 03:03 PM
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#1
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Member  Group: Members Posts: 334 Joined: 21-May 12 From: SoCal Member No.: 14,464 Region Association: None  |
My tachometer needle tends to jump around a lot, rather than swinging in a nice smooth arc. Any suggested fix? If others have experience here, I'd love to hear how you've fixed it.
Thanks! |
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Replies
| Valy |
Jun 14 2012, 12:44 PM
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#2
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Senior Member Group: Members Posts: 1,677 Joined: 6-April 10 From: Sunnyvale, CA Member No.: 11,573 Region Association: Northern California |
I had the same problem in the past.
I took a plot of the points voltage with my scope. The blue line is the actual voltage on the points and the red one is what you would like it to look like. The biggest problem is that the negative spikes near the pulse middle cause the tach to believe the engine is spinning faster than it realy does. Some spikes are dumped by the tach filtering circuit but some are too big for it to handle so you see the tach jumping up.  |
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Posts in this topic
mittelmotor Jumpy tach Jun 13 2012, 03:03 PM
brant do you still have points.
often its an ignition or... Jun 13 2012, 03:04 PM Black22 I've have the same problem. Seems to be very c... Jun 13 2012, 03:10 PM SirAndy Several years ago, i bought a (brand new) relay bo... Jun 13 2012, 03:15 PM mittelmotor Thanks! Car still has points. Now I have some ... Jun 13 2012, 03:25 PM
brant
Thanks! Car still has points. Now I have some... Jun 13 2012, 03:42 PM Series9
Thanks! Car still has points. Now I have som... Jun 14 2012, 09:13 AM Bartlett 914 You will find threads about changing capacitors in... Jun 13 2012, 04:03 PM 914Bryan There were a lot of ideas here, I just learned to ... Jun 13 2012, 07:03 PM sean_v8_914 always check teh cheap stuff first but...NH speedo... Jun 14 2012, 09:19 AM larss My tach got cured from jumping after fixing the ea... Jun 14 2012, 12:55 PM hedgehog what i found when i had that problem was a loose ... Jun 14 2012, 01:25 PM |
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