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Discussion Starter #1
Recently my tack has started acting up. It will be at 0 at idle then jump to 6K and stay there regardless of actual RPM. When goes back to idle, back to 0. Then it straightens out after a few minutes and it's fine again. Is the tach on this thing electronically controlled or is it gear driven?
 

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Old Wizard
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Erratic Tach

Electronic tachometers give erratic readings when the base voltage is low, usually caused by a loose battery connection. The worse situation for low voltage is at idle when the alternator output is at it’s lowest. You may just need a new battery or a good charging.

If it's not the battery:

Most likely - Intermittent power or ground connection
Next likely - Intermittent rpm signal connection
Least likely - Tachometer internal problems

Check for a loose or corroded electrical connection at the battery, the fuse, and any in-line connector. Check the two battery connections first, next the connector at the instrument cluster, then at the fuse, and lastly at the wiring harness connections.

Next, since the bike is running OK, the RPM sensor gap, the sensor itself, and wiring back to the computer are not the problem. So you need to check the connectors between the computer and the tach.

Finally, try to borrow a tach to verify that it’s actually the problem, before buying a replacement.
 

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Premium Member
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Everything Shaz said but do one thing first after checking the battery...check the three brass screws on the back of the tach. They ground the circuit board inside and often vibrate loose. Simple and the most COMMON problem, besides the resistor inside on the circuit board coming loose.
 

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Discussion Starter #4
Thanks for the info guys, I have some time today so I'll check that out. My temp gauge is behaving odd too so It may be a similar issue. Would have done something sooner, but had a 350 mi ride yesterday and didn't want to mess anything up prior.
 
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