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Old 10-26-2003, 10:13 PM
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Why no Tach Readings?

I'm a bit peaved today . I recently bought a tachometer and wired it up to spec, and it doesn't work. OK so maybe I should return it?

No, not today! I hook up my dwell tach, and I get the same thing: No high or low RPM's. I get a volt reading and an amp reading, but the dwell pins the meter one way, and I get zero for RPM's.

I wired the dizzy side of the coil to the green on the gauge. I also tapped the dizzy side and the other side of the coil with the dwell/tach, but no luck!

I have an ACCEL after market "Super Stock" coil that is rated at 42,000v. Could this coil be what's at fault? There is no problem running or anything, I just can't get RPM readings to set idle, and the mixture. I know you can "dial in" on this "by ear", but I want to set up to spec.

THX...K

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Old 10-26-2003, 11:31 PM
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Hmmm...... all that green wire does is count spark events for the electronics in the meter which convert it to an analog voltage that displaces the needle. It just sees the 12v primary exciting voltage so it doesn't matter how hot the secondary voltage is. The meter is lit by the red (+12v) and must have a a good black ground. Standard electrical question is 'Are you sure you have a good ground?' Does the light in the meter light up? Does the case need to be grounded and you are on a plastic dash (really digging there!)? If ground is good and you are sure the terminals are on correctly and conducting electricity, take the tach back to the dealer. These are very simple meters and if oyu are doing everything correctly, it must be bad.
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Old 10-27-2003, 12:17 AM
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Yes. When it didn't work inside, I went outside directly to the bat, both sides, and the green to the dizzy. At first I thought it was the gauge. But I did the same thing with my dwell tach, and it didn't register RPM's either. The dwell/tach was a hand-me-down that I haven't used before, but it did read voltage and amperes. But the dwell itself pinned in the opposite direction of where it should have been.

So both the Sun Tach and the dwell/tach are not registering RPM's. Yes the Sun tach's light glows when hooked to the bat and when wired inside. Is it possible they are both bad?

I can always give them a test on the 'Bird. Where would the green go on the HEI?
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Old 10-27-2003, 12:37 AM
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On the 'tach' terminal on the cap...

If it's a standard HEI with the coil in cap, the Tach terminal is next to the Bat terminal, and just outboard of the 3-pin plug. Your green wire goes there...

Doc
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Old 10-27-2003, 08:40 AM
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Murphy says both can be bad!
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