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Fire in the Hole! But wait, no tach...
Bob,
Fired up my Cobra for the first time on Saturday. What a thrill. Nice and loud with straight headers. The neighbors love me. I noticed that the tach wasn't registering. I have an MDS distributor, but no MSD box. Using the ballast resistor. Meticulously wired both under the hood and under the dash. Where do I start? I have a multimeter that picks up frequency. Should I check for pulse frequency at the coil and then at the tach? Is there something about my MSD distributor that isn't coordinating with the SW tach? Doug |
Distributor to coil should have what you are looking for. Then you need to make sure you have power and ground ( a good ground ) to the tach unit.
If you have a scope, place a prob to that connection and see if you get a waveform. Hope this will get you started. BTW, you might want to use shielded cable for your tach lead to the cockpit. :D :D :D |
My tach, straight MSD dist, no box, was acting eratic. It was a loose ground wire from the dist, a black wire.
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Thanks guys. I'll start poking around.
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Quote:
Check your ground on the tach first. I had a problem with my ERA Tach not working when the dash lights were on due to a marginal ground. Worked OK with the dash lights off. I ran a ground from the metal dash brace directly to the tach and the problems cleared right up. Hope this helps. - Fred |
Good place to start. Thx. DD
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SW tach problem...solved
Pulled my tach out to check my connections. There are five connections on the back (and bracket) of the SW tach:
POS NEG SIG Light Ground is a tab on the bracket side SIG goes to the (-) coil POS goes to a fused power source Light, well, that's the light connection Ground is a shared ground wire from the fuel gauge NEG ---> This needs to be connected to ground.:o I had left NEG floating, having assumed the case and bracket provide adequate ground. They probably do, but NEG cannot be left floating. Tie it to ground. Tach works fine.:MECOOL: |
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