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Tacho (Not Idle) Fluctuating


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#1 adam

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Posted 07 August 2016 - 08:22 PM

Gday all,

Hope you guys could give me an idea into what could be happening.

Bit if background, I have a '73 240z running an L28 with a 280zx electronic distributor, MSD 6A ignition, stock tacho with MSD tacho adaptor/booster.

My issue is the tacho fluctuates with every indicator flash, drops dramatically when the headlights are on (relays installed) or if my heater blower is on.

Note, driving/revving does not change, purely a tacho reading issue.

I have just bought a new battery and had a 280zx internally regulated alternator installed about two years ago.

Any ideas what is causing this fluctuation? It's bloody annoying!


Cheers,
Adam

#2 WA240Z

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Posted 08 August 2016 - 03:14 PM

Hi Adam,

 

One thought is the tacho is quite sensitive to fluctuating supply voltage, given you have covered a lot of bases with the (+) positive side of the supply, I would be checking the quality of your (-) ground connections. Try taking the negative supply to the tacho direct with a new wire to a nice clean ground point. Poor ground connections unfortunately dont raise there ugly head until there is load on the circuit making tracing a real pain in the neck. Hope this helps, and good luck.

 

Billy



#3 adam

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Posted 09 August 2016 - 09:51 PM

That was my next step Billy, cheers.

I am all ears for any other suggestions.




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