Tic Toc Tac Reading High

• Tuesday at 6:46 PM

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69 SBbyBB

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I just installed a FBO ignition control box with the Pertronix coil. The engine runs great, but the Tic Toc Tac reads 1800 rpm at 875-900 engine speed. The error seems to be proportional. The higher the engine speed, 4000, the tac is over 6000.
Has anyone had this?

 

• Tuesday at 7:04 PM

• #2

pnora

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If it was OK before I would call FBO. You can buy a replacement board and calibrate the tachometer. RTE sells it.

 

• Wednesday at 5:35 PM

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The tach was restored by The Tach Man in 2013 and worked great. FBO said I need a diode in the tach wire off the coil. She didn't say what the size would be. A diode doesn't make sense to me.

 

• Wednesday at 6:38 PM

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hunt2elk

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You do need a diode. One didn't come with your box?

 

• Wednesday at 7:19 PM

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RJRENTON

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hunt2elk said:

You do need a diode. One didn't come with your box?

Click to expand...

Please be specific......and which direction is it connected??......with current flow (- to +) or opposing current flow (+ to -)?? Just curious as to the diode's function????.....
BOB RENTON

 

• Thursday at 6:33 AM

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I only got the control box and the Pertronix coil. The gray tach feed wire is on the coil - , like the FSM shows. An answer to Bobs question will help.

 

• Thursday at 7:25 AM

• #7

hunt2elk

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This is the diode that comes with the kits. A call to Dana, who bought out Don, should get you one in the mail. I was actually the one who got Don and Shannon at Redline together for this diode solution as apparently I was the first one to have an issue with the tach not reading correctly.

 

Last edited: Friday at 12:14 PM

• Thursday at 7:29 AM

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hunt2elk

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69 SBbyBB said:

I only got the control box and the Pertronix coil. The gray tach feed wire is on the coil - , like the FSM shows. An answer to Bobs question will help.

Click to expand...

Bob's question?

 

• Friday at 7:44 AM

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RJRENTON said:

Please be specific......and which direction is it connected??......with current flow (- to +) or opposing current flow (+ to -)?? Just curious as to the diode's function????.....
BOB RENTON

Click to expand...

Your answer with the diode info did it fine. I'll call Dana again and get the diode from her.
Thanks everyone!