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In my 71, which still has the OE tach, which was converted to a circuit board but looks OE because the distributor was replaced with an MSD w/o the cable drive for the tach by the ( PO ). It still works, but it’s acting up and I don’t trust it. I called the company that rebuilt it and they said that the circuit board is on its way out. Which explaining why whey you shut it off, the tach buries on redline and the needle is erratic when running. Thats why I wanted to replace it. I purchased a new tach,( Bosch, looks like the old 60’s Sun tach ). I hooked up the wires per the instructions. On initial hook up I had all the wires except the wire going to the neg side of the coil just to check the light. All was good. After hooking up the neg coil side wire and I started it, the tach did not work. Nothing, not even the tach light. I then found a blown fuse, the one marked
DIR SIG - BACK UP. It’s a 20A. The bottom fuse port is not marked. But pics I’ve found show it being marked as gauges. I believe the yellow wire going to the neg side of the coil is for the tach, ( that’s what the company that rebuilt the end said ) Wiring diagram for Sun tach. Not my fuse panel, but looks like it.
Do I need to disconnect it before the Sun tach will work? I’m lost with wiring… Never was good at it. Thanks for helping. Steve.
Bosch/Sun tach install Not working
