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Reusing Stock 620 Tachometer Connector


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I'm trying to repurpose the original 6 tachometer wires for using a speedhut tach in my 79 king cab. I Is there anyone here that can confirm my beliefs about the wires?


Based on the screengrab below of the '79 wiring diagram, you can see the original 6 pin tach connector & how I traced the wires out:

L (blue): Signal from distributor    LW (blue/white): switched power    RB (red/black): power from light switch    B (black): ground    RL (red/blue): power from light switch    BG (black/green): power?



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Pretty much correct. The Blue/White is only used for the clock option and is a continuous supply not turned off by the ignition. I added 620 to the title so that the search function would differentiate from all other tach wiring and save people time if searching for something else.

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Okay, that makes sense. Based on that diagram, the distributor signal goes to nothing & that blue/white wire powers both of them, which I figured was incorrect. It makes sense that the clock needs constant power while the tach wouldn't. Thanks, Mike!

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Yup the L or Blue wire is shown wrong on the tach side with L and LW to the same terminal. The diagram you posted is for a '78-'89 and shows the clock at 10:10 the '76 and '77 diagram shows the plugs upside down and facing away from each other to yours and the clock reads 3:00.

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