I have a 1988 GM v6 4.3 liter on my boat. I know this is not a boating forum but I think this same engine was used on a Blazer and was a very common engine of the period. I am trying to troubleshoot a non-working tachometer. Where should I look first? One of the tach leads goes to the spark coil I think which is common. Help much appreciated. A primer on tachometer wiring would also be appreciated.

What is the make/model of the tach?

I have no idea. The tach is old and installed in a panel. I'm sure it is conventional for the time period. Could you please give me some idea of where to check the wiring? I'd guess it'* a bad connection or fuse but where should I look? I assume you're familiar with this engine. Thank you.

Is it part of the instrument cluster or an add on?

It'* an add on. Remember this is a boat. I just would like a typical wiring scheme for a tach. Thanks.

What time period are we discussing?

​​​​​​​​​​​​​​Typically:
White = Internal light
Red = 12V+
Black = Good engine ground
Green = Tach terminal on coil

This is extremely helpful. I knew it shouldn't be too complicated. This tach has no gauge illumination if that'* what you mean by "internal light." Then the spark frequency relates to the engine rpms and "drives" the gauge, is that correct? But which terminal on the coil attaches to the tach? Many thanks for your help to this point.

It gets connected to the negative side of the coil.

Thanks again. The last time I looked that connection looked pretty corroded. Will check everything over and report back next week. Hope your weekend is great!
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