After many years sitting in driveway, the car is now running again. The dash is analog type. Everything seems to work, except tach is way off. When idling about 1k rpm, it shows 1.8K to 2k rpm. What could cause that? Is there a trim pot somewhere that can be adjusted or some other recalibration method? Thanks.

Welcome to the forum! I sent a message to our resident t-type pro. Hopefully he'll be in here soon to help you out.

Is the variance fixed or does it vary?

Fixed would be just 1k rpm high all the time, no matter the engine speed
Variable <I think linear would be a good term> would be 1k rpm shows as 2k rpm. 2k rpm shows as 4k rpm, etc.

All the stock tachs are off. There is a company that restores/recalibrates them to stock but it will never be accurate! The company is Caspers Electronics (they are on the web) also if you go the route I do when restoring GN'* add a aftermarket tach, if you do I will show you how to wire it easily. The factory knew there were issues with the stock style and added a wire and plug in the factory harness for you to add an aftermarket one!

I got your message bud! Thanks

Thanks reply. Think you are talking about the green plastic spade connector directly behind alternator. I think this is tied in some way to the ignition module 14 pin connector, but just guessing.

Have changed my module to an aftermarket BWD brand. Have heard that some aftermarket modules do not support the green clip. I did hook my dwell/tach to the green clip, but it did not register anything, so think that I might have one of those that don't support the green clip.

Don't want to send out to a shop, would like to fix myself if possible to do so. The variance seems to be almost double. I don't expect the little bar indicator to be "accurate" but would think that it should do better than that. It used to.

If have to give up the idea of fixing the bar graph display, is there another connection point other than the green connector?

Thanks.

Head over to turbobuick.com and do a search. I don't think this is something you can do yourself but maybe. The green connector has always worked for me.