77 Trans AM Tach Won't Go to Zero
 

Hi Guys, my tach works fine. When I shut off the car it does not go to zero. So, I am not sure its accurate when the car is running. Thoughts on a fix.. thx

If you tap it ( with a little force) will it return to zero?

No, won't return

disconnect the tach lead to/at the distributor and see what happens.( with key off!). we'll go from there.....how far away from zero is it?

Those old analog meters have 2 very tiny flat wound copper springs in them. As the meter ages ( from use or from lack of use, car sitting, does not matter) those springs weaken. Those are soldered in-place and that is not something that you could repair. Those 2nd Gen trans am tachometers have a "forced" zero position which is not like any previous GM car tachometer design. They can do that when the springs are brand new, the springs are what give the meter it's zero position at that counterclockwise angle.

All 1970 up to I think 1977 or 1978 trans am tachometers which were built with the old analog style meter do that.

At this point the only cure for that is to replace the tachometer.

thx!

I am working with a company right now. They are one of the last companies left in the US that is still in operation who can make old school analog meters.

Presently they are working on new meters for me, they fit the in-dash 1965-67 GTO rally gauges. I restore these gauge sets and I need new meters for the tachometers.

If we can work out a few things on the sample and get those made, next in line I have plans for them to make new meters for me that fit the '68-72 GTO & Lemans factory in dash tachometers. If all that goes well I am going to have them take a look at the 2nd Gen trans am tachometer meter.

These meters are all permanent magnet and moving coil meters which are the meters that GM put in these gauges when they made the cars years ago. Unlike all the current imported reproduction tachometers the original meter's pointer gently floats back down to the zero mark after you turn your engine off. The GTO meters 64-72 are all assisted by the weight of the pointer (return to zero) but the 2nd Gen trans am meters; that pointer is in opposition to it's zero mark so the copper springs attached to the moving coil are the thing that gives that meter it's zero return.

Great work Peter.. apparently I am ignorant on these newer tachs.. ..I am more familiar with the earlier tachs... (72 and earlier)....Thanx for all you do!

I got the latest sample GTO meter in yesterday and put it onto a board this morning.

All I can say is we are real close, they need to make one more revision to my meter and the early GTO meter will be perfect!

Next up is the 68-72 Lemans & GTO. I am going to send them 2 sample tachometers: a 68-72 GTO and the 1970 & up trans am tach/clock combo in the gauge housing in about a week or 2.

Last fall a customer sent me 2 original trans am gauge sets; one out of a 1970 and the other out of a 1971. That job is for some pretty nice restoration car(s). These are both blue cars with a white stripe. The color you usually see on those early cars; is bright white with a blue stripe. Basically that is what got me started on this. More to follow......

Any updates? Have a 79 that needs help as the rpm is dead.

Must be Hoyt in NH

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