Tach circuit board repair

[gstrandfarm9420]

 Not so recently, I had ordered a tach circuit board for my 77. when I went to put it in, the parts I ordered weren't even close to the OE unit. It said it would fit 76-81. Anyone else run into this? I really hate to spend just under 300.00 for a new tach, plus something else to make it work with HEI. Thanks

[Wallington]

For a start the 76-81 tachs are not all the same in how they work.  I guess you just found that out. Hopefully return based on their false information.

[aussieta]

the tach and the clock changed mid 1978
so you will need an early style

[gstrandfarm9420]

Thanks for replying. So what time frame are the early models included in? Too much time has passed to return this one, plus it's opened. It came from a place called West Coast Auto Parts. I will contact them. Just kept putting off tearing the dash apart, it's such a pleasure as we all know!

[Jack]

78-81 looks like half moon whereas the earlier years it's a full circle with few resistors and capacitors. plenty on eBay for $30 to $60.

[Wallington]

You can return it if they are still claiming it fits 'all years' and they are, saw the ad.

I haven't seen one listed for that version, only the 72-76 8K, and then the 79-81 6K with Quartz clock. Of course, OER do the complete tach. As Jack mentioned, you may find a cheap, ugly face tach on ebay that 'works' and swap over. I found many 'worked when removed' with that style of part, not so much when they arrived. Clocks were similar.

http://www.thepartguy.com/images/products/gauges/6K(77-79NonQtz)tach-3.JPG

http://www.thepartguy.com/images/products/gauges/6K(80-81)Tach-3.JPG

[aussieta]

wallington posted this in another post
which lists the vin cutoffs for the clock change to quartz
which is also when the tacho changed
edit link didnt appear
https://www.motortrend.com/how-to/hppp-0609-second-generation-firebird-clock-upgrade?galleryimageid=aa879a99-ccdc-4e13-a43c-e5e585fd7e91

[Wallington]

I'll also add, probably known but good for reminding, that the early Quartz clocks didn't say Quartz on the face, that was a gradual addition. But they are obvious from the rear of the gauge housing where they went from the round to the plastic case with flat sides for the Quartz clock/tacho change.