[dpoltzer]

The factory tach in my 70 formula was working perfectly and the next day it started acting erratically. The needle goes to "0" when key is off and it stays right at 1,000k when engine is running but needle hardly moves when idle is increased. Sometimes the needle drifts towards 1,500 but no higher. I did replace the coil the day before the tach started acting up. The wire from the tach to the coil is new and I checked the fuse and it is fine. The connection at the coil is clean and tight. After reading here I thought there might be a ground issue so I ran a jumper from the tach housing to ground but no change. Also ran a jumper from the cluster mounting screw to ground and still no change. Any ideas on my next move? Thanks again.

[Lloyd-TX]

Weird, but I believe that you may have already answered your own question - there's something screwy with that new coil?

[superdutybob]

You have the wire on the negative side of the coil?

[dpoltzer]

Yes the tach wire is on the "-" side of the coil. Maybe I should swap the coil out (Under warranty) and see if that makes a difference? Thanks guys.

[superdutybob]

Originally Posted by dpoltzer

Yes the tach wire is on the "-" side of the coil. Maybe I should swap the coil out (Under warranty) and see if that makes a difference? Thanks guys.

I only asked because I made that mistake one time. It was the first thing that came to mind.

[SD73]

I guess I'd try swapping out the coil too, if I had it under warranty. But, I don't understand how a bad coil would affect your tach reading AND let your engine operate normally. Still, if you can swap it I'd give it a shot. After that I'd check continuity on that new tach wire just to make sure it's good. If that fails then the only thing left is the tach being suspect.

[dpoltzer]

Well I swapped out the coil and the tach still does not work properly. Unless there are any other suggestions I guess I will remove it and have it serviced? I was think about using "The Tach Man" in Greer, SC. Anyone here used his services or any other recommendation in the Atlanta area?

[Formulabruce]

The tach ( cluster) needs a good ground, I would check tach with cluster sitting on the lowered steering column with a test ground wire to chassis first

[dpoltzer]

Tried that with a ground wire from the case to ground and still no work!

[dpoltzer]

Called Gary The Tach Man and he said he cant get parts to repair my tach. If I have to buy one of the reproduction Tachs, does any one know if will work correctly in a 1970 Formula?

[GREGGDOG]

For my 70' Formula, I used Speed-o-check to restore my tach, and all other gauges. Great work, Mike helped me out.

Speed-o-check
12353 Whittier Blvd # C, Whittier, CA 90602
Phone: (562) 464-0699

[Bentwheelbob]

Try Pete Serio. He's active here on PY, a Pontiac guy, and does great work.

pserio@columbus.rr.com

[dpoltzer]

I have spoken to Pete (Very Nice Man) and he said he would see what he could do. I guess the "movement" is difficult to repair and hard to find if it must be replaced. I noticed in the parts catalogs that the replacement Tachs are for 1973 thru 1975. Anyone know if they would work in a 1970? Thanks.

[Bentwheelbob]

It would work, but not sure if the color gradations, and the RPM at which they occur, would be correct for a 1970. Compare the tach face colors of the repop to yours and see. It may not be a big issue depending upon how correct you want it to be and how OCD you are. Best bet before you throw away good money is to send the tach to someone who can bench test it and determine if the tach is good or defective, and if defective if it is a curable problem. That's the only way to be sure if the problem is the tach or something else.

[FrankieT/A]

I believe the 73 up tach is a 2wire and 70-72 is a 1wire but still doable.

[SMW]

I had problems with the tach in my 73 Firebird. When I pulled the tach out of the dash and looked at it I saw the small circuit board came loose from its mounts. I pushed it back on and it worked.

[dpoltzer]

I will remove the cluster next weekend and inspect for an obvious problem. Thanks

[rexs73gto]

If when you pull it out & all the part look good, look real close at the circuit board as over a long period of time like your 70 model tach, the board can crack & give you all kinds of problems. If you see it has a crack in it send it to Pete I think he is able to fix most of them with a new board if thats the problem. I haven't used his services yet but have heard lots of good things about his work on most all tach concerns..

[dpoltzer]

I will be in Columbus in a few weeks and will take the cluster to him for inspection and repair. I have two or three other tachs from 73-77 cars in case he needs to borrow parts from one of them. Concerning the circuit board, I don't think that has much if any effect on the tach as there is just one wire going from the tach terminal to the distributor for signal to operate. Thanks for the input.

[SD73]

Have you tried swapping in another tack as a test?