another crazy tach - Third Generation F-Body Message Boards

wwwyzzerdd · 06-22-2009, 05:53 PM

i hate to keep coming on here with problems and not giving anything in return, but ive searched and searched trying to find a solution to my tachometer problem, so dont say i havent tried the search, ive looked through quite a few threads

, im thinking its something at the coil or a bad ground, because ive bought 2 tachs, both from v8 cars from upullit, and they both do the same thing as my original, so i doubt its a resistor or a bad capacitor, it either stays pegged at zero when running or slowly rises until it pegs at 7000 rpms, this is at idle or driving, doesnt matter, and when i turn on my right blinker the tach starts bouncing all over, i also tested with my voltmeter, running on ac settings from the coil wire in the dash to ground, and i get jumpy readings

does anyone have a complete wiring diagram for the tach?

thanks

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wwwyzzerdd · 06-23-2009, 03:07 PM

hate to bump, but this is the last thing besides the oil pressure gauge that i need fixed, and it would be nice to have all my interior working like it should

Chevy8588 · 06-23-2009, 09:48 PM

sounds like either a short in the wiring for the cluster, or the flexible plastic circuit board on the back of the cluster. here are the wiring diagrams for the tach and the cluster circuit board.

wwwyzzerdd · 06-23-2009, 10:39 PM

awesome thanks a lot, ill start looking at it tomorrow

92RS(real slow) · 06-24-2009, 01:31 AM

have you recently changed to a different coil?

wwwyzzerdd · 06-24-2009, 07:13 PM

the tach has been messed up since i bought the car, i have no idea what has been done to the engine before i bought it, all i know is it was converted to carb by the previous owner

wwwyzzerdd · 06-26-2009, 08:07 PM

i ran a wire directly from the coil to the tach itself, i didnt run a wire to the gauge cluster, i ran it around the cluster to the coil lead on the tach, and i got different results, but all 3 of my tachs still do the same thing, except this time they stay at about 5000 rpm, none of them peg out, i know i still have a short somewhere in the cluster or somewhere because my blinkers are kind of screwy, but what does this say about my coil? can that even go bad and the engine still run?

L98FORM89 · 06-27-2009, 08:32 PM

stock or aftermarket ignition? Had a similar problem with my MSD ignition, it needed an additional module.

wwwyzzerdd · 06-27-2009, 08:35 PM

stock im pretty sure, how would i check? i dont know what mightve been done to it in its past

WhtIroc · 07-03-2009, 02:19 AM

Mine's the same, stuck on 7000 and doesn't move. Everyone who gets in the car is like, OMG we're going seventy?? and I'm like nooo... just 65. The speedometer is over here.

acsport2 · 11-03-2009, 07:28 PM

Mine is stuck at 7000 and dosen't move either.88 iroc tpi swapped to carb and hei.
Very interested to hear the solution.

wwwyzzerdd · 11-04-2009, 01:35 PM

i still havent fixed this, still cannot figure out whats wrong, but its still doing the same thing as described

z28 TPI · 11-04-2009, 03:02 PM

Hmm curious pegs at 7000 rpm. Is the distributor HEI or does the distributor have the coil on the side? Easy way to check is there a wire in the middle of the cap or is there no wire in the middle just a big bulge. Reason being that there might be a difference in the reference signal for the tach in the 2 different dists. I will look at the wiring diagrams and see if I can help you. Have you checked both harnesses leading to the gauge cluster for rips tears in the conduit, broken wiring in the conduit, or fried wires? I will look at the diagrams I have and see if there is a solution to your problem.

wwwyzzerdd · 11-05-2009, 12:53 PM

the distributor just has a bulge on top, no wire, wires come out of the side of it, i had another distributor that came out of another camaro, although i dont know the year or anything of the other car, the distributor was for an 8 cyl, and it looked the same as mine, and it had a pin on the side that said "tach" or "coil" something like that, so i looked at that wiring diagram above, and wired a wire from where it said tach or whatever on the distributor, and then directly to pin 11 on the gauge cluster, and the tach just pegged at either 0 or 7000..

thats as far as i got, and i gave up on that for the time being

NINÅ · 11-05-2009, 03:04 PM

The turn signal interacting with the tach sounds like an open ground.

Take care of that first so it won’t throw you off when troubleshooting.

After you fix the turn signal problem and the tach still pegs your problem is probably the circuit board mentioned in post 3.

It sounds like the IC is defective.

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z28 TPI · Yesterday, 01:01 PM

Nina you are right on the open ground. Wwwyzzerdd i would really look at the wiring harness in the back of the cluster. when you turn the signals on somewhere in the harness those light are grounding out on the tach signal wire thats why it moves. After that I would check the continuity of the tach signal wire coming off the dist. it should be white in color and run to the drivers side firewall. I fthe wire color switches it would be at the connection in the firewall, but in my experience GM doesn't do that. Anyways follow that wire to the gauge cluster which means when you get to follow the wire inside the car i woulds start taking the conduit apart and follow to wire. Hope this give you a start to fixing your tach.