Tach installed, works like crap.

pistonhead351 · Sep 4, 2007

I got a stewart warner 5" tach with shift light for free. Its was brand new and in the Box. I got it installed, all the wiring is correct. Both the ground for the illumination and the tach are run to the battery, red to a 12v key on power source and green to the - on the coil. The tach works but as soon as it gets over 2000 rpms it jumps all over the place? i was leaning towards the coil being bad, but the stock tach works great. Do you guys see anything i did wrong here. Or is there something im missing?

ryan218 · Sep 4, 2007

something you either did or the tach is bad... make sure all your wires are tight. ..hence why you got it for free maybe

pistonhead351 · Sep 4, 2007

actually my uncle bought it new and he gave it to me because im supposed to work on his trailer. i am dead sure that everything is right. i was leaning towards the tach being bunk myself to.

woodyy24 · Sep 4, 2007

does it have a switch for 4-6-8 cylinders?

Strype · Sep 4, 2007

Try putting the grounds on the fender well... Mine was touchy with the grounds

pistonhead351 · Sep 4, 2007

no it does not have a switch for cylinders that im aware of. I believe stewart warner is diff than autometer. it reads close its not doubled or anything. where at in the fender well strype?

Bad92GT · Sep 4, 2007

i run my green wire to the positive side.. works like a charm

blackened88lx · Sep 4, 2007

woodyy24 said:
does it have a switch for 4-6-8 cylinders?

I would look into this further. Could be under a cover on the back or something.

90five0oh · Sep 4, 2007

i got a 5in with shift light for christmas but its an auto gage which is made by auto meter and it does the same thing but not all the time....its really weird

pistonhead351 · Sep 4, 2007

the stewart warner tachs dont have loops like the autometers, they have Ppr or Pbr haha cant remember, its calibrated for a v8.

woodyy24 · Sep 4, 2007

blackened88lx said:
I would look into this further. Could be under a cover on the back or something.

yep. even my 2'' sunpro tach in my cavalierrlaugh had a switch under the cover.

Darkwriter77 · Sep 4, 2007

FWIW (and IIRC), the tach in my notch (big honkin' Autogage with external shift light) had WIRES in the back that determined 4-6-8 cylinder modes. You snipped one or two of the wires depending on if you wanted it to read for 6-cyl or 4-banger modes, or left 'em all intact if you wanted 8 cylinders. Had to remove the rear cover to see this, though.

Others will mostly use the ol' switch method. Just make sure it hasn't been set to something other than 8 from the factory (or prior owner).

Also, double-check your grounds. What sort of connections did you use? I usually cheap out on most of my electronic accessories and use crimp connectors (such as with stereo stuff), but on a tach, I would VERY highly recommend using ONLY soldered connections.

If all of the above checks out, and your coil is good ... whelp, the tach is probably junk.

pistonhead351 · Sep 4, 2007

this tach works diff than autometers. all of my connections are soldered. im giving the tech line another call tomm.

MAC'n89Blckstng · Sep 5, 2007

my signal wire hooked up to negative side of the coil

Strype · Sep 5, 2007

pistonhead351 said:
where at in the fender well strype?

Mine is connected to the inner wheel well with sheet metal screw. Had to drill a hole first, it's kinda tough. My first attempt was using the radio ground and it wouldn't work.

Darkwriter77 · Sep 5, 2007

I grounded mine to the dash support frame thingymadoohickey under the radio. Just take a bit of sandpaper and rub it down to bare metal before you go screwing/bolting down your ground.

HISSIN50 · Sep 6, 2007

You don't have an ignition box do ya?

pistonhead351 · Sep 6, 2007

nope but i think im gettin one.

ike34 · Sep 29, 2007

Did u ever figure out why it was doing that, im having the same problem?

cevtv · Sep 29, 2007

Bad ground.

Tach installed, works like crap.

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