Tach installed, works like crap.

[pistonhead351]

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]

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]

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]

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

 

[Strype]

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

 

[pistonhead351]

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]

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

 

[blackened88lx]

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]

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]

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

 

[woodyy24]

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]

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]

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

 

[MAC'n89Blckstng]

my signal wire hooked up to negative side of the coil

 

[Strype]

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]

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]

You don't have an ignition box do ya?

 

[pistonhead351]

nope but i think im gettin one.

 

[ike34]

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

 

[cevtv]

Bad ground.