TACH

[fiat218]

how does a tach work off of, , i mean it said the wires goes to the coil? hows does that make a tach work

[Tappy]

if i educated myself well this would be a a simplistic way to tell how it works


An electric tach reads the pulses from the coil or distributer. Kind of like an old school timing light. You hooked up to the coil and spark plug wire. Pull the trigger and every time the plug wire is charged the timing light flashes. Count the flashes and thats the rpm. Same principal

and then you might ask how the coil works :

The ignition coil is the component that connects directly to the vehicle's battery and includes two transformer windings. The primary winding feeds into the distributor, while the secondary winding connects to the spark plugs. The distributor's cam rotates in unison with the engine's compression cycle. When enough energy has been created, the spinning cam opens a breaker, which causes a high-voltage jump in the ignition coil. This voltage surge is transported to the spark plugs, resulting in the necessary electric spark to begin ignition.

[fiat218]

well thank u tappy. any chance chance is a tach, actually to point where it does not work? gauge itself

[danaspider]

If the car is working, I would lean toward the tach itself or the wire to the tach. Running car means the coil is firing.

[fiat218]

well thanks, i was gonna check the tach and well one thing led to another, now i see the altenator need work, lol. so i get that done tomorrow then back to the coil

[azygoustoyou]

Wow Tappy,
I wish I lived near you. Then maybe I would learn something.

[mbouse]

is a '69 tach the same as a '74 tach? if so, i may have a '74 tach, should you find you need a different one.

[fiat218]

how would u know if the tach is bad

[mbouse]

does the car run?
does the tach function?

yes & yes means you have no troubles

yes & no, means suspect the tach or the wiring between the tach and coil

no & no, could be any number of issues.

the tach is an electrical meter with mechanical operation. they can fail. check all connections to insure they are sound electrically.

[fiat218]

yes car runs, tach don;t lol
im looking into the wires, i hooked it up and still no go

[mbouse]

well, you are playing with a forty year old wiring system. #1 thing to go wrong is that the grounds get corroded and will fail.

start by cleaning your grounds (all connections) then clean the other connections & tighten all the connections.

then,providing everything is connected according to the wiring diagram..and unless there has been an electrical fire... i would suspect the tach is not functioning.

please obtain a wiring diagram, and trace those wires.
http://artigue.com/fiat/pubs/Wiring_1969_1973.pdf

[fiat218]

i got the wire leading to the coil, it there a way to test that wire for no breaks, i mean it brown and it goes to the tach, could i see if there current going thru it ,.

[fiat218]

i seen that my altenator wire was green and broke, so ima get a new one, what amp? would be best, im not sure what i have just yet

[mdrburchette]

You can't go wrong by going with a bigger gage wire that was originally used.

[fiat218]

i am gonna try run a wire across to see if it works then i will know