i've got an '80 f-150 4x4. i recently installed a different instrument panel from a '80 bronco. the replacement has a factory tach. other than the tach, the panel is the same as the original one. however, the tach doesn't work. all the gauges work fine. what can i do to fix the tach?

thanks for the help

 

Make sure all the connections to the tach are connected and clean.

Inside the engine compartment on the Left fender skirt there are a couple sets of connectors next to the duraspark module.

There should be a set of two connectors with a Dark Green/Yellow stripe wire going into them. One comes off the coil tach test poll, to the one connector, it splits the wire to two wires, one goes to the duraspark, the other goes to another connector, very close to the first, that plugs into the main cab harness. Make sure these connections are tight and plugged in.

If everything seems ok there, and the tach still doesn't work. It's time to check for continuity in the tach wires.

Remove the coil connector from the coil, and unplug the two connectors described earlier.

Check for continuity between the coil connector, tahc test wire, and the first connector on the other side of the ignition harness, using a ohmeter or a continuity test light that you can buy cheaply at any parts store.

If no continuity fix wires between coil and the connector.

If you got continuity, check between the two connectors that connect tach wire from the ignition harness and the main harness. this splits the tach wire to the tach or to the duraspark. The wire between the connectors is very short say 3 inches.

If you got continuity, go on to the next step, if not fix the wires.

Now check continuity between the second connector on the main harness, and the instrument cluster connector, inside the cab.

If you got continuity go on to the next step, if not fix wiring.

If you found that the Dark Green/yellow wire has continuity all the way from the coil to the instrument cluster connector, then check to see if you have power at the tach. In the instrument cluster connector find the Black/light green stripe wire, and see if you have power to this wire with the igniton switch is in the on position.

If no power is present check the ignition switch for proper operation.

If power is present at the Black/lt green wire, check the ground to the instrument cluster connector, black wire.

If you have a good ground, check the printed circut for any damage, or missing copper. Make sure the connector and the connection in the cluster are clean and tight.

If still no luck, then you have a defective tach and replace it with a new one.

Hope this helps you out.