914 Tachometer not working Options

[vin man]

I've done some searching and have not yet found a thread that I'm sure has been covered at some point.

The tach in my 72 does not work. The car was converted from fuel injection to carbs long ago. I believe the reason the tach does not work is because it is no longer getting a signal from the computer (no longer have an ECU in the car).

How does one use the factory tach when I no longer have FI? In other car projects, I just ran a line from negative side of the coil to the back of the tach. But I don't think that will work here, will it?

[timothy_nd28]

There is already a black with purple stripe wire that runs from the tach to the negative terminal of the ignition coil. All 914 tachometers read the tach signal from the ignition coil, not the computer.

So back to your troubleshooting, there is only 3 wires needed to make this tachometer work. The two outside terminals on the tach should have a brown wire while the other wire should be red with white stripe. These are the power wires. You should measure 12vdc between these two wires with the ignition switch is set to on. The middle wire (black with purple stripe) is the signal wire. You will want to ohm this wire from the negative terminal of the ignition coil to the middle terminal of your tachometer. You should get 0 ohms.

If all that fails, you may have a bad tachometer.