Electrical 4cyl to 5.0 tachometer wiring

[VasiliBrown]

I recently got an 85 coupe that was swapped from 4cyl to 5.0. Im trying to get the tach to work. The red wire with green stripe is going to the positive on the coil and the green with white dots is going to the negative. Still doesn’t work. How do I wire the tach up?

 

[90sickfox]

If it's a factory 4 cylinder tach you may have to remove the tack and select for v8. The 4 cylinder tach won't read right for a v8 unless it has the selector on the back. Some cars had them and some didn't. There was a write up on it here a while ago. An aftermarket tach will need chassis ground ( black ), wire to negative side of coil ( green ), and a 12v ignition switched positive wire ( red ). The white wire is optional and is 12v for the back light.

 

[VasiliBrown]

If it's a factory 4 cylinder tach you may have to remove the tack and select for v8. The 4 cylinder tach won't read right for a v8 unless it has the selector on the back. Some cars had them and some didn't. There was a write up on it here a while ago. An aftermarket tach will need chassis ground ( black ), wire to negative side of coil ( green ), and a 12v ignition switched positive wire ( red ). The white wire is optional and is 12v for the back light.

so it does have the selector switch but it's not reading at all, that's what lead me to believe it was a wiring issue. do you know where the factory wires go?

 

[90sickfox]

I don't off hand. I did find that the common cause is fuse 18 it's a 15 amp blue fuse. Controls other things too. It says the hazards are on that same circuit.