Tachometer - Wiring Inquiry

[rwantin]

Hello,

Still sorting a few odds and ends on my recently acquired MK IV. Yesterday, decided to investigate the tachometer, which has never worked in my possession.

It's a 4" Speedhut - it lights up and jumps a small bit when powered on, but that's it. In looking at the connections on the coil (Pertronix distributor and Flamethrower coil) I noted two wires, in addition to the distributor wires, added on, orange and green. I THOUGHT those were the tach connections, but apparently not. Second thought was a kill switch of some sort, but not that either (the car cranks but does not start with these wires disconnected). Is this some sort of facility for EFI and the loop is merely being closed?

I also checked the Speedhut site. It appears one yellow wire to the negative side of the coil, which seems simple enough. I pulled the tach and yep, there's the yellow wire. Except it is obviously routed elsewhere. Could/would it have been installed elsewhere? Next steps, pull the dash (I've done this twice) and trace?

Thanks (in advance) for any guidance and/or insights.

[rwantin]

Forgot to mention, my car IS carbureted.

[gkp200]

I'm probably the last person who should help with your problem as wiring is my weakness. But I just fixed some of my wiring issues this weekend. I don't see a yellow wire connecting to the coil. For my MKIV, I needed to connect to the - side of the coil to send the RPM signal to the EFI (and to the tach). You also need a power source connected to the + side of the coil to get the car to run. My wiring had an orange wire for the power source and it looks like yours is the same. I would trace the green wire back to see if it connects with your tach.

[CFranks]

Another place for you to look in your troubleshooting, my tach gets its signal from an output wire from the rev limiter (which is connected to the coil) not directly from the coil.. Not sure if that’s your problem but worth a look if you have one.

[rwantin]

I'm probably the last person who should help with your problem as wiring is my weakness. But I just fixed some of my wiring issues this weekend. I don't see a yellow wire connecting to the coil. For my MKIV, I needed to connect to the - side of the coil to send the RPM signal to the EFI (and to the tach). You also need a power source connected to the + side of the coil to get the car to run. My wiring had an orange wire for the power source and it looks like yours is the same. I would trace the green wire back to see if it connects with your tach.

Thank you! Wiring (especially not performed by myself to begin with) is not exactly my specialty either. I'm all eyes and ears, and appreciate the feedback. I'd just love to have a working tach (and know what the other wires are in the first place). :)

[rwantin]

Another place for you to look in your troubleshooting, my tach gets its signal from an output wire from the rev limiter (which is connected to the coil) not directly from the coil.. Not sure if that’s your problem but worth a look if you have one.

Excellent - perhaps that is the case here. Worth checking - so if I trace those wires back I may find the limiter.