aftermarket tach

[kjchristopher]

I didn't turn up much in a search for hooking up an aftermarket tach, other than the blue/yellow wire, which agrees with the wiring diagram I've got (Apex). However, I'm not getting a signal to the tach or data logger. I'm getting a pulsed voltage if I hook up my DVM, but nothing on a gauge. Is there a trick to getting a tach signal to a data logger (DL1)?

Thanks!