I am trying to figure this out on my 24v set up as well. One thing you should know if you dont already is that you will need a set of vacuum valves that Y into the vacuum system and send the pulses for minimum and overboost turbo. I got a set from G&S, but I assume theirs are all 24v. They then sent me this info on wiring which I have not yet followed up on:
None of my EWDs cover the 12H-T boost switch/LED set up. But looking at the
back of the tach you have a plug with 3 wires, one yellow, one Green-blue
and one Yellow-red. One lead (yellow is my guess) is going to need
instrument cluster power. The striped wires are probably the ones that need
to go to the pressure switches which ground to the body when the pressure
reaches certain PSI.
I would make yourself some small jumpers and use a 12v battery to figure out
what does what on the LEDs in the tach.
Hopefully 12v is enough to light em up.. if not you may need to get 24v to
test em.
What I can't figure out is if/how the LEDs will light up when you turn the
key through acc, run, start and everything lights up on the instrument
cluster (test pattern)
I went through this on my 1HD-T 80 swap but I had the EWD for the 91 HDJ81
and it was pretty straight forward. Power got to the LEDs inside the tach
IIRC
May the force be with you. If I come up with an epiphany I will let you
know.
-------
Please let me know if you get yours going.
