AE92 tacho not working with MT LT10s

**BoostBoy** · 17-03-2007, 01:25 PM

I've got a Microtech LT10s with x4 Ignitor box and 4 Bosh coil packs wired up to my AE92 turbo 4age, but now the factory tacho doesn't work. I've tried a few suggestions from other sites and all I could dig up was replacing some resistors and diodes on my factory tacho board, but that didn't work.

One other suggestion I'm yet to try is to add a 1W Rectifier Diode on each negative wire of each coil and a 15V Zener Diode on the wire to the tacho. Also a 1K Resistor to ground.

I've seen this wiring diagram on a few forums, but can anyone confirm for sure this will work for me before I rip my dash out again and butcher some wires?

**LeeRoy** · 18-03-2007, 02:17 PM

Would the tacho not work for 2 reasons maybe?

- Incorrect signal shape either square or wave
- Only getting 1 pulse not 4 like standard.

- LeeRoy

**sideshow** · 18-03-2007, 07:13 PM

you need to use one of my tacho boosters which i use on most microtechs

pm me and i can send one COD if you want one

**Hen** · 19-03-2007, 11:14 AM

Assuming the AE92 dash tacho was originally fed from a coil negative signal (basically true unless it ran a 4AGZE from factory) you can use either of the following:

- A signal booster from the Microtech tacho output. As seen here. And Viper Nipplex has posted a guide to building one of them.

- 4 diodes, a resistor and a zener on the 4 signals to your coils. As seen here.

Some more info.

Hen

**DX20VT** · 19-03-2007, 06:54 PM

Originally Posted by Hen

Assuming the AE92 dash tacho was originally fed from a coil negative signal (basically true unless it ran a 4AGZE from factory) Hen

Nope.

Almost all toyota 4age's feed the tacho from the EXT terminal on the igniter,
which is not a coil -ve feed.
( although a factory tacho will work from coil -ve )