Installing a tach, what did i goof up?

[MightyTex]

Hey guys, thanks for looking! I'm installing a sunpro aftermarket tach. I thought it was straightforward enough with 4 wires, but when I got it all hooked up it doesn't work. :bang:

So first off, it said to hook the green wire to the (-) terminal on the ignition coil. Is this correct?

20012

[geezer101]

Black is obviously the ground/earth lead, white is the back light illumination and the red needs a connection that is only live when the ignition is on. Just swap it to the +ve side of the coil and see if it works. I am getting conflicting info on where to hook it up (seen both +ve and -ve!!?!) but your truck did come with a factory tacho option which means there is a trigger wire in the instrument socket in the back of your dash cluster. It may even have the 'trace' indicated on the back of the instrument cluster which would mean all you need to do is bridge your tacho into it and you're set.

[MightyTex]

Swapping it to the (+) terminal seems to have done the trick! I wonder who wrote their instructions... :shrug:
Thanks for the help!

[geezer101]

Swapping it to the (+) terminal seems to have done the trick! I wonder who wrote their instructions... :shrug:
Thanks for the help!

This is a result from what I call "Englitch" - plans printed in English, sent to China for production, then translated to Mandarin, then the installation instructions are translated back to English. I have seen about 4 different wiring instructions for the Sunpro tacho, I bet most of the tachos end up dying from the bad wiring instructions... but you got it working so it's all good :thumbup:

[pennyman1]

on the 2nd gen trucks there is a wire in the harness on the firewall in the engine compartment.

[GotToGo]

on the 2nd gen trucks there is a wire in the harness on the firewall in the engine compartment.

Could you be a little more specific?

[royster]

Could you be a little more specific?

I took a photo for you. These connectors were installed so that options could be installed quickly. If you ordered your truck (when it was new) with the sport cluster, this is what they hooked the tach up to.

20093

My SunPro tach is wired directly to the coil.

For newcomers who don't know - that metal plate on the firewall has your engine type on it (i.e. 4G64) so you don't need to put "other" in your engine info (below "vehicle"). When we can glance at your avatar area we can see what engine you have, and can make better suggestions specific to your needs.

[GotToGo]

Cool, thank you!

[GotToGo]

Yeah, I don't have one of those.

Is there still a tach wire somewhere?

[geezer101]

Yeah, I don't have one of those.

Is there still a tach wire somewhere?

Yeah the '88 won't have it as it's pre FI. Those extra connections are for the ECU diagnostic and tune reset. You won't have to worry about a bad sensor or ECU :P The trace for it should still be in the main instrument socket plugged into the dash. Isolate it and life is easy. I know you're going to ask me what colour is it - I've McGoogled it and can only find schematic diagrams. Typical...

[royster]

Yeah the '88 won't have it as it's pre FI

Yikes ! My bad - but I'll know in the future to pay closer attention to the year of the truck.

[GotToGo]

Thanks, I'll see if I can find it.