Topic: In need of guidence with mini gauge tach wiring

[elquenada]

im trying to wire up the lights on my mini gauges, tach and speedo.  Im also installing a toggle switch so i can turn them off during the day but its not working as planned. 

Im just wondering why my tach only has one wire coming from it meanwhile the speedo has two?  Will I need to solder an extra wire to the tach? How are you "supposed" to wire this tach up?

[OldSchool_IsCool]

The tach and speedo are original, correct?  The mini-gauges are some combination of volt/amp/temp/pressure and have a back light?

And you want to have the speedo, tach and mini-gauge backlights on a toggle.

Is that what you have and are shooting for?  What bike, BTW?

[elquenada]

sorry I should have been more specific.  75 cb 550.  Im not running the original tach/speedo.  Im replacing them with no frills mini-gauges (no temp or oil lights).  I just want to be able to toggle the back lights on and off.  Just not sure why the tach has only one wire for the backlight.

[Alan F.]

Which mini guages are they? Where'd ya get 'em? Got pics?
Without specific information it's tough to give a real answer, sorry.
Alan

[seaweb11]

I have 2 mini gauges on my bike, both have 2 wires. Perhaps "as said below"    the mounting plate is the ground for one of yours?

Why do you want to disconnect the back lights with a switch?

[vern401]

It sounds to me like it is grounded through the housing.

[elquenada]

ok I thought it might be grounded through the housing as well.  Im gonna try a few things and post more specific pics/questions later if needed.

thanks.

[elquenada]

I finally got around to doing this repair and I just wanted to update the thread in case others might find it useful.

My original question was basically:  Why does my new mini tach have only one wire for lights meanwhile the mini-speedo has two.

Well I eventually realized (with the help of the forum) that because the tach drive cable attaches to the engine, the housing of the tach is in fact already grounded.  Therefore, I only needed to hook up the positive lead to my power source.

Before I realized this I had wired my own ground to the tach casing.  This caused the fuse to short every time I started up the engine.