Is THIS the infamous yellow-and-black wire to hook up a tach? '97 GTI

[bajaman123]

I got my tach in the mail the other day, looking for some final advice on hooking it up. I found a yellow and black wire in the engine bay and in the nose. Is this the one to splice into to power the tach signal? See pictures.
Additionally, this tach has two connectors, with two purple, two black and one gray. I assume the purple is + and the black is -, and I need to hook BOTH of them to power and ground? And the gray wire to the yellow and black wire, with a 20K ohm resistor in line?

Thanks for the help.

 

[soccerdad]

I cant answer your question. But I would find a schematic for your ski and the donor ski and look at them closely. Manuals and schematics are available online for most of these. It should be pretty easy to figure out once you have both schematics.

 

[Sportster-2001-951C-Stock]

Power and signal are two different things, you'll need ground as well. A trailer type test light will help confirm power on with key on, or voltmeter, and marine tach signal has always been a GRAY wire since my birth, sometimes it's not.

Forgot to mention, Purple is normally power with key on. Red or yellow are often constant power.

Not sure about your boat specifically, these are marine industry standard colors.

 

[Strizzo]

You'll need to add a pin to the mpem harness in the correct location and wire it to the grey wire on your tach for a tach signal. Power will come from the other gauges power when you daisy chain them together. That's why there are two power plugs. The ones that used the red/black wire from the stator were much earlier models. Wasn't that you that posted about this before?

 

[bajaman123]

I've commented on the posts on this subject before. Now that I am actually doing it, I am simply looking for information from those that know. For example, why are there two power and two ground? Will one set or the other work, or do both need to be connected to power and ground? As far as the tach signal wire goes, the information on the Forum in previous posts indicates to find the 'yellow and black' wire from the magneto and install a 20K ohm resistor in line to condition the 'signal'. I was asking if anyone knew for sure if the wire in the picture was from the magneto. Since that post, I've looked at the wiring diagram in the factory service manual I have, and confirmed what I need to know...as far as the magneto wire is concerned. I'll be doing some testing on the tach later with my multi-meter but I'm pretty sure either set of the power and ground wires will work, I suspect the dual harness was simply how the 'ski this tach came from was set up, likely it powered another gauge.

Thanks again for the replies.

 

[Sportster-2001-951C-Stock]

Agree, the electrical schematic should tell you most everything needed, if you have one. One thing to watch for with power and ground, is power should drop out with MPEM power down. Otherwise, the tach will continue consuming power and run the battery down even though it's not receiving a signal from the ignition. I'm sure this is obvious to you already.

I don't have the specific schematic, so probably can't contribute much more. I guess the power would come from the power that's daisy-chained from gauge to gauge, usually purple.

 

[Minnetonka4me]

Yes...20k ohm pigtail off that yellow black wire, or install the "grey" wire on the MPEM. Not even sure if there ever was one on the GTI mpem for any model...have to check a bunch of schematics.

 

[bajaman123]

I got the tach installed and the power and ground wires hooked up, ran out of time before I could hook up the tach signal wire. Maybe next weekend.