Resolved: Tachometer Light Stopped Working

[The Mindless Philosopher]

HELP (if you can)...

I have what was at the time a brand-new AutoMeter Pro-Comp Silver tachometer (not the shift light version). It replaced a much older one of the same model. It has seen maybe 1,000 miles since installation. Now, all of a sudden, the lighting does not work. The tach needle is still doing its thing like it's supposed to, so no worries on actual operation. I've traced the wires, and all four (red, green, black, and white) are in place and their terminals are snug. Any ideas why the lighting would suddenly stop working? Is this a common glitch with these things? I can't find the information I need in internet searches. Has this happened to anyone else, and were you able to solve the mystery? I'm running a MSD HEI distributor, if that helps? Do I just need to live with the lights not working? Do they burn out that quick? If not, it's a bit pricey to replace the whole unit yet again.

[BossHossMan]

Here is the link for your wiring diagram: https://www.autometer.com/media/5795_56 ... 9_6811.pdf
It looks like the white wire needs 12vdc to light your gauge. If there is no 12vdc when your key is on, take a look at your fuse and wiring back towards your battery.

[The Mindless Philosopher]

Here is the link for your wiring diagram: https://www.autometer.com/media/5795_56 ... 9_6811.pdf
It looks like the white wire needs 12vdc to light your gauge. If there is no 12vdc when your key is on, take a look at your fuse and wiring back towards your battery.

Thank you for the link, BossHossMan. All I could find were diagrams with a shift light. My tach doesn't have one. That link is exactly what I needed.

I traced the wires, and sure enough, the shop had tied the red wire in with the white (12V dashlighting) when they had installed the tach. Following the diagram, I disconnected the red wire from the white and routed it to the ignition switch(+) terminal. The white wire is where it needs to be, and the entire run appears to be fine.

Unfortunately, nothing changed. The gauge light is still not cooperating. At least the tach needle still works. I'm not gonna throw away more money on another tach just to have something I can see at night, though it irritates me to no end that it's practically brand new, and it decided to give me the middle finger. But then this trike has been giving me the finger for four years. I need to find my voltmeter and maybe buy a set of probes. This blind monkey work is for the birds.

Thank you again for the link.

[The Mindless Philosopher]

...And...the king of over-thinking strikes again! The tach's light bulb is as black as pitch. It is TOAST!

Maybe I didn't over-think the situation after all, because...

the burnout was most likely from the red and white leads having been tied together? Hard to say, as they both run on 12 volts so who knows?

At least I've corrected that, but now I need a bulb, too:

AutoMeter 3218 or GE86.

[The Mindless Philosopher]

The tachometer is not working. I need to put the wiring back like it was.

[BossHossMan]

I have been away for a couple of weeks so I just saw that you are still having some issues. Yes put the wiring back like it was. It is okay that the two 12vdc wires were tied together. Take a volt meter and turn the handle to dc voltage. Put the black lead in the "common" hole. Put the red lead in the hole that says VDC. Put the black lead to ground on the trike. Put the white lead to the red and white wires. You should get a reading of 12-14 volts when the key is turned on. Do you?

[The Mindless Philosopher]

The issue is resolved. It was a dry rotted crack in the insulation that was arcing (or grounding? - whichever) on the frame. This whole trike needs to be rewired. It has not aged well for whatever reasons.

[knockdolian]

The issue is resolved. It was a dry rotted crack in the insulation that was arcing (or grounding? - whichever) on the frame. This whole trike needs to be rewired. It has not aged well for whatever reasons.

The wiring on a Boss Hoss is not complicated. Mine is earlier than yours. All the wires are black which doesn’t help. This is a very good diagram I got with mine. Once I can lift my Trike body I will re wire it. The diagram is for a bike not a trike. But you get the basics

[The Mindless Philosopher]

The issue is resolved. It was a dry rotted crack in the insulation that was arcing (or grounding? - whichever) on the frame. This whole trike needs to be rewired. It has not aged well for whatever reasons.

The wiring on a Boss Hoss is not complicated. Mine is earlier than yours. All the wires are black which doesn’t help. This is a very good diagram I got with mine. Once I can lift my Trike body I will re wire it. The diagram is for a bike not a trike. But you get the basics

Thank you for the diagram!

One mild irritation with my Hoss (2001) is that I don't have that wire junction under the tank between the front end and the fuse block. Instead, most everything is honed back to a giant round plug that runs the length of the main tank.

I will likely build a junction eventually to make troubleshooting and repairs easier.

Most of the wires are black, and most are labeled from the factory. My eyes are getting a little wonky with age, so it's mighty tough to read the stamps on the insulation anymore, but at least I do have that. The rear of the trike is a bit more of a challenge.