Bought the HD analog tach/speedo combo. Installed it 2 years ago...has worked perfect until about 2 months ago...started randomly blowing the instruments fuse. Might happen once a week or just every now and then. weird this is, the lights, fuel gauge, gear selector, warning lights etc all still work. The tach itself and the speedo do not. I assume since it kept randomly blowing a fuse, maybe their is a short somewhere, but its not under neath the dash gauge,i have gone over it with a fine toothed comb, all looks good. Which wire should i check on the gauge (only has 1 plug) that controls the tach/speedo functions. If makes any difference, I have andrews 57H cams, power commander 5 with autotune, and rush racing exhaust.

 

here is the speedo in question....


I have also tried to put the factory speedo back on, and it doesnt work either

 

I have the same one on my '09 FatBob. Took the ECM out to reflash and when I reinstalled it, the odometer died.

 

You say that when you put the Factory Speedo back on it doesn't work either but you do not say if it blows a fuse.

It sounds like the problem might be elsewhere than the Speedo/Tach . . . if you still randomly blow fuses with the original installed then you know that it is in other wiring.


Spurious or random shorts are hard to find. Start with a good thorough inspection especially at any corners bends or connections.

Having a fuse in and wiggling wires around may also expose it by popping the fuse.

 

it never blew the fuse with the factory tach, and it has a good fuse in it now.
I have taken all the fuses out, replaced with new and cleaned the fuse contacts with contact electrical cleaner and brushed them.

 

May sound silly but check your battery connections especially the ground, both the wire and the ground post. Also check your battery...seen some weird electrical issues when the cables were loose....