Another tach question

[Leiger]

My dad hooked up my tach awhile ago and it worked great for about 2 days, then i let it sit and the TACH drained my battery. So i have a short in it. Has anyone had this problem before? And no, the backlight doesnt stay on when the key is off. Im sure ill figure it out soon enough, but if anyone knows whats goin on, please let me know. Thanks everyone!

 

[dyeager535]

Short?

I'd suspect that the 12V power wire is not connected to a switched battery source. Tach needle will likely NOT stay at 0 RPM when there is no voltage to it. When you hit it with 12V it should snap to 0.

What year is your truck? Plenty of accessory terminals (some switched) on the '80+ fuse panels.

 

[Leiger]

I have an 88 V10 Blazer......he apparrently hooked it up to a non switched sorce like you were saying. Im pretty sure I can hook it up later tonight but i young and dont know quite a lot about it all.....im pretty sure i could find a switched source pretty easily but im not sure if there would be any side effects of me tapping into the fuse box for power. Where would be the best place to hook the tach to?

 

[dyeager535]

Along the top row are a bunch of single blade connectors. Some may be filled already, but you can piggyback on some of them.

Take a test light or something and make sure that you get power only with the key in run. Some will be hot all the time, and there are some other variations as well. You can use a spade connector on the wire and just stuff it in there, but GM used those connectors on cars the same vintage, so if you want something that locks in place, the wrecking yard is a good source.

You'd want an inline fuse, those accessory terminals on the fuse block are all ganged up on 30 amp circuit breakers.