wiring to fuse box

[sdyer233]

For my tach install i need to wire to a constant power source, how would one wire into the fuse box correctly? would this be the best option?

 

[coloradodave]

Strange that a tach would require a 'constant power' source. Normally just a keyed 12 volt source, a ground and a signal. What brand of tach is it? Model #?

 

[sdyer233]

thats more of what i meant, excuse me i know next to nothing about electrical. should i tap into a 12v source then?

 

[coloradodave]

Yes, one that is only 'hot' when the key is in the on position. If you go to an auto parts store and pick-up a fuse tap (a small connector that will insert next to the fuse in the fuse box and has a flat 'male spade connector' exposed, a few female 'spade connectors and a test light, you'll be able to do it right. Ground the alligator clip of the test light to a bolt under the dash and then touch the pointed end of the tester to one side of a fuse with the key off. If the tester light doesn't come on, turn the key to 'on' and repeat. You want to find a fuse that has power only when the key is 'on'. A good fuse to look at is for the radio. When you find the right fuse insert the bent end of the new connector next to one end of the fuse. Then connect your tach power lead to the connector utilizing the female spade connector and appropriate sized wire. Good luck with your project.

 

[bigmanjbmopar]

Not sure about anything below 68 but on mine there are taps built into the fuse box, just look behind it you will see male lugs on the 12vdc source and switched sides of the fuses holders good ole' Chrysler was thinking when they designed it.

 

[sdyer233]

thanks guys, i contacted charger specialties and they clarified the issue, had to alter the wiring harness that i got from them

 

[HT413]

Just be careful with the dimmer circuit for the instrument panels. That will obviously cause some issues for anything but the tach light. For my 69 belvedere it's the far left circuit when looking at the back of the fusebox (the connection side, not the fuse side). It's an orange wire. Obviously the way to test to be certain would be to check voltage with the lights on and confirm voltage when the panel lights are dimmed.