Help figuring out a short circuit on my 66

[70BurntRt]

I bought my first 66 charger a couple of months. I have other second and third generation chargers but I am not familiar with this car yet nor do I have a manual. Everything was working fine until last night when I lost all dash lights, interior lights. tail lights and brake lights. Also, I don't know if this is related but before that happen the tach went erratic and then stayed full tilt all the way to the right. Any thoughts or advice would be helpful.
Thanks

 

[black64]

Start with checking your grounds. Seems that losing all at once is ground related. Start with body to engine ground. Also bulk head connetors.

 

[brad 66]

be carful under there . there is 300 volts coming from the power pack . I done loaded a manual .

 

[Fran Blacker]

Service Manual at this website. http://www.mymopar.com/index.php?pid=109

 

[A383Wing]

you have crusty rusty corroded fuses and fuse connections at the fuse box under the drivers side of the dash

 

[70BurntRt]

I tighten up the coil wire and got my tach back. I checked the fuses and changed one them. The connections don't look that bad. Cleaned up the connections to the rear light harness and still no changed. There is a small relay that looks crusty behind the driver kick panel. Its screwed to the side frame and it sits behind the frame. A red wire from the main dash harness is plug in it. Anybody know what that is? I ran out of time and will have to check the grounds later this week. Thanks for help.

 

[A383Wing]

that is not a relay, it's a circuit breaker, use a test light to see if you have power to both terminals