The truck is an '83 with an Auto.
It is also the 'High Sierra' version.

With the lights on I have no tail lights. When I turn on a turn signal (either direction) both tail lights blink.

When I picked up the truck, none of the lights worked at all. Awhile ago I went to the junkyard and grabbed a male and female connector that mounts right onto the rear of the bumper and wired it back in. There was a hacked job of wiring done to wire in trailer lights. Well, it's wired back to the way it should be per the haynes manual, and it's the same damn thing.

Could a bad relay or something of the sorts cause this issue?

 

why the hell were you up at 4:10 am dood? Did you get my caps son?

 

i bet there is a bad ground somewhere, or like you mentioned a bad relay. did u check all the fuses?

 

I checked and rechecked the grounds and fuses for him. The only thing it could be is a relay, or something touching somewhere in the column or on the firewall.

 

are there more than 1 relays that are the same? you could try swapping some to see if they make a difference. other than that, check for something grounded out like you said, near the firewall or even near the taillights or anywhere there is a clusterfuck of wires

 

Im not sure for relays, it was 11pm when I did it. I checked from the firewall back to the lights for grounds. I searched every wire by hand and felt it the whole way. It has to be from the bottom of the firewall into the cab somewhere... it cant be any further than that.