Speed, would be really helpful to know what type of vehicle you are installing into, and also what type of head unit you're installing. But honestly if it's working ok per the instructions you received from your friend - I'm not sure what the problem is.
Nothing wrong with pairing the switched and full time 12v wires together. The reasons most head units have both a switched and full time;
1. Switched wire - so your radio doesn't stay on when the ignition is turned off
2. Full time - to save radio presets and time
Sorry, i should have stated that at the beginning.
I'm installing it in a 85 Nissan 720 ST. The radio... i have no clue, its the stock radio out of a 91 toyota tacoma. The harness im splicing to looks like this:
On mine 5 and 11 are hooked together and a single wire leaves from 5. And my yellow is apparently antenna power (number 20)... So that leaves me with 1 red wire and a ground out of the radio and 2 wires and a ground out of the dash.
I also don't have 13 and 19 as shown on that diagram.
And i would agree there is no problem, i just wanted to increase my knowledge, that is i would but i do actually have problem now.
So i had it working as stated but in order to do so i had bypassed a blown fuse, on the yellow wire, and once i got it working last night i picked up a new fuse to put one in. But when i put it in after work this morning the radio quit working, and it refuses to work even if i bypass it again. I don't think i screwed the radio as it worked right up until i cut the truck off to put the fuse in, so i hope i didn't screw something on the truck. I did check, all my fuses both inline and on the panel are good. And everything else on the dash works, including the cig lighter on the same relay.