Inside lights and 4 wd controls quit working
 

I acquired a 2004 blazer with low miles and 4.3 vortec.
I want to use to it to tow my 16 ft bass boat so I needed trailer light connection.
found wire and used test light to confirm each wire.
there is a large wire in this cluster of wires awiring worked as a ground.
trailers lights worked after splicing in connection but a problem has occured. Inside dome lights will not work now and the 4wd controls aren't lit up and won't work either. Went thru every fuse inside box and under hood box. Nothing blown. Swapped interchangeable relays in fuse box under hood. No results.
everything else seems to be working. I disconnected all the trailer wires and disconnected battery over night.
Anyone have a clue ??

There are quite a few fuses involved in these functions/wiring. You went through every fuse in the truck in both boxes/panels and so we know that they are all good, I don't need to supply a list to check?

George

Please do

Tell me about the trailer wiring adventure:

1. Is there anything in particular that started the malfunctions or did you do all the wires in one sitting?
2. Did you discover any wiring errors?
3. Is all that wiring completely reversed now?

After your answers Ill go over the power distribution and get some targeted instructions.

George

There was on big wad of wires jammed up in the spare. I figured it was for the trailer lights.
I got a test light and tested the tailights, turn signals and when each one tested i joined the wires together and taped them off. While i was using the test light i connected the ground clamp to the bottom of the 2 inch ball that is just in the bumper.
there was a brown wire, green wire, yellow wire and blue wire and a much larger white wire in amongst these.
I tested with the light the big wire for a ground and it did the job so I spliced the white ground from the trailer connector into it.
I had a connector that only had 4 wires on it so I didnt connect the blue wire to anything.
Brake lights worked when the headlights were off but not when they were on.
I went fishing and when I went to load the boat I noticed dome lights weren't working. Little push button lights weren't either. I also notice the yellow indicator light in the 2wd high button wasn't illuminated. The 4wd selector doesn't work now. Everything else seems to be operational. AC and turn signals, bright/dim. Wipers ....the works.

I pulled every small fuse in both boxes and none were burned apart. I swapped what relays I could to see if it was one of those but I was kind of limited on some of them.

I'll give you the fuse list tonight when I get home. Your wiring is:

White - ground
Brown - running/park
Yellow - left turn
Dk green - right turn
Lt Blue - brake


George

Alright. Thanks

Look at:

1. Park LP fuse 20A UHFB
2. Park LP 10A IPFB
3. Ctsy LP fuse 10A IPFB
4. 4WD fuse 10A IPFB
5. BTSI fuse 10A UHFB
6. TRL B/U fuse 10A UHFB
7. B/U LP fuse 25A UHFB
8. ATC fuse 20A UHFB

Did any of the trailer wiring quit Working?


George

The ctsy lamp fuse had been scuffed sometime and it looked like it was not blown but it was.
In the particular vehicle
​​​​​2004 blazer 4wd 4.3 ltr votec v6 the ctsy lamp fuse (10A) not only operates the dome and pushbutton lights front and rear it also allows the 4wd selector to illuminate and FUNCTION. If the ctsy lamp fuse is blown the 4wd cannot be switched from one mode to another.
Thank You George for the help.
David