The big round one...that I've never used... on my 01 PS 7.3

It doesn't work, the small flat 4 does, as do 2 flat 4 ones that I"ve wired in.

I now have a trailer that needs that big connection, where do I start looking? I've done all the fuses. Seems that its gotta be something fairly simple that I'm overlooking somewhere.

Thanks, Jeff

 

did you test it with a test light? do you have a brake controller?

 

You didn't overlook the under hood fuses did you?

 

I believe there are 2 square relays that need to be installed under the hood to make the big plug work. The relays usually come with the brake controller pigtail from the factory.

 

Checked ALL fuses, but did not know about the relays.... only checked what was installed, did not read further.

Have no brake controller yet, but do seem to have a pigtail and there may be relays in that bag, will definitely look. I was thinking it almost had to be something like that.

No juice with a voltmeter or test light...

Thanks, Jeff

 

Check fuses 3,4 and 8 under the hood. In mine the relays were there, just not fuse #8. The relay are under one of the two little black covers beside the main fuse block.

 

think lights are supose to work without the extra fuses and relays
where I found my problem,the seven prong plug plugs into the harness at the bracket right at the plug and that plug was corroded
it done this in a matter of weeks

 

And fuse #1 under hood for Left Stop/Turn Lamp, on my 99 anyway.

 

That wasnt to long ago was it Barry, you were adding revearse lights wasnt it?

 

Nope, just helping a friend straiten his mess out. I still have the fuse diagram and his was a 01. Your right about #1, I missed it. Here's the layout for trailer fuses and relays under the hood.
#1 Trailer Tow Left Stop/Turn Lamp
#3 Trailer Tow Right Stop/Turn Lamp
#4 Trailer Tow Back Up Lamps/Trailer Tow Park Lamps
#8 Trailer Tow Electronic Brake Illumination, Park Lamp, Trailer Tow Park Lamp Relay Coil.
All of the above are mini fuses.

#38 and #39 are relays, 38 is a trailer tow backup lamp relay, and 39 is a trailer tow battery charge relay.
Yours may be like my buddies and some one disconnected the 7 round plug from the harness to wire a 4 flat in line with rear lights. It works for 4 wire, but to use all 7 wires, in could brakes, battery charge, and backup lights, you need the fuses and relays under the hood.

 

Just noticed I left out two maxi fuses under the hood.
#16 is the trailer tow battery charge
#28 trailer tow electronic brake controller
Both are 30amp maxi fuses