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Can Someone Identify The Trailer Tow Relays

13K views 3 replies 3 participants last post by  lancew13 
#1 ·
On my 2001 F-350 SD 7.3L Diesel...

I am trying to figure out all the relays and fuses that I need for trailer towing. I installed a Prodigy brake controller with a pre-made adapter harness but it wouldn't power on (worked fine in my other truck which I removed it from). I found in my owners manual that I needed a 30A at #28 position, in the under-hood block, for "Trailer Tow Electronic Brake Controller". I swapped a fuse into #28 and the brake controller powers on. Most other fuses are present that seem to have anything to do with a trailer, other than #16 "Trailer Tow Battery Charge" which I may or may not use.

I cannot locate the positions listed in the owners manual as #38 "Trailer Tow Backup Lamp Relay" and #39 "Trailer Tow Battery Charge Relay". Does anyone know where these are?

In the attached picture, the yellow arrow points to the fuse for brake controller power but what are the red and blue arrows pointing to? Are one of these possibly positions #38 and #39?

Thanks for the help.

Lance
 

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#2 ·
Yes the other 2 arrows are pointing to relay boxes. I didn't remember there being 2 separate relay boxes under the hood. If that's a pic of your motor you need to stick some relays in that box on the left. I remember on a 99 the brake control pigtail came with 2 relays and a fuse you had to install for the brakes to work.
 
#3 ·
Yep, the blue arrow is pointing to the trailer power/backup lamp relay box. Don't remember which is which, but it shouldn't take much to figure it out. I recall mine being backward from what the book said.

The red arrow points to the transfer case ESOF relays, one for motor travel in one direction and the other for the reverse direction.
 
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