If it has the tow package, there will be 2 relays alongside the under hood power distribution box. One is for the 12v charge wire for the trailer battery and the other is for backup lamps I think. All of the 7 wires needed for the trailer plug will be run to the back of the truck. It will likely have a 7-pin round plug on it if anyone has used it to tow with. Also, the relay and fues locations inside the power dist box that are for trailer lights will be filled with the relays and fuses.
Thanks for the information. I don't think it came equipped with the tow package. the only thing it has at the rear end of the truck is the flat 4 pole plug for trailer lights and it is spliced into the rear lights with a T one. I think I am going to have to buy the wiring kit along with a control box to work the brakes on my trailer.
I have looked at this site several times and found it very useful. Today I decided to go ahead and join.
Maybe I'm stupid. I went out and checked under the hood also just for grins. I found the power distribution box under the hood. I opened it and it appears that there are fuses and relays for the trailer brakes. The truck wasn't used for towing before I bought it so the absence of the 7 or even 6 pin plug does not really help me.
Maybe I should look a little harder under the rear end to see if there are 2 more wires somewhere for the brakes to hook into.
I'll keep looking and let you know where I end up.
I believe that the tow pkg included the 7-pin connector (and wiring). If your truck doesn't have that, it probably doesn't have the tow pkg. I bought my '97 HD used so I'm not 100% sure about options, but it has the OEM 7-pin harness along with a plug under the dash to connect a brake controller. Other things my truck has for towing include an engine oil cooler & aux tranny cooler.
I bought the brake controller and the wiring adaptor today(my truck does have the plug in under the dash). I also crawled back under my truck just to take a look and I found where the flat 4 pole plug ties in to the brake lights. I also found another round plug that was just plugged in to a plastic retainer. There are 3 wires coming from that. After finding that and also finding that there are fuses and relays in the power distribution box for trailer lights and brakes, I am beginning to think the truck did come with the factory installed towing package.
Trucks with and without the tow package have the brake controller plug-in under the dash, so that's not a deciding factor.
My truck didn't have the tow package and when I investigated the relay/fuse locations in the under-hood power dist box, I found that there were only wires connected to those plug locations on the incomming side, not the outgoing side. Also, the blue brake controller wire comming from the plug under the dash dead-ended at the firewall junction. There were no relays on the side of the power dist box either and there were no extra plugs on the wiring harness going to the rear of the truck. I got trailer lights from a T-One connector that fits in the factory harness connection for the right side tail light harness. Brake control wire had to be run seperately. I didn't bother with the charge wire.
My truck did have the factory aux trans cooler in front of the radiator though, so that's not necessarily an indicator of tow package either. It did not have an aux engine oil cooler, but I don't think any 351 engines got that, even with the tow package, or at least I haven't seen any so far.
I installed the brake controller and round 6 pin connector on Friday. I used two of the heavier wires from the round plug I mentioned in a previous post that was just plugged in to a plastic receiver. I connected the 4 pin to 6 pin adaptor to the flat 4 pin connector that was already installed. This left 3 wires that were not connected to anything (green, red and white). The white is obviously the ground wire. The round plug at the rear of the truck that was not being used was cut off and had 1 green wire, 1 orange wire (probably faded red) and one black smaller wire. I connected the green wire from the adaptor to the green wire on the truck and the red wire from the adaptor to the orange wire on the truck. I left the black wire on the truck loose (not connected to anything). I attached the ground wire to the truck frame.
On the way home from getting the tractor it didn't seem as though the brakes were working on the trailer. Once it dries out a little I am going to have to check the wires I connected to at the back of the truck for power.
Should one have constant power and the other have power only when the brake pedal is depressed?
If this is the case it should be easy to troubleshoot why the brakes where not working. I also pulled the trailer while it was empty and it was pretty clear that the brakes were not working.
I don't know where I go from here. Does anyone have any suggestions?
I am not going to be pulling the tractor much at all but since the trailer I bought has brakes, and since I went to the cost of buying the brake controller, I would like to see the brakes work.
The brake control wire is hot only when the brake pedal is pressed, or when the controller is operated seperately by hand. The constant hot wire should be the trailer battery charge wire. The other wire should be the backup light wire.