Headlight Mod... what about trailer lights

[Mikes91]

Does the headlight relay mod only take the load off the switch when headlights are used (i.e., doesn't affect the switch as far as trailer lights go?)

How would I go about taking care of the 15-20 or so lights on my horse trailer, too? Wiring up the parking lights? Is a 20A relay sufficient? There are lotsa lights on that trailer, plus 2 or 3 large interior lights for the horse section and tack room.

Is a fuse needed on the trailer portion of the circuit? The relay can handle xx number of Amps... what about the fuse in the fuse box? I suspect I'd blow the relay before blowing the fuse in the trucks' fusebox if I try to pull too many amps?

Also, can anyone post specific part numbers for the mod? Relays, fuse blocks, etc.?


Thank you,

Mike

 

[yARIC008]

Well yes, if you only do the headlight mod then it only takes load off the headlight part of the switch. For some reason on my van there it already comes with a relay to power the running lights. You basically just need to do the same thing you do for the headlights. Rig in a relay to take the load and have your headlight switch do the switching of the relay.

 

[MIDNIGHT RIDER]

I suggest you go here www.cummins-conversion.com and read through the trailer section there. I found a wealth of good info there and have employed a lot of it to my own equipment.

 

[Mikes91]

I suggest you go here www.cummins-conversion.com and read through the trailer section there. I found a wealth of good info there and have employed a lot of it to my own equipment.

I read those posts awhile back... didn't see anything specifically that answers my question.

Mike

 

[soulpatchfr]

um, Mike...

clicky

you might want to check out the many recent threads re: headlight switch mods & anything close. just look at all the thread titles for the last month - seems to me that there have been quite a few lately that answered (or linked to) everything relevant.
might even go back a page or two.

are you running the trailer harness through the running light circuit? did you tap into the brakelight + wires yourself? i've read that there's a harness tucked away back there just for the trailer (does it already have a relay???) - haven't looked for it yet, myself. being a City Boy, i don't pull much...

 

[reklund]

there IS a separate wiring harness for the trailer lights, with a separate fuse in the under-hood fuse block.

 

[Dalvaras]

there IS a separate wiring harness for the trailer lights, with a separate fuse in the under-hood fuse block.

there is no under hood fuse box or seperate trailer harness on my 1991 F250

 

[Magoo]

Some years and some models have the trailer harness and some dont. If it does, the relay and or the relay wireing can be found just behind the coolant resivour (sp) on the driver side. The loom to the back is tucked up in the frame rail next to the tank. It is in the black plastic loom and the tips of the wires have shrink tubing on them. I believe you will find them on "all" F350 and "most" F250. The super plain janers did not get the wiring. My expierence has been that Ford put the relay braket and the wire harnes is pretty much everything but left out the relay and the actual 7 prong trailer plug unless it was specificly orderd. Here is an example that is similar. The company I did some work for bought 100 new (03 and 04) F350 4x 6pacs. Every truck came with the trailer loom and relay mount (no relay instaled) and they had the day time running light relay and wiring installed (again no relay installed) but the company specd the trucks with out those options thinking they would save money. As a side note. I researched this because the Fleet manager wanted automatic daytime running lights and trailer plugs installed. Turned out the running lite issue was a $16.00 add on per truck (just the relay installed) but to buy from Ford (dealer only relay) was $75.00. Same with the trailer plug. $25.00 per truck (relay and plug installed) after market ended up 30 and change. So moral to this story is 1. Ford installed most everything allready in the factory on most if not all the trucks and 2. Sometimes its cheaper to get the goodies when you spec your truck. (this for those who may be buying a new truck in the future).
The wire for the trailer if I remember( I can look at mine today) has the yellow, green, brown, black, white, red and Blue wires.

 

[Mikes91]

clicky

you might want to check out the many recent threads re: headlight switch mods & anything close. just look at all the thread titles for the last month - seems to me that there have been quite a few lately that answered (or linked to) everything relevant.
might even go back a page or two.

are you running the trailer harness through the running light circuit? did you tap into the brakelight + wires yourself? i've read that there's a harness tucked away back there just for the trailer (does it already have a relay???) - haven't looked for it yet, myself. being a City Boy, i don't pull much...

Thank you for posting the link... I remembered a message containing it... just couldn't find it last night for whatever reason.

If I recall, the trailer lights are run through a harness under the truck. I don't recall that it has a relay, but will get under there tonight and see what we have. The RV place that installed the trailer hookup was reputable and I suspect they did the job the RIGHT way... but you never know anymore... It just seems to me that the switch shouldn't be burning so quickly if only the stock lights are being used. I just had all this stuff replaced in July of '04. Pulled the horse trailer once since then. Pulled a car trailer from Georgia to California. That's it. So 2 pulls and I already burned stuff up.

Now, the U-haul car trailer plug is the 4-pin type. If I recall, there's a 4-pin plug on my truck that may very well be wired through the headlight switch.

Maybe I could buy a 6-pin connector and build an adapter to make the other end work with the 4-pin type for pulling U-hauls car trailers...

 

[reklund]

For what it's worth, my truck had the factory installed wiring, as people said. I did have a relay and fuse under the hood and a factory Ford 7pin trailer plug. The 7 pin plug on my truck (with a Ford logo on the cover) is a large semi-truck style 7 pin plug. It is NOT the common 7 pin RV style plug with flat conectors. Mine uses round pins. I ended up buying the proper connector for my trailer, rather than changing the truck to the new style plug, which really works great for preventing my friends from borrowing the trailer or truck (wrong connector)

Ryan

 

[MIDNIGHT RIDER]

The trailer lights should be on a completely different circuit with their own switch, completely isolated from the headlight switch.

This is extremely simple to accomplish by running a fused 10 gauge wire from a hot battery terminal to a big toggle switch, then to the TM terminal on the truck side of the trailer plug. It doesn't get much simpler or safer than this.

The Ford lighting system is notorious for being a truck burner.

 

[Agnem]

Unless your truck came from the factory with the trailer towing package, then you don't have the relay and wiring.

 

[Mikes91]

The trailer lights should be on a completely different circuit with their own switch, completely isolated from the headlight switch.

This is extremely simple to accomplish by running a fused 10 gauge wire from a hot battery terminal to a big toggle switch, then to the TM terminal on the truck side of the trailer plug. It doesn't get much simpler or safer than this.

The Ford lighting system is notorious for being a truck burner.

What does "TM" mean? I assume knowing that would tell me lots re: how to identify its function.


Thank you,
Mike

 

[MIDNIGHT RIDER]

In truck lingo, TM means Trailer Marker, which means trailer lights.

 

[Mikes91]

In truck lingo, TM means Trailer Marker, which means trailer lights.

Thank you.