I could use a little help. I bought a Bobs F100 wiring harness to replace all the junk that has weathered the last 50 years. Everything is going well, but how do you wire in the wiper switch, brake switch and horn? I know that there are extra slots available in the fuse block, but am wondering how to access it without using inline clips. I thought that the block would have a couple of fused links that are open but it seems as if everything is being used. Anybody used one of Bobs wiring harnesses and if so, how do you access a fused power source.
Oh, by the way, I have a GM column and need to know if I need a GM horn relay or will the Ford work?
The folks at Bobs are nice and fairly helpful, but I keep hearing that the original harness did not have Hazards or a wiper switch. Thanks.

 

Julie will send you her wiring diagram. I think it in power point is that OK?

 

If I'm hearing you correctly you have purchased an original type harness but are adding modern updates like a newer column, etc. Are you adding anything else that is not in the original scope of the truck? Could you post a picture of the fuse panel so we have a better idea of what you are working with? Are you converting to 12V or staying with 6V and what year and model truck?

 

Hi Montanarodder,

I read your post and can probably help you sort this out - it doesn't sound like a big problem, but let me review it with you just to be sure I've got the message on what the problem is.

Ok it's a 56 F-100 (from your member info) and you are rewiring the original 12 volt electrical system. From what I gather, you either don't have leads for some of your accessories, or can't figure out how to cut them onto your currect power distribution/fuse panel, is that right?

If so, can you tell me specifically which accessories you are short of powering. And if you can, could you post a photo of your fuse panel? Chances are we will have to add a Fuse bar for those and that is super easy - it's just that some things like brake lights are hot all the time and somethings like wipers are switched on with the ignition - so I'll need to know.

Since you don't have enough posts to send PMs (private messages) yet, I'll check back tomorrow! In the mean time have a cold one!

Also, The horn button in either column just completes ground. And it really doesn't matter which brand of relay you use - they are pretty much the same. But, I have wiring diagrams for the Ford relay, so with Ford horns, I'd go with the Ford Relay.

 

Thanks for the information. I loaded a bunch of pics in the gallery so as to show what I am working with. If you look at the fuse block that I have, you will see three fuses daisy chained with a black primary wire. I would have thought that the extra fuse slots would have been left open?? Any way, I need to pull keyed power to the brake light sender and can use a direct wire off of the ignition switch, but should this be inline fused? Or is it covered by the 20 amp fuse in the block. I understand the horn wire now as a ground, Simple! What about wiring in a wiper switch and the hazard signals. Again thank you for your help. I know welding so I can helpo with most questions in regards to that field, but the other is self taught and I am kinda dense sometimes.

 

ME TOO !

The brake light circuit is hot (but fused and switched ) all the time for safety reasons (unless you are runnin' moonshine.)
Julie will explain.

 

Ok, my brakes work when I pull the Orange wire from the Bobs F100 wiring kit ( supposed to be for my dome light) so I know I am on the right track. Now I figured out that my horn relay was defective and have replaced it, but when I run a continuity check from the horn button to the GM black wire that is supposed to be the horn I get nothing. The only wire that shows continuity is the white wire that is supposed to go to my brake switch???? I am thoroughly confused! Any ideas? Thanks.

 

sounds like what i'm going through with someone else's wiring on my 52 f1 with an 87 5.0 efi and aftermarket a/c unit and getting rid of the service engine soon light.finding lots left disconnected or no feeds/info to the ecm.

anyway these might help to understand the gm column wiring and help to see what needs to goto what in the ford.
its a diagram for 1980's gmc/chev
oh and the horn button is only used as a ground to activate the horn relay.

i guess i have to post them in here.cant upload??

 

Oye!



Ok lets start at the begining. Did this harness come with label tags on the wires or ANY kind of instructions? This is why I hate prebundled wiring harnesses and preach the one wire at a time method - it's not you, Kevin.

Unplug everything and lets start over from the begining. Yes I'm serious.

First: there have to be two busses (distribution busses or fuse blocks). they may be contained in the same housing in your case. Your gallery says you have 105 views in there but only one picture ever shows up - the main one of the truck. So I can't see your fuse block but no matter, the wiring flow pathsa are all the same.

Ok two busses - one is hot all the time. It carries: Brake lights; headlights; horn; courtesy lights (from the door switches); glove box door light (if you have one), and lighter.

Here is a drawing of mine - imagine that each arrow is a fuse and disregard the toys - AMP number is correct fuse size for that item:



The power for this bus is provided from the battery post on the starter solenoid, up to the battery ("B") post of the ignition switch then down to the HOT bus.

The second bus is switched. Power coming off it is turned on and off when you turn the ignition switch on and off. The switched bus powers the following items: Radio; signal lights; heater; electric wipers; ignition; and guages.

Here is a picture of mine - again disregard the toys:



This bus gets power from the accessories(ACC) post on your ignition switch.

All your fuse block is, is a distribution point for 12 volt electricity -if it is wired from the power sources correctly (hot from battery term of ign sw; switched from acc side of ignition switch). From there the power goes out to the peripherals.

What you need to do is ensure the fuse block is powered correctly as I described above, then find out what fuse points (or slots - whatever the thing has) are hot all the time, and which ones come on when the key is turned on.

Then, run the wires out to the peripherals one at a time - fuse block to peripheral (item requiring power). Do the hot ones first, then the switched ones - divide and conquor - you can do this.

Take a look in my #1 and #2 galleries and there are diagrams of each switch or relay and how they are wired.

DISREGARD THE COLORS OF THE ARROWS THOSE ARE THE COLORS I REWIRED MINE TO. Just connect the dots - one box at a time. If you find you don't have enough distribution points, we'll make some more - don't worry, it's easy.

Here is a diagram of my lights scheme. The signal switch is the normal aftermarket switch we all use here - for your GM switch, it should be the same (unless God forbid the wiper switch and high beam wiring is in there too)

Already this is getting a little long. I'll send you an e-mail with my real e-mail address and get the rewire diagrams to you.

 

OK I found your pictures.

The types of fuse holders you have require every wire running to a peripheral to go both in and out from the fuse block - in other words it isn't a distribution point, just a fuse block. And it's a "bottle neck" to boot. Those will just about double you wire use.





Honestly, I would recommend you use a different type fuse holder, and you are going to need at least 12 places - 6 hot and 6 switched - there's not near enough on the one you have. And as long as you have to add more, you might as well make them both the same. I'd also go with two 9-place busses-one hot and one switched-so you can add toys later if you want to. It's ok to have some open.

I use two 10 place AGC tube fuse holders. You can get them at NAPA for about $20 ea. One wire runs down to a lug on the bottom then on the other side, the wires go out to the items - one wire in 10 wires out - not 8 and 8 like yours (I think I counted 8). I can see why you are tangled up - not a good design.

Here is a picture of mine - they are the real thing from the diagrams above. Note the copper connecting bar providing power to each fuse holder from the single lug in the lower corner. There are two lugs and bars per panel - so theoretically you can run both hot and switched from a single unit if you only need ten places - no wires for bridging - also, 2 wires coming in, 20 out - not 20 in and 20 out. If you want to switch them I will give you step by step instructions with pictures.




And the picture is a little decieving, I didn't use all orange and red wire - they really are different colors.

 

Holy cow, thanks for the help. After a couple more hours of ciphering, I found that part of my problem was that the wire that was supposed to run to the horn relay was not making continuity. I found that the horn actuator rod was not making contact under the horn button. I then found that the original relay was faulty. I scrounged another one off of a old wreck and then a trip to Napa for the new horn actuator. The horn now works. I then tackled the Hazards and still don't have then running but I think that I have this one whipped. The brake actuator works and I know how to grab power for the wiper switch after a call to Mid Fifties. Again thanks a bunch and the wiring diagrams make all the difference. I think I will stay away from the Chevy stuff!