I am adding some back up lights to my truck....I found out the other day that it really sucks trying to backup a trailer up while dark and raining!!
I don't want to have them come on with the backup lights all the time, only with a switch that I will install for them.
This was how I was thinking of wiring them up.....12v from battery...inline fuse.....on/off switch with indication light.....to lights at hitch.....and ground where necessary...
OR with a relay so I cant accidentally leave them on...
85-ground
30-fused 12v from battery
87-aux lights
86-12v from ignition to switch to 86
Sound about right?
Which one is the best way to go?
Also what size fuse do I need (lights are 55w each, total of two lights)...I picked up a 30a fuse, also got 14g wire...
you don't need to run the power all the way to the battery, you can tie into the trailer plug power and use the relay.
I have "white knight" back up lights, work great. The housing fits around the hitch and has a switch on the backside for on, off, or on with backup lights only.
The relay setup you described is what you want. You can find a 30 amp automotive SPST relay pretty easily. As for the current, each light is rated at 55W, that means you will be dissipating 110W of power, at 12V that is around 10 amps pulled through a single conductor. I am assuming that the 55W rating is for a 12V system (you should verify that). 14 gauge wire should be plenty for that. However I would go with a smaller fuse than 30, because 30 amps is about the limit I would put for 14 gauge. I would go for a 20 amp fuse myself; those are plenty common and easy to find.
The relay setup you described is what you want. You can find a 30 amp automotive SPST relay pretty easily. As for the current, each light is rated at 55W, that means you will be dissipating 110W of power, at 12V that is around 10 amps pulled through a single conductor. I am assuming that the 55W rating is for a 12V system (you should verify that). 14 gauge wire should be plenty for that. However I would go with a smaller fuse than 30, because 30 amps is about the limit I would put for 14 gauge. I would go for a 20 amp fuse myself; those are plenty common and easy to find.
Thanks for that info...I will go with the relay....I will also pick up a 20a fuse and take the 30a back...I was thinking that it was on the high side myself (edit:wait a minute... I think the lights come with a fuse already...Will have to wait and see when they get here!)......as for the relay I have a bunch of ford relays out of my old fuse box...these would work right?
Regarding the old Ford relays, it's hard to say. Do they have ratings stamped on them? It is important when you build something to make sure that all components being used are safely within their limitations. Contact current is especially important with relays because of the danger of contacts welding shut. I know that a lot of those old Ford relays were used on things like the horn, which take less current, so I would make sure that whatever you are using is rated for the current you will be working with, with an added safety margin.
Regarding the old Ford relays, it's hard to say. Do they have ratings stamped on them? It is important when you build something to make sure that all components being used are safely within their limitations. Contact current is especially important with relays because of the danger of contacts welding shut. I know that a lot of those old Ford relays were used on things like the horn, which take less current, so I would make sure that whatever you are using is rated for the current you will be working with, with an added safety margin.
It is actually out of my 06....I just added the new towing mirrors with heat and did not have heat before so I needed a new fuse block.....Now I have all kinds of relays and fuses out of the old one....let me see what the manuals says they are for....
R01 is starter solenoid, fuse is 101 at 30A
R02 is blower motor, fuse is 116 at 30A
R05 is trailer tow charge, fuse is 106 at 30A (I'm using this relay in the new fuse block)
the rest look to be fuse at 10a .....(accessory delay and hi-beam head lamps)
So I should be good to use any of the top two?...although the part numbers on all of them are the same....
It is good design practice to size a fuse such that any circuit element downstream of the fuse can short to ground, and the fuse will blow before any element in the path cooks. In a perfect world, this would be the case, but I do not know personally whether or not Ford has done this in every case. I don't like making assumptions..."should be" isn't always "is." Therefore, it's hard to infer a device's amperage rating from the fuse size. Maybe someone more familiar with those part numbers can chime in and tell you if those specific relays are okay to use, but if it were me I'd just use a new relay with specific ratings from the manufacturer. They are abundant and can be had for a few dollars. That way there's no guessing. That's my 2 cents!
It is good design practice to size a fuse such that any circuit element downstream of the fuse can short to ground, and the fuse will blow before any element in the path cooks. In a perfect world, this would be the case, but I do not know personally whether or not Ford has done this in every case. I don't like making assumptions..."should be" isn't always "is." Therefore, it's hard to infer a device's amperage rating from the fuse size. Maybe someone more familiar with those part numbers can chime in and tell you if those specific relays are okay to use, but if it were me I'd just use a new relay with specific ratings from the manufacturer. They are abundant and can be had for a few dollars. That way there's no guessing. That's my 2 cents!
I sent an pm to one of our sponsors (FTE/parts-guy) and he confirmed that the relays are 40A....more then enough......I also got the lights to day from Fed-ex and they include the inline fuse, which is a 15A. I will be using what they gave me so I can take back the stuff I bought from oreillys.
I will post up pictures when I get them installed in about a week or so.
Join Our Site - Its free, quick and easy!
