I'm putting some Driving Lights on my 150.
More details are at :
https://www.f150online.com/forums/sh...d.php?t=245486
I'm using two 100W GE4509 bulbs and 12 G wire.
My question is about the relay.
Any reason I can't use a simple (cheap) Ford starter relay?
Can that type relay be on (closed) for long periods?
Any reason I shouldn't connect to the High Beams (to close the relay not power the lamps) so everything (High Beams and Driving Lights) is on the same switch ?
If I do need a special Relay, what exactlly is that Relay called, ie what do I ask for?
Thanks for any help

 

For that kind of setup I would use two seperate relays, one for each light.
The two lights are 200 watts and will draw a combined 15 amps min. 13.6 volts times 15 amps = 204 watts.
I would wire a seperate fuse of 20 amp capacity right at the battery to the relays then to the lights using 10 ga stranded wire.
This way you have max protection, low voltage drop and the main lights won't be affected if a fault arises.
The cost difference is very small for the added capacity.
You could even bring one 18 ga control wire thru the firewall to a rocker switch installed in the dash fuse cover and have seperate control over the two extra lights.
All you need to do is power the relays from the headlite hi beam power and switch the ground sides on a single wire right at the dash for extra control.
I won't even ask why you want these on with hi beams! It's generally not legal on the highways.

 

Thanks Bluegrass for your reply.
Out here in Montana for night crosscountry driving I want all the lights I can get to avoid Deer. Dimming the hi beams for traffic would kill the DL's too I figgered.Adding a switch as you mentioned though would give me even more options.

Why a relay for each light? Is 15 amps too much for one relay?

 

If your state has inspection on lighting , you motor vehichle codes may spell it out.
I don't know what year your truck is but the factory usually never designs drivng lights to be on with high beams. My truck turns them off as does my 90 Lincoln Mark 7.
Driving lights usually have certain lens focus specs to prevent the light from blinding an oncoming driver on a level road and for a wider horizontal spread and fill in use.
Generally driving lights are not at 200 watt levels and project a distant beam.
I use my stock driving lights to get a better look at the sides and banks for deer standing or moveing.
I have fogs mounted under the bumper and have the selection switch to go between the two when needed but they still don't operate on high beams.
You have no idea how excited I get at some fool that mounted 'eye ball' lights or flamethrowers with no focusing lens and never bothered to adjust them.
Good luck.

 

DOT legalities aside ( IL F-150s are no longer inspected, only test is EPA, and that is DTC port and gas cap, etc )...

100 W each is 200 W total. P=VI or 200=12*I or 200/12=I. I=16.67 AMPs.

Standard 20 AMP Bosch ( or equiv ) auto relay will work fine for this application, as 80% of max load at 100% duty cycle is 16 AMPs. If you want a bit of extra margin, get a 30 AMP version ( this type goes all the way to 40 AMP ). Nothing special required for the relay.
Inline fuse holder, just get a Little Fuse MAXI fuse holder, so you don't have to worry about the wire size on the pigtails. Lot of 20 AQMP fuse holders have 14 AWG wire on them ( that is 105* C Auto Wire based calc's ).

Same for the wire, sized at 80% of max load for 100% duty cycle, 12 AWG wire will work fine. 10 AWG is 30 AMP load, which would take you to 24 AMPs, which would safely drive 288 Watts of light. This is assuming you are using 90* C wire, not 105* C automotive wire, if you are using 105* C auto wire, the load rates are higher.

As for using with the high beam lead, unless you don't use Flash to pass, no problem with this. Aux lights should not be flashed on and off quick, as it will shorten the life of the bulb. If you do use flash to pass, and you don't want to shorten the life cycle, just put them on a seperate switch in the cab of the truck. If you don't use FTP, or don't care that much, just connect the power from the relay coil to the high beam lead.

Aside form that, I assume you are good with wiring the lights up. If you go larger ( 10 AWG wire, 40 AMP relay ) you will be fine, just spending too much money on the project.

Good luck.