Anybody know the safe limits in terms of adding a load on the high beam lead?

[EDWARDCASE]

I want to add a 4.3 amp LED light bar and use the existing lead to the high beam side of the bulbs. Will the wiring going to the high beams handle this additional load? i dont want to run a separate wire and fuse and want to avoid doing a separate relay unless i really have to.

 

[donalds]

No they will burn up imo

 

[allmyEXes]

I would trigger them off of your driving light circuit however use a relay for safe measure. It would take less time to install a relay than to unwrap and repair melted wiring from an overload or worse think about this. You wired your additional lights to your headlight circuit, overload it and burn up the headlamp switch. It's very dark and raining. Now how are you going to see to get home. I know what I would do.

 

[96eb96]

I want to add a 4.3 amp LED light bar and use the existing lead to the high beam side of the bulbs. Will the wiring going to the high beams handle this additional load? i dont want to run a separate wire and fuse and want to avoid doing a separate relay unless i really have to.

Measure the voltage drop across one highbeam.

I would trigger them off of your driving light circuit however use a relay for safe measure. It would take less time to install a relay than to unwrap and repair melted wiring from an overload or worse think about this. You wired your additional lights to your headlight circuit, overload it and burn up the headlamp switch. It's very dark and raining. Now how are you going to see to get home. I know what I would do.

The original owner on mine put PIAA lamps wired off the battery and its own switch thru a relay.
But the driving lights (or highs) should suffice to drive a relay. It is in the milliamp range. If you are going to make wiring modifications, at least do it right. The wires were engineered to barely carry the highbeam current, obviously to save cost.

 

[410Fortune]

use a relay otherwise you will melt connectors at the high beam relays or multifunction switch or more

 

[J_C]

Besides what others have mentioned, I don't see the purpose of tying this into your high beams. High beams are legal for public road use. LED light bars are not.

If you tapped off the high beam supply and still added a switch to control the LED light bar so it can still be kept off when high beams are on for road use, this does not seem to have any advantage over wiring independent of the headlights, would be about as much work too once you have to splice into that.

It has the disadvantage that we have no way of knowing how much current the Multi-Function Switch can handle. In brand new condition it is just acceptable for headlights, but as it ages (or replaced with a generic Chinese one) the copper contacts corrode, grease hardens, internal resistance rises, so if you do wire to the headlight circuit anyway, then I would at least open your MFS and clean the contacts or else you may melt it from the additional current.

At only 4.3 amps, you are still within a comfortable margin where you don't necessarily even need a relay (to just wire it direct, not through the MFS). You could run battery positive-fuse(immediately after battery)-light bar-ground return wire to cabin where a switch is in series with a good chassis ground. This leaves your existing wiring 100% stock. Just make sure to pick a switch that is rated for plenty of DC current. DC needs more robust contacts to survive arching.

Odds are that your light bar has a buck switching circuit inside of it, so itself is not very sensitive to voltage drop like an incan bulb is, but for mechanical fortitude I'd still use at least 18ga or lower wire.

However, if this is a generic Chinese light bar, and you haven't measured the current yourself, it could be lower than what they claim. Often the generics use 3W, 5W, or even 10W LEDs, multiply the number of them to tell you a wattage, then divide that by 12V to tell you current, but the circuit usually doesn't run the LEDs at full power because the enclosure has insufficient heatsinking to handle that much heat, and because your higher 14.(n)V system with alternator operating, should result in lower current to the LED bar circuit than if it were at 12.0V.

 

[C420sailor]

Run a separate switch. There are likely going to be times you’re going to want the bar on without turning the vehicle lights on.

 

[Craigerz]

I used my factory fog light wiring and switch. The wiring is already there. The switch is already in place and looks clean. There is a mod on here you can do that keeps the fog lights on when the high beams are on. So my spot lights can be turned off and on when on the highway and not, and they stay on on low/high beam. Don't know if 4.3 amps is too much for it.

But, they cannot be turned on when the lights are not on.

 

[donalds]

12 Volts

4.583 Amps

55 Watts

Per fog light
Why not use the fog light circuit to power the relay 250ma
You don't want

 

[toypaseo]

On my 96, I did the wiring mod where the factory driving lights can be on, as long as the vehicle is on, via the OEM dash switch. I discussed the idea with @Turdle, and he said the Rigid Industries LED bar I was going to use would pull less current than the OEM driving light bulb. Here is the light mounted in the OEM light bracket.

 

[allmyEXes]

@toypaseo Nice! I like that upgrade and would like to do that to my '97. IYDMMA (If you don't mind me asking) where did you purchase those?
EDIT I found those on Ebay. Very Nice!
I also found these and wonder is the driving light socket H1 and are these within the factory amperage limitations? Replacement LED driving light bulbs
@EDWARDCASE Excuse me if I hijacked your post.

 

[EDWARDCASE]

High beams are legal for public road use. LED light bars are not.

i only use the high beams here on country roads after most traffic is done, a lot of people use LED bars to see the deer before they jump in the road. I am not worried about the legalities here because i know the town cops and state troopers here. better safe than dead.

 

[EDWARDCASE]

The wires were engineered to barely carry the highbeam current, obviously to save cost.

i was hoping somebody might know if there is just enough room for the 4.3 amps. sometimes engineers have to bite the bullet and size up to the next wire size because the smaller wire just wont handle it, but the next size wire might have the room amp wise. Not every wire is maxed out in everry circuit. i just am looking to avoid the delay of a relay combined with delay of an led bar.

 

[donalds]

When you install them be sure to post pictures of the burnt wires so we can show the next guy proof

 

[EDWARDCASE]

Run a separate switch. There are likely going to be times you’re going to want the bar on without turning the vehicle lights on.

i am actually installing additional front sides and rear lights. i just want that easily switchable bar using the mfs. i might wire in an additional hot just to turn it on separately.

 

[EDWARDCASE]

When you install them be sure to post pictures of the burnt wires so we can show the next guy proof

sorry to burst your bubble, i wont have burn wires because i am doing the research before hand. i will probably get everything wired up and run a switched setup for now and have my friends kid calculate the loads to see if i can do what my original plan was.

 

[EDWARDCASE]

I used my factory fog light wiring and switch. The wiring is already there. The switch is already in place and looks clean. There is a mod on here you can do that keeps the fog lights on when the high beams are on. So my spot lights can be turned off and on when on the highway and not, and they stay on on low/high beam. Don't know if 4.3 amps is too much for it.

But, they cannot be turned on when the lights are not on.

i was toying with that idea but ended up getting some combination driving/fog lights that run separate circuits for each function, so i am reserving the foglight circuit for driving lights and will wire the fogs as a stand alone light so i could run amber fog lights with running lights but no head lights.

 

[donalds]

I would use a relay and fuse
I would use the fog light circuit to power up the relay
Run a fused power wire to your relay and the feed from the relay to power your lights
This will allow the fog light switch to turn on your leds and fogs

 

[J_C]

i am actually installing additional front sides and rear lights. i just want that easily switchable bar using the mfs. i might wire in an additional hot just to turn it on separately.

It is impossible for us to predict the state of your factory wiring and connectors on a now, ~23 year old vehicle. That is a significant factor, that could cause melted wires or connectors.

If it were not for that factor, the wiring as it were new, should handle the extra 4.3A, but would have additional voltage droop to the high beams, so your incan highbeams are dimmer than previously, so since your light bar is very unlikely to throw as far as the high beams (the long distance spot), adding the light bar to your high beam circuit with existing wiring is likely to decrease longer distance illumination provided by the high beams.

However you want it through the MFS. The only safe (non-gambling, unless you can talk to a Ford engineer with the current spec for the MFS and get a new Motorcraft one, AND clean all the oxidation out that has accumulated after 20 years of sitting on a shelf somewhere) way to power the light bar from the MFS is use the power to the high beams to trigger a relay. Even if you did replace or clean the MFS, another common fault is the connector to it gets hot, deforms and the wires pull out the back... so asking for any more current through the MFS (besides a few tens of mA to trigger a relay) is pushing it.

 

[C420sailor]

The problem isn’t so much the wiring gauge, it’s the state of the connections after 20+ years. Ford used these weird heat shrink crimps in their wiring, and they tend to corrode over time. That is what donalds is likely getting at.

Your wiring may be pristine and you may get away with it, or you may have one mildly corroded connection/termination in there that drives the resistance up...and you know how the rest of that story goes.

I’ll take a look at the wiring in my truck and see if I can determine the gauge. I have a headlight flasher installed in mine, and my high beam wiring is readily accessible...although I can’t remember if these high beams are positive or negative switched. I’ll take a look.