Technical Hiding relays in headlight bucket

So I am wiring up my 39 ford truck 12v.
I am thinking it’s a good idea to hide the relays to keep the wiring and engine bay tidy.
I searched but found no information so my question is… can I put the headlight relays in the headlight? There is plenty of room in that big bucket. That way they are not hanging off the inner fender.

 

Find some way to secure them so they don’t flip about. Even double sided 3M tape

 

I did my core support junctions behind the head lamps (inside the bucket) on the avatar car.

 

On my rod the relays are up under the dash, not far from the headlight switch and dimmer switch.

 

From a standpoint of "keeping things tidy" with the relay in the bucket wouldn't you need to actually complicate the wiring, what with a solenoid trigger wire and a power wire for the headlights instead of hiding the relay closer to the switch and only routing the power wire to the buckets? What am I missing?

 

You shouldn't have a problem hiding them in the headlight bucket, the only drawback I would see is having to run the extra 12v supply lead to power the relays, then splicing the headlight harness for the control leads.

 

The reason you would place the relays closer to the headlights is so you do not have the voltage drop from the wire length, that way you actually have 12v at the headlights. The factory headlight wiring causes the voltage to drop 4-5 volts just due to the wire gauge ( usually 12 or 14 gauge) and length.
In most cases, the 12v power supply comes from the horn relay, or voltage regulator mounted on the radiator support/inner fender. That wire goes to the headlight switch for power, leaves the headlight switch to the dimmer switch, leaves the dimmer switch back to the headlights... all in the same harness.

 

If the wires for the headlight load are sized adequately you shouldn't have any voltage drop at around 12 ft. Cars have worked great for many decades and not had voltage drop in such a short run. If your headlight wiring is getting drops of 4-5 volts you've got something wrong with not just the wiring, but connections.
Headlights only draw about 4.5 amps, and most factory systems are fed with 14 ga. wire good for 15 amps. It would take a much longer run than 12 ft. to lose that much voltage.

 

As others have said, I'd hide the relays closer to the switch so that you're not complicating your system with extra wires running all the way to the headlights. Relays hidden under the floor in a waterproof box or under the dash simplify the front wiring harness to the lights.

As @1971BB427 said, the idea presented that you would have 4-5 volts drop in the wiring to your headlights indicates other issues in the system.

 

What lights are we talking about now, one right, one left, low beam and high beam? Anything more?

If there's room I see no problem with having relays in the headlight bucket(s). If it simplifies or complicates the wiring may depend on exactly what configuration we're talking about, and if you put relays on both sides or power both sides off the same relay(s).
Running both sides off the same relay is good for simplicity, while keeping as much as possible separated is good for redundancy - it's not a nice experience when you drive at night and all lights go out at once due to one single failure or blown fuse. Losing just one headlight while the other keeps working is far less problematic. On the other hand, if you never ever drive in the dark such redundancy may be overkill.

 

Relays made a Huge difference in my (M-word) hot rod!
I hide the relays ,one for high beams one for low beams, (horn too) in the battery tray area. I built a cover to go over it since I moved the battery to the trunk years ago. Light buckets would seem like a great place to put all the 'stuff' and give the engine compartment a tidier appearance .Which is what you're after.
6sally6

 

You need two relays on the headlight side of the dimmer switch. Along with brighter lights that is primarily to protect switches that aren't designed for higher amp halogen bulbs.
I had that problem with the floor mounted switch on my 71 GMC running H-4 Halogen bulbs. Burning out a dimmer switch every few months. Same exact switch (part number ) that I have on my 48.
The only issue is that you will have a separate hot all the time wire running to the headlight bucket that the relays are in.

 

So far I have 4 wires run down to each headlight from the firewall no wires across the front. I have 4 wires now high low park turn. Add a constant 12v supply to each side to run everything and also put the thermo fan relay in the headlight so that’s another 2 wires for that side then there is only the battery and start solenoid on the firewall and some wire loom running across the firewall and along both inner fenders

 

I wasn't saying that a 4-5 volts drop is normal. I am taking into account wire age, engine heat, wire length ,etc. can cause a voltage drop. Putting the relays closer to the headlights prevents this. I've seen 50's-60's restored cars with new high quality wiring harnesses, great output on generator or alternator, new switches, bulbs, etc. still have a voltage drop at the headlights around 2-3 volts. You'll have 13.4 v at the source, but 11.0 v at the headlight connector.

 

The other replies also reminded me, running circuit breakers in your headlight power circuit is a good idea. The reasoning is that you want your circuit breaker to trip, cool down, and then re-energize the lights rather than a fuse that just kills the lights altogether.

 

I ran my relays in the old voltage regulator. Never tell

 

Yes, it's just more and thicker wires running into the bucket.

Couple of ideas:
-You can weld a tab on the inside to attach the relay instead of running a bolt/screw through the housing.
-You can run cube style relays inside an old regulator housing, so it's less*****tastic looking.

 

Todd, if you have a 4-5 volt drop at your headlights, you have some other serious electrical problems. When I troubleshoot headlights I look for no more than 0.2 volts on the positive side and no more than 0.1 volts on the negative. That adds up to 0.3 volts total.

 

I was stating worse case scenario for a 60+ year old wiring system at a 4-5 volt drop. I apologize for not being more detailed in my original post. You are going to have more than .2 volts difference in potential (even on a brand new car) between the back of the alternator and the positive battery cable terminal at the battery. Most GM, Ford, Mopar cars and trucks built in the 1950's -1960's have several connectors in the harnesses. The fuse box, switches, bulb connectors, bulkhead connections at the firewall, etc. all add up causing resistance. The higher the resistance= higher amperage= lower voltage. Let me ask this simple question. If a .2 volt or .3 volt drop is normal between the alternator/generator and the headlight bulb connector, why would the original poster (ActionYobbo) need headlight relays? If his alternator output is 13.0 v... I promise you he is not going to see 12.7 volts at the headlights unless that is the only item on his truck he is supplying power to.

 

Putting the relays closer to the headlights doesn’t prevent voltage loss. Correctly sized wire from a correctly located source prevents voltage loss. Simply placing a relay in the headlight does nothing if not wired properly. If wired properly, the relay can be anywhere.

 

Would it be easier to make them more "serviceable" like under the dash? You still have the wire run from the switch to the relay.........What would you be saving?

 

The grounds to the head light buckets would be the first step to brighter lights. How are you going to ground the relay? Run another wire?

 

Here I thought one of the purposes of adding relays was so you could also upgrade the old wiring at the same time. I also thought the main reason to run the relays was to reduce the power load on the headlight switch and put it on the relays?

Having to pulling out the headlight to check the power to the relays when troubleshooting a no headlight satiation sure sounds like loads of fun too.

 

Very true.
You also present a good argument for having another set of running lights, fog lights, or parking lights controlled on a different circuit even if they are concealed behind a grill.

Any light is better than total darkness.

 

Agreed. Probably nearly as important as seeing is being seen. If you have a headlight circuit failure in the dark and can at least have your park lights on, people can see you.

 

You make a good point that relays, like fuses, should be accessible for easy replacement. Putting them in the headlight bucket sounds like a royal PITA.

 

A single clip to remove the headlight****embly sure sounds easier than climbing under the dash or taking the side panel off to get to the inner fender and with separately fused power to each side and separate relays for the lights if one light is out then it’s most likely the bulb anyway. No power to the light would be the fuse at the battery. No power to all lights would be the switch fuse

 

I don't usually go around messing with headlight buckets, but it does indeed sound like a nice place easy to access, possibly comfortably sitting down on something. Things hidden under the dash never seems to be easy to access, crawling around in the car, trying to see something up in there...

 

I just can't imagine having to run all the extra wires to the headlight buckets.

Not just labor wise but the added expense of instead of having a couple wires 2 ft long, now they are 12 ft long.

Not to mention adding extra size to the wiring loom which on mine I want hidden.

Also like the fact of no hot wires, especially higher load wires running that far forward other than when turned on. Also sounds like a major lot of work chasing that much wire forward if something should happen, like something getting kicked up off of the road, water intrusion, shorts, or even a small wreck...

I prefer keeping wires to a minimum, especially high load, keeping wires as short as possible and putting the relays in the buckets, too me, does just the opposite....

...

 

Yeah, more wires is more potential failure points. Plus if you do a relay for each headlight high and low you're adding a lot more wire.

It seems like extra work and expense for a lot more potential for issues to me.