Technical Is a headlight relay needed or a 6/12v conversion?

I am converting my fifty Chevy to 12 volts. I will have little amperage demand. I don't use even a radio. I will have my generator converted to 12v by a local shop. Has any one used vintage Auto Garage for electrical parts? The sale of conversion kits is heavily marketed by them. They recommend a headlight relay for this conversion. I am asking if this is needed, because I have never heard mention of a headlight relay while have 12v conversion conversations with other guys..
http://www.vintageautogarage.com/Headlight-Relay-12-Volt-Kit-p/rlk-1.htm

 

Short answer: No. 12v puts less load on wiring and switches than 6v. Maybe if your wiring and switches are tired or you replace them with undersized cheap 12v items but usually, not necessary. You might ask them why they think their conversion needs a relay.

 

if your wiring and switches are in good shape you should have no problem

i have never used a relay for the headlights on any car i have built

 

It's trendy to run relays on everything, some companies have figured out that selling relay kits is a good income source.

 

Bingo.....

 

If you open the link I provided, you can read their explanation. The say this relay will keep the headlights from going dim to bright and bright to dim.

 

Exactly! That is why I am seeking opinion from you guys who have already did this job. Another example is Patrick's antique auto in Arizona. For decades he has recommend generator conversion for guys like me who have little amperage demand, and want to keep aesthetics period perfect. Now, since Patrick is selling conversion kits including a alternator, he has rescinded his decades long recommendation! Has anybody had experience with vintage auto garage?

 

There's only two reasons to use a relay rather than a switch to control something; one, the wire or system supplying the component is too small. And two, the switch rating is too low. If converting from 6 volt to 12 volt lights, you're cutting the current (amps) in half if the watt rating of the lamps are the same. If the 6 volt lamp is rated at 40 watts, you can use up to a 60 watt lamp at 12 volts and still not exceed the amps of the 6 volt lamp.

If your 6 volt headlights were working adequately, there's zero need for a relay....

 

Any voltage loss between battery (or generator) and the lightbulb causes a rather severe loss of light, lowering the voltage by 5% reduces the light output by approximately 20%. A "old style" wiring where the wiring to the lamp has a long way to go and p***es through manual switches and numerous connectors will always have bigger losses than a short wire going straight from the battery to the lamp with just a relay to control on/off.

Do you ever drive by night, so you use the lights to see, and more light would be better? Go the relay route, without a second thought.
Do you only drive in daylight, and want to avoid ANY change from the original look? Stay with the original wiring. Or put in the relay in a hidden spot, a bad light switch could get hot and potentially cause a fire - not something you want to happen under the dash! A relay is not completely immune to that sort of problems, but generally much lower risk.

 

I personally favor the alternator conversion. It pretty much eliminates any voltage fluctuations at low speed. I would also ditch the factory ammeter if equipped. Unless you are converting to HID headlamps you can forego adding headlamp relays.

 

I suppose your position of favoring alternator use is in the consensus. But I have made the decision to use my original generator. I know I will have plenty of opportunity to defend my decision in the future. Since I do not know what HID headlamps are, they have not entered my mind. They are probably modern and high tech, designed to distill the old car driving experience, which I intend to keep intact, in most regards. This old car is not often driven at night, so I will probably forego the headlamp relay. I can add it later if problems dictate that a solution is needed.

 

I can add it later if problems dictate that a solution is needed.

 

I always thought that using a relay helped reduce the wear on the OEM headlight switch contacts.
I converted my 40 Ford to 12V with halogen headlights and used one relay connected to the
floorboard dimmer switch. I have also been told that it's best to install the relay as close
to the headlights as possible. Works fine.

 

Do you have an opinion on a a headlight relay, or find fault with my decision to install one if problems develop? Or did you find an opportune time to use a cute, juvenile post sticker?

 

I got a chuckle from it. Relax.

 

Very interesting Fordy. I was wondering about the function of the floor dimmer switch when using 12v. I will ask manufacture about the placement of the relay. Do you recommend the use of 2 relays, one at the dimmer switch, and another close to headlights? I am going to ***ume you are using the relay for ***urance against potential damage to the OEM headlight switch points. Did you open my vintage link and see if it it close to the appearance of the relay you used?

 

Well, I did too, I guess. I think he was inferring that if I had a fire, it would be too late for installing relay. From your post and others, you all have confirmed my su****ion that I don;t really need the relay. The future problems I was referring to was not having a consistent light beam, which could be rectified with relay installment..

 

That's not why a relay is usually installed. Read post 8, that's why relays are generally used. If you have a switch that is failing, you could extend it's life with a relay but that's not good practice. Good condition 6 volt wiring and switches will be oversized for the same load at 12 volts.

 

If you're referring to the lights brightening and dimming at idle or low speeds, that's caused by the charging system regulator and a relay won't help with that. That's a fairly common problem on generator systems because they don't charge well (or at all) at low speeds, which is a big reason they were replaced with alternators.

 

My 6 volt headlights work adequately. The original wiring in my 50 is in very good shape.

 

The man trying to sell me the relay conjured up that problem. I am fully aware of the lose of charging capacity at low speeds. I will continue to deal with that. Here is the statement the vendor is using to justify the sell:
Headlight relay kit comes with 12 volt relay and connector with set of instruction how to add relay to
most cars and trucks to remove the high current from the headlight switch which is the cause of dim headlights
in older vehicles.

 

Then there's no need for a relay. If you do a straight swap for another sealed-beam lamp, the current will be half of what you have on 6 volts.

 

Yes I've used them in cars from the 60's on 12volt changing over from sealed beam to halogen which is a must. But even using the relay with sealed beams made a hell of an improvement. If you've ever driven in Australia with the kangaroos on our ****** terrible roads you need as much light as you can get without compromising the original looks.

Sent from me to you using the HAMB mobile app

 

That's an issue on cars with four headlights, not two. On a four-light system, the OEM high beams are actually a lower wattage compared to the lows, but there's four of them. Modern halogen replacements have a higher high-beam wattage, so on high beam you'll find that the wire size can be too small, and more importantly, the internal circuit breaker in most switches will prove to be too small. Not cool to have all your headlights go out when on high beam...
So relays are used to 'fix' this. Not needed on two-light cars if the wiring is in good condition and adequately sized.

 

i use minimum 12 gauge from the fuse to the headlight switch to the dimmer switch. then i run minimum 14 gauge separate wires from the dimmer to each high and low of both headlight bulbs..so there are 5 wires on my dimmer switch. i do not use a junction block and i have never had a problem

 

Thanks for the responses fellows. The above quoted replies are the kind I like to get. I can ponder them and understand, and then have a good basis to make my decision. I like to learn form the experienced, who are committed to help the inexperienced.

 

You might want to give this a read,click on "A current topic" http://www.watsons-streetworks.com/tips Since most replacement headlight bulbs are now halogen when I converted to 12 volts the output was very dim and this was with a 100 Amp alternator,Fry's Electronics have the relays and harnesses so got them there and WOW! what a difference it made.

 

Interesting, I can see just fine at night in my new Edsel, 4 headlights and still has all the original wiring and generator. My wife's 70 dart is the only car we have with dim headlights, it has an alternator that can't keep up at idle.

 

Yes, I looked at your Vintage link. That relay looks just like the one I used. Here is the same relay much less expensive.
https://www.carltonbates.com/Genera...e-Relay-40A-SPDT/RC-400112-RN/p/63285063018-1
As I said, I used only 1 relay for both halogen 12V headlights. I did not use 2 relays. I mounted the relay on the left hand frame rail inside the engine compartment as that was closest to the lights and also easy to install there.

Attached Files:

 

Here's the relay for running both headlight off of ONE relay.