Headlight relay advise

[rcl700]

I'm planning out the re wiring in my car and want to run relays for hi, low, and fog lights. 

The question I have is, do I run one relay between the headlight switch and the light switch or one relay for hi and one for low after the dimmer switch? 

I was planning to run (3) relays hi, low and fog. My thinking was to place them somewhere close to the battery. 

 

What kind of setups are you all running?

Are 30A relays okay?

[DonaldSmith]

For my 47 DeSoto, I bought a vintaqge headlight relay - actually two relays under the same cover, one for the low beam and the other one for the high beam.  (I don't have fog lights.)  I can't answer if 30 amps are enough .   

[Sniper]

Over kill on amperage is ok when talking about relays.  I run 30A ones even though I have LED headlights, GE Nighthawks.

 

Not sure what headlights you are running, but current draw specs should be available whatever they are, just remember to double that number because you have two headlights.

 

The stock head lamps for a 48 Plymouth draw 8.6A on high, that is 17.2A for the pair.

 

If you have converted to 12V then it is 5A per bulb, 10A total.

 

Do not forget to to protect the circuit with a fuse or fusible link, maybe a self resetting circuit breaker.

 

 

 

 

[rcl700]

12 minutes ago, Sniper said:

Over kill on amperage is ok when talking about relays.  I run 30A ones even though I have LED headlights, GE Nighthawks.

 

Not sure what headlights you are running, but current draw specs should be available whatever they are, just remember to double that number because you have two headlights.

 

The stock head lamps for a 48 Plymouth draw 8.6A on high, that is 17.2A for the pair.

 

If you have converted to 12V then it is 5A per bulb, 10A total.

 

Do not forget to to protect the circuit with a fuse or fusible link, maybe a self resetting circuit breaker.

 

 

 

 

Everything I'm currently running is stock 6v pos ground. 

I'm hoping to lighten the load on the stock headlamp and dimmer switches, while getting better light output from the bulbs. 

So a relay for each is recommended?

 

Edited August 24, 2023 by rcl700

[maok]

You can buy relays with a fuse built into the relay case.

[Plymouthy Adams]

that is your call on one or two....many folks will power the dimmer switch through a relay controlled by the headlight switch as the wiring and dimmer switch can handle the current without problems....the dimmer switch is by design self cleaning.....

 

 

[D35 Torpedo]

Relays are not necessary and will just look ugly... but if you must...use the factory feed to switch the relays. Putting them close to the battery makes the most sense. I'm running 40/50 watt 6volt headlights with 12 and 10 gauge wire straight from the headlight switch. The factory headlight connectors can be desoldered and reused. 

[Sniper]

9 hours ago, D35 Torpedo said:

Relays are not necessary and will just look ugly.

 

I think I would disagree on the unnecessary part and they can be hidden if need be,  A simple voltage drop test will tell you the state of the circuit feeding the headlights.

[D35 Torpedo]

1 hour ago, Sniper said:

 

I think I would disagree on the unnecessary part and they can be hidden if need be,  A simple voltage drop test will tell you the state of the circuit feeding the headlights.

That's a good idea. I guess if the circuit is in shambles, a relay will be the easiest fix to get you rolling. What I mean is the original switch is plenty adaquate. You may need to replace the wire. 

[Plymouthy Adams]

while the switch is adequate when NEW....and serviceable after many years, the fact is, the brass plates inside are wearing and the thus the normal friction/tension on the contact is less these days and eventually like many here, you looking for a replacement switch one day.  Thus many folks not only here but hobby wide find the fitting of a relay(s) and removing the higher current that does not like high resistance in worn contacts...voltage drops and dimmer lighting, you end up extending the life of the switch many more useful years on the average with a better more positive switch that is the electromagnetic contacts in the relay.

 

Again, everyone can do as they wish, but there are legit reasons for some of these changes and why these relays are so prevalent in modern cars. 

[Johnboy]

I installed one relay for my headlights. Which works great, my headlight switch was getting too hot and would blow the fuse on the switch. I installed the relay in the drivers side kick panel, and ran a wire from the battery which is under my front seat with a inline fuse at the battery.

[junkers72]

I rewired my 47 DeSoto and kept it 6v positive ground . Added headlight relay that is 2 circuits . I put a fuse between feedwire and the unit has a fuse for each beam . Also put in 6 volt halogen headlight bulbs . Works well and I’m not afraid to drive it at night . As a bonus I added a relay for the brake light circuit.