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Technical Headlight Relays??

Discussion in 'The Hokey Ass Message Board' started by jaw22w, Dec 25, 2019.

  1. Halfdozen
    Joined: Mar 8, 2008
    Posts: 612

    Halfdozen
    ALLIANCE MEMBER

    Rusty, thanks for this. I didn't know of Daniel Stern's website before, lots of good info there, and a source for quality parts.
     
  2. Brand Apart
    Joined: Jan 22, 2011
    Posts: 726

    Brand Apart
    Member
    from Roswell GA

    Bosch & Hella for sure
     
    olscrounger and Atwater Mike like this.
  3. Dirty Dug
    Joined: Jan 11, 2003
    Posts: 3,663

    Dirty Dug
    Member

    I've never used a headlight relay and never had a problem.
     
    sawbuck likes this.
  4. sawbuck
    Joined: Oct 14, 2006
    Posts: 1,873

    sawbuck
    Member
    from 06492 ct

    same here after reading this thread i was convinced i need em?
     
  5. jaw22w
    Joined: Mar 2, 2013
    Posts: 1,122

    jaw22w
    Member
    from Indiana

    If you want the best lights you can get, then you do need them.
     
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  6. G-son
    Joined: Dec 19, 2012
    Posts: 690

    G-son
    Member
    from Sweden

    Well... There are problems and there are PROBLEMS. Systems without relays have worked for ages, and as long as they work as they should they can work well - they just (generally) cause a bit more resistance due to the longer wires, more connections and so on along the way. This reduces the voltage that reaches the lamps, and reduce the light output (as well as it makes the lamps last longer).

    If you see good enough despite the voltage drop you are likely to have in such a system you don't ha ve a problem. You have less light than you could have, but if you don't miss the extra light it doesn't qualify as a problem. Perhaps you only drive in daylight?
    On the other hand, if you drive at night and would like to see better, any voltage drop between generator/battery and headlights IS a problem, as it reduces the light output.

    It takes a few minutes to start the car, measure the voltage at the battery after a moment (when it has stabilized after the load of starting the engine), and then measuring the voltage at one of the headlight lamps - straight ON the lamp connectors, with it still installed. Any voltage difference tells you you are loosing light.

    Then, the PROBLEMS... They often come with a burnt smell. They're kind of obvious, when something has gone wrong.
     
  7. Truck64
    Joined: Oct 18, 2015
    Posts: 4,230

    Truck64
    Member
    from Ioway

    Headlights are super sensitive to any voltage drop in terms of lumens or bulb output. It falls off a cliff with even just a few tenths drop in the wiring, connections, or grounds. So if you restore the grounds and connections you'll see much better. The same is also true for ignition and accessories, though not as noticeable as lighting.

    The first thing most people do is install a set of halogen bulbs, which aren't any better without the juice they need. If the grounds and cables and frame connections (and generator output) are within spec the lighting will be acceptable. Adding relays will take the load off the switch and improve lighting. I didn't notice a dramatic difference adding relays in terms of distance, probably because everything was already squared away, what I did find was there most definitely increased lighting to the sides. Road signs and markings are lit up better. It also seems to improve the tendency for generator equipped vehicles to dim somewhat at idle or just off idle. Generator systems are different from alternators in that the battery is the sole provider for juice at idle.
     
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  8. JerryTball
    Joined: Dec 2, 2020
    Posts: 20

    JerryTball

    Greetings guys and gals, as indicated in my profile I’m new to older cars wish I knew more about mechanics and how to work on them, i’ll learn, I’ve had like 20 Harley Davidson‘s 40 cars so I’ve worked on small things maintenance but when it gets into electrical and installing gauges and motor parts That’s where I don’t trust myself at all. I know this is an old thread but my question is, this car that I bought although it’s a 1940 street rod business coupe, the build is only about 9000 miles old originally were not originally but the motor that was put in at 9000 miles ago was a new 350 crate V-8 has a three speed Automatic transmission, all the lights seem to work on it it has a CD AM/FM 4 speaker stereo in it, end up front it has the 7 inch sealed beam headlights, the only thing that seems to work a little slow or the windshield wipers and that’s an easy enough fix from what my son told me. My question is I wanted to do something very simple that I can do it looks like I could just take a aftermarket 7 inch halo light for instance that has just one plug on it that would plug directly into where the current sealed beam is and everything would work. that said with this being a modern build would you think there’s any reason to add anything different to the car if I added those lights it’s a 12 V system of course alternator air conditioning fuel cell electric fuel pump.
     
  9. Happydaze
    Joined: Aug 21, 2009
    Posts: 1,035

    Happydaze
    ALLIANCE MEMBER

    I have a related question about relays if I may. The question concerns positioning of the relay(s). Does this matter at all? Logically I'd say no, the electrical current won't know where the relay is, but would welcome advise. Looking at say a '32, I'd prefer the headlite relay(s) to be hidden somewhere, ideally under the dash, such that the wiring looks as normal as possible plus the problem of trying to hide the relay(s) somewhere in the grille shell area is eliminated. Similar concerns with fan relay (non trad) and even fuel pump. In the headlite example I realise there would need to be 2 heavy feed wires (hi/lo) instead of just one (to relay) if the relay was in the grille shell or thereabouts. Thought?

    Chris
     
  10. Doublepumper
    Joined: Jun 26, 2016
    Posts: 693

    Doublepumper
    Member

    Headlight relay on my '46.....I have an alternator;)
    hlrelay.jpg
     
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  11. G-son
    Joined: Dec 19, 2012
    Posts: 690

    G-son
    Member
    from Sweden

    A protected location is always good, water and dirt isn't good for anything electrical. Other than that it shouldn't be anything but the basic common sense: the longer wires you need to use, the more resistance there will be in them and the bigger the voltage loss will be.
     
  12. Mr T body
    Joined: Nov 2, 2005
    Posts: 2,165

    Mr T body
    Alliance Vendor
    from SoCal

    Came up with this for the '32 a couple years ago
    [​IMG]
     
  13. When I changed my lights from standard seal beam to halogen I had to add relays to power the lights. Otherwise the GM type switch could not handle the load and the lights would switch on and off while driving.
    On my 32 I put the headlight relays up under the dash, not far from the headlight switch. I have one feed wire from fuse panel to feed both hi and lo relays.
    My fan relay is on my electric panel behind the seat. My carter electric pump only draws four amps, so it has no relay. Just a 30 amp toggle switch that I use to prime the carb.

    Hope this helps.
    Phil
     
  14. Just a note, I am using a mid 1960's Volkswagen locking relay for a dimmer switch. It looks like a Bosch relay, but each time it is grounded it switches between low beam relay and high beam relay.
    I can provide part number and wiring details to anyone who messages me.
     
  15. JerryTball
    Joined: Dec 2, 2020
    Posts: 20

    JerryTball

    Thank you I think I’m gonna leave the sealed beam headlights and place the bumper on the front of my car was removed so the local stereo shop that has been around for 30 years and I’ve done all my lights and window tinting and stereo stuff I got a put 25 inch LED headlights were those holes for the bumper was so I’m sure they’re just gonna wire that separately that she looked pretty cool I got a hole in the dash right for a switch thanks
    [​IMG]


    Sent from my iPhone using H.A.M.B.
     
  16. JerryTball
    Joined: Dec 2, 2020
    Posts: 20

    JerryTball

    2 5 inch not 25


    Sent from my iPhone using H.A.M.B.
     
  17. dalesnyder
    Joined: Feb 6, 2008
    Posts: 413

    dalesnyder
    Member

    I
    I don't understand the function of the first relay. Wouldn't the circuit work with just the second relay?
     
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  18. larry k
    Joined: Feb 23, 2009
    Posts: 340

    larry k
    Member

    They sell a 30 amp Bosch relay with 12inch pig tail and has a fuse in each one, I use "em" a lot !!!
     
  19. 1oldtimer
    Joined: Aug 21, 2003
    Posts: 7,676

    1oldtimer
    ALLIANCE MEMBER

    I used old Standard Ignition LR 34 on my cars. Just don't tighten the cover screw too much, it will pull up on the point block.
    [​IMG]
     
  20. FityFive
    Joined: Aug 9, 2010
    Posts: 309

    FityFive
    Member

    Do you have a part number?
     
  21. G-son
    Joined: Dec 19, 2012
    Posts: 690

    G-son
    Member
    from Sweden

    One relay for on/off, the other for hi/lo.
     
  22. 2OLD2FAST
    Joined: Feb 3, 2010
    Posts: 2,867

    2OLD2FAST
    Member
    from illinois

    Since the use of a relay is to restore the voltage lost with wiring and switches , wouldn't it be advantageous to locate the relay as close as possible to the load ? Seems to me that they used to be mounted to the radiator support ??
     
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  23. Wrench97
    Joined: Jan 29, 2020
    Posts: 240

    Wrench97

    The purpose of the relay in this case is lighten the load on the switch, hanging them o the radiator support you would want to switch to sealed or water proof relays.
     
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  24. Automotive Stud
    Joined: Sep 26, 2004
    Posts: 4,145

    Automotive Stud
    Member

    I have an o/t '60's car, it didn't even have halogen lights and the lights would sometimes flicker at night due to the headlight switch overloading. I put two relays on the radiator support but behind the headlight out of the weather, and upgraded to halogens at the same time. Best thing I ever did to that car.
     
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  25. lake_harley
    Joined: Jun 4, 2017
    Posts: 1,180

    lake_harley
    Member

    This is from back a few posts, but I have the same question.

    Lynn
     
  26. TrailerTrashToo
    Joined: Jun 20, 2018
    Posts: 776

    TrailerTrashToo
    ALLIANCE MEMBER

    If you use 12 Gauge wire for ALL the replacement wiring, the wiring voltage drop is minimized and the relay location is not important (see above comments about weatherproofing).

    EDIT: See the post below this post - The wiring diagram summarizes the above discussions - One criticism - The 50 Amp fuse is to big for 20 Gauge wire - A 20 Amp fuse (25 Amp maximum) for this wire gauge.
     
    Last edited: Dec 12, 2020
  27. Joe H
    Joined: Feb 10, 2008
    Posts: 965

    Joe H
    Member

    For relays to be effect, the power source must come right off battery and be a heavy wire. The longer the wires, the heavier they need to be. The dimmer switch turns relays on and off suppling the head lights with direct from battery power. Headlamps should also have a dedicated ground wire to battery or frame, not sheet metal. Headlight relays.jpg
     
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  28. lake_harley
    Joined: Jun 4, 2017
    Posts: 1,180

    lake_harley
    Member

    ^^^^That wiring diagram and plan make a lot more sense to me.

    Lynn
     
  29. TrailerTrashToo
    Joined: Jun 20, 2018
    Posts: 776

    TrailerTrashToo
    ALLIANCE MEMBER

    A 50 Amp fuse is too big for 12 Gauge wire - a 20 Amp fuse is better - maybe 25 Amps maximum.
     
  30. Wrench97
    Joined: Jan 29, 2020
    Posts: 240

    Wrench97

    A 6014 bulb draws 3.5 amp why would you possibley use a 50 amp fuse or 12ga wire?
    Factory setups use 10 amp fuses for headlights
    Why use 2 relays when the 5 prong relay was designed to be a hi/low beam relay in the first place?
    There is not a lot of draw on these circuits the most common issues are poor connections and old headlight switches with poor internal connections.
    I believe the original op just wants to move the dimmer switch up to the dash and use the blue internally illuminated switch, unfortunately the switch does not have the amp capacity for the the circuit without using a relay as a buffer.
     

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