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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: 606


    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: 678

    Brand Apart
    from Roswell GA

    Bosch & Hella for sure
  3. Dirty Dug
    Joined: Jan 11, 2003
    Posts: 3,653

    Dirty Dug

    I've never used a headlight relay and never had a problem.
    sawbuck likes this.
  4. sawbuck
    Joined: Oct 14, 2006
    Posts: 1,872

    from 06492 ct

    same here after reading this thread i was convinced i need em?
  5. jaw22w
    Joined: Mar 2, 2013
    Posts: 1,064

    from Indiana

    If you want the best lights you can get, then you do need them.
  6. G-son
    Joined: Dec 19, 2012
    Posts: 664

    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: 4,142

    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.
    G-son likes this.

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