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Technical Headlight rheostat, any fix?

Discussion in 'The Hokey Ass Message Board' started by Bird man, Nov 15, 2024.

  1. Bird man
    Joined: Dec 28, 2009
    Posts: 956

    Bird man
    Member
    from Milwaukee

    For the late 50's GM cars, some re-pops are available but they are pricey.
    Has anyone found a good solution for these? A new rivet search was fruitless, maybe find new resistor wire & cement it in with muffler cement?
    If someone could repair these, the clientele is there. And soldering just seems like a crappy solution. Looking to restore, not jury rig.
    Thanks! IMG_1685.JPG
     
  2. The labor cost for someone to repair a 70+ year old switch would probably exceed the 40 or so bucks that the new switches are going for. If it was me, 45 dollars for a new part is a better value than investing hours of my life looking for a solution that might not even work. But that's just my opinion.
     
  3. goldmountain
    Joined: Jun 12, 2016
    Posts: 4,654

    goldmountain

    Replace it with a new headlight switch.
     
  4. Try spraying it with DeOxit Gold contact cleaner. Most guitar shops should have some.
     
  5. Bird man
    Joined: Dec 28, 2009
    Posts: 956

    Bird man
    Member
    from Milwaukee

    NOS are $200-400.
     
  6. Budget36 and Johnny Gee like this.
  7. partsdawg
    Joined: Feb 12, 2006
    Posts: 3,628

    partsdawg
    ALLIANCE MEMBER
    from Minnesota

    No guarantee a NOS one will be better than a used one. Any electrical parts that have sat around for 70+ years through hot/cold cycles and perhaps stored in less than ideal conditions...wet or damp for example, may have issues
     
  8. Mr48chev
    Joined: Dec 28, 2007
    Posts: 34,847

    Mr48chev
    ALLIANCE MEMBER

    A standard DS156 fits a good number of 58/64 GM vehicles and sells for 59.79 on Rock Auto but should be available in a lot of places.
    Fist thing I would do is look my car up on Rock auto or if it is a Chevy check on the filling station https://www.fillingstation.com/ and see if a new switch can be had. Or buy the cheap switch from the filling station, spend ten hours piddle assing around switching the resistor to the "original switch and think you cut a fat hog in the process. Screenshot (1592).png Screenshot (1593).png
     
    '51 Norm likes this.
  9. Problem is if you look real close at the picture he posted the 2nd coil up from the left side is broken (chunk missing).
     
    Budget36 likes this.
  10. Budget36
    Joined: Nov 29, 2014
    Posts: 14,441

    Budget36
    Member

    ^^^^^ I see it. Snip it to the first good coil and use the “new” end under the screw.
     
  11. '29 Gizmo
    Joined: Nov 6, 2022
    Posts: 989

    '29 Gizmo
    Member
    from UK

    Well spotted. It looks melted so it could be Pulling too much current in that position. Either a dead short happened or too much bulb load.
     
  12. d2_willys
    Joined: Sep 8, 2007
    Posts: 4,317

    d2_willys
    Member
    from Kansas

    The problem with these rheostats is that they are used to carry bulb current and will get hot when set somewhere other than full on. I plan on using the rheostat to adjust duty cycle of a circuit that will drive bulbs or LEDS. Only about $2.00 worth of parts to do the circuit and only a few milamps of current through rheostat, meaning very little heat if any.
     
    G-son likes this.
  13. does anyone really run the dash lights at less than full bright? How about connecting the dash lights to the tail light terminal.

    "I see it. Snip it to the first good coil and use the “new” end under the screw."
    That would be good but it looks like the coil is bedded into the ceramic, don't know if he could dig it out.
     
  14. nrgwizard
    Joined: Aug 18, 2006
    Posts: 2,786

    nrgwizard
    Member
    from Minn. uSA

    "does anyone really run the dash lights at less than full bright?"

    Why, yes, yes I do. When in a large city at night, sometimes I'll dial them up to full, due to the large amount of fake-"daylight" surrounding the car & entering into it(but of course, not enough to read the gauges), but usually leave them on the low(er) end of the spectrum, esp when on a hiway or 2-lane. Night vision effect(s) have become a problem for me. I need just enough light from the gauges to read them, not read by them.

    & we won't get into miss-aligned headlights, esp the nice extra-bright ones... (& just where the F did I put those old WWII aircraft landing lights I was going to use in place of the fog/driving lamps???).

    Sadly, no-one makes/reproduces the red-night-lights(Stude Avanti "63->''64) that don't affect night vision, nor esp the ever-cool-&-incredibly-useful circa '46->'51 Studebaker UV-back-lit-"glow-in-the-dark" dash gauges. Chrysler used the Electro-Luminescent gauges in the mid '50s for awhile(similar effect, but more complicated & expensive). Much less in aftermarket gauges n lighting. Just old useless WWII technology that actually worked & was useful.

    Oh, well... ;( .

    Marcus...
     
    46international, Bird man and lostone like this.
  15. Joe H
    Joined: Feb 10, 2008
    Posts: 1,664

    Joe H
    Member

  16. Bird man
    Joined: Dec 28, 2009
    Posts: 956

    Bird man
    Member
    from Milwaukee

    Seen the Caddy Daddy repops @ $100+.
    57-59 GM cars excepting the Chevys used a quite different switch. and the rheostat thing is a problem.
    NOS is rare & expensive.
    Thanks guys!
     
  17. goldmountain
    Joined: Jun 12, 2016
    Posts: 4,654

    goldmountain

    Is there anything special on your headlight switch? As far as I know, most are very similar. Pull out one notch for parklights, two for headlights, turn the knob for courtesy lights and dimming dash lights. Push the knob on the side to pull off the knob to access the mounting nut. Replace with a later affordable switch and keep your old knob so that things look right. Maybe take a picture to show us what you have.
     
    46international and Budget36 like this.
  18. Ebbsspeed
    Joined: Nov 11, 2005
    Posts: 6,352

    Ebbsspeed
    ALLIANCE MEMBER

    Will you be using the dimmer resistor as a potentiometer, or a rheostat? Note that the voltage drop across a rheostat (variable resistor) is dependent on the current through it. Since it sounds like you will be running just a few milliamps through it you may not get the voltage drop you want, even at the highest resistance setting.

    You can turn that rheostat into a potentiometer (voltage divider) by grounding one end of it. Then you will have available the full range of voltage (0 to 12) to control your circuitry.
     
    d2_willys likes this.
  19. G-son
    Joined: Dec 19, 2012
    Posts: 1,417

    G-son
    Member
    from Sweden

    Well... It would probably burn up if you ground it directly. It's meant to feed some small light bulbs, meaning they limit the max possible current. Could of course replace them with a suitable resistor, and use the voltage over that to control the electronic regulator - but it would increase the current over a few milliamps if you want sensible voltage levels to work with.
     
    Ebbsspeed likes this.
  20. You could run a wire from your tail light terminal to an external potentiometer and then to your dash lights. Mount the potentiometer under the dash (or on it if you like). You will have to have a wirewound potentiometer. that can handle the power. If you can measure the current going through the dashlight circuit at full voltage, you can calculate how many watts the pot should be.
    Or you can replace the incandescent bulbs with LED's, and if they need dimming, insert a resistor and a 2 way switch in the circuit so you can have a "bright" (no resistor) or "dim" (through a resistor) setting.
     
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  21. d2_willys
    Joined: Sep 8, 2007
    Posts: 4,317

    d2_willys
    Member
    from Kansas

    The rheostat in my circuit doesn't control voltage, only duty cycle, which then controls the average voltage at the light bulbs or LEDS. It doesn't matter about current being drawn through rheostat, only that the rheostat can change the duty cycle. Simply put, the circuit is a triangle wave generator followed by a voltage comparator. The rheostat sets the threshold of the comparator. The comparator output is used to drive a transistor, which is used to drive the bulbs or LEDS.
    Oh, BTW, the circuit can be used on 6 or 12 volt systems, negative or positive ground.
     
    Last edited: Nov 18, 2024
  22. G-son
    Joined: Dec 19, 2012
    Posts: 1,417

    G-son
    Member
    from Sweden

    Yes, but when you use that rheostat as a potentiometer the low resistance of it may be an issue. If it's meant to drop the voltage to the instrument lamps for example 6V at 2A that means it has a resistance of 6V/2A=3 ohm. Fictional numbers, but just something to work with now.
    If you just run 2mA through it in your circuit (using another series resistor to limit current, and probably a regulated voltage as a source to get a stable input and output voltage) you get a whopping 0.006V across it at maximum resistance, and hopefully 0V at minimum setting. 6 millivolts difference from minimum to maximum isn't much for a comparator to work with - interference from the ignition system etc. will probably be far bigger than that.

    A small current through a small resistance means a very small voltage. It can be done, but it seems impractical. A bigger current would give a bigger voltage difference that would be easier to work with.

    Would be interesting to see a schematic of the circuit you have in mind.
     
  23. In_The_Pink
    Joined: Jan 9, 2010
    Posts: 788

    In_The_Pink
    Member

    pprather likes this.
  24. d2_willys
    Joined: Sep 8, 2007
    Posts: 4,317

    d2_willys
    Member
    from Kansas

    You run a gain stage to boost the voltage through rheostat. Then the comparator will have enough to do the job.
     
  25. d2_willys
    Joined: Sep 8, 2007
    Posts: 4,317

    d2_willys
    Member
    from Kansas

    Probably going to use an LM324 to do all of the work.
     
  26. Kevin Lee
    Joined: Nov 12, 2001
    Posts: 7,622

    Kevin Lee
    Super Moderator
    Staff Member

    After burning out two of those turds within a week I ran all of my 6V gauges and lights in the F1 for years and years through a solid state voltage reducer. Found it on ebay. Big aluminum heat sink and the output was controlled by a small knob with an LED readout – "X.X" for output voltage. Set the output to something like 6.8V and everything was rock solid. All hidden under the dash next to the fuse panel. Throw that thing in the trash
     
  27. G-son
    Joined: Dec 19, 2012
    Posts: 1,417

    G-son
    Member
    from Sweden

    That probably works, but I think you need to stick with a fairly low gain to avoid problems with interference. Would be somewhat annoying to have the instrument lights start flashing once the spark plugs are getting worn. Although I suppose it can be used a service reminder! ;)
     
  28. d2_willys
    Joined: Sep 8, 2007
    Posts: 4,317

    d2_willys
    Member
    from Kansas

    A simple low pass filter for the gain stage will cancel noise out.
     
  29. d2_willys
    Joined: Sep 8, 2007
    Posts: 4,317

    d2_willys
    Member
    from Kansas

    Next up is to get one of the dimmer rheostats and find out what the actual resistance is across the total range.
     
  30. Damon777
    Joined: Jan 7, 2022
    Posts: 80

    Damon777
    Member

    I ended up fixing the one in my 50 Buick with solder, but it was just the end that was broken. I was more in there to get the switch functionality back. Turn for full bright, next detent for map lights. All the way down has another detent to turn everything off. It works, but still has a dead spot or two. It doesn't really matter, as the way the lights illuminate the gauges everything but the speedo is a challenge to read even at full bright.
     

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