Technical Headlight rheostat, any fix?

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!

 

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.

 

Replace it with a new headlight switch.

 

Try spraying it with DeOxit Gold contact cleaner. Most guitar shops should have some.

 

NOS are $200-400.

 

How about grabbing one out of another switch. Check other years to see what similar. I don't know what your application is but look at old aftermarket parts also.


Here's one from a Cadillac:


https://www.caddydaddy.com/1959-196...at-reproduction-free-shipping-in-the-usa.html

 

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

 

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.

 

Problem is if you look real close at the picture he posted the 2nd coil up from the left side is broken (chunk missing).

 

^^^^^ I see it. Snip it to the first good coil and use the “new” end under the screw.

 

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.

 

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.

 

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.

 

"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...

 

I solved my light issues with LED strip lights around the inside of each gauge pod and one of these https://www.ebay.com/itm/2853899040...4aw7eamkS9k49iqTl6SYMe4YSm1x|tkp:BFBMqqPK1eZk dimmer switches.

 

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!

 

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.

 

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.

 

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.

 

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.

 

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.

 

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.

 

Maybe not 100% applicable to this particular application, but related, and might prove useful for someone: https://www.onallcylinders.com/2023...ht-switches-and-how-to-clean-or-repair-yours/

 

You run a gain stage to boost the voltage through rheostat. Then the comparator will have enough to do the job.

 

Probably going to use an LM324 to do all of the work.

 

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!

 

A simple low pass filter for the gain stage will cancel noise out.

 

Next up is to get one of the dimmer rheostats and find out what the actual resistance is across the total range.

 

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.