The Stovebolt Site Forums The Shop Area The Electrical Bay Repair your headlight switch...tutorial

It should be ok. Here is the caveat, however (and the reason I'm still writing about this is I don't want there to be a single surprise discovered by anyone out there): if all is well and the dash lights are the solitary draw on it, everything swims along nicely. If for any reason something happens to ground one of those dash light wires (a wire break, somebody crudely added an uninsulated connection when they wanted to add a light wire for their tachometer, vacuum gauge, radio, etc), then the coil will heat to a glowing red tout de suite. It looks just like a miniature hot plate. A lot of amperage flows through the headlight switch and this resistance wire takes just a blink of time to glow in the case of a short. Yes...there is a circuit breaker, but there are 3 things about that: the coil might glow before that breaker activates, one never knows if the breaker is working correctly until it is needed and the breaker re-sets itself so the coil will keep glowing/not glowing as long as the short is there. While working on the fuel sender project, I became curious about how little voltage & amperage would be needed to make resistance wire glow...for anyone who doesn't know, this wire is used to make smokeless tobacco units. Turns out a common AA battery will make a 6 inch piece of wire hot enough to blister your fingers. That battery is 1.5v and milliamps of power. I hooked that same piece of wire to a 12v power supply I use (12v dc with 1 amp of power) and with a direct short circuit, the wire turned cherry red in about 1 second.

Going to try one more trick to see if it will solve the problem the wiper looks like it catches on the spring so I am going to try and clean up the wiper so there is no edge for it to catch the spring .It also looks like there may be a small bump on the porcelain that holds the end of the spring in the porcelain at the end were it is not attached to the rivet

Jon, thanks for the lesson on resistance wire. I really appreciate the time you invest in SB. Your knowledge is a tremendous asset to all Stovebolters.

Kevin, let us know how your dimmer repair turns out. Feel free to post some before and after pics too!

Will let everyone know the results ,here is what the start looks like.all looks good until the switch is turned then this happens pictures .

That coil appears to be disconnected, Kevinski. From your images it seems to be broken. I'll be interested to see what you find.

I will have to look again on my other switch but I thought the coil was only connected on the one end ,it also looks that way on the pictures from Kevin from Alaska.It looks like there should be a bump in the porcelain to hold the spring in its centre and there is no wire on the rivet were the end of the spring is not connected .

Okay checked out the other switch and it looks like the spring has no connection on the one end ,the porcelain does have a finger that goes into the centre of the spring to hold it and that is what broke on this one to cause the spring to go like a slinky when you turn the dimmer switch .I cleaned up the porcelain pulled the spring out and straightened the loops as best I could ,put in some j b weld at the bottom and will looks like it will do the trick as long as the j b weld holds up .The picture with the red on it is from another switch that is good

So, the porcelain has a keeper at each end of the resistance wire to hold it in place? Are there contacts behind the resistance wire? I'm trying to understand the current flow through the dimmer component, thanks.

I haven’t tested the switch but out of the 3 I have they all look the same on the one end the spring is attached to the rivet on the other it is held in by what looks like a bump in the porcelain that goes into the centre of the spring .I am not electrically inclined but I think the current would go through the spoon that turns and rubs on the spring as it is insulated from the housing .Maybe Jon G can help on this one .

I don't have mine in front of me, but the end of the spring that's attached to the rivet is one part of the circuit, and the wiper that runs along the spring is the other part of the circuit. The difference in the length of the spring between the wiper and the riveted end changes the resistance of the circuit and the brightness of the dash lights.

Thank you both very much!

Thanks Jon G for the information, my problem is the Bakelite material is broken in pieces and the parking light leg has come off

One point to add to the discussion, my dimmer quit working - I just connected dash lights to the tail lights terminal. They don't dim but they work.

I'm looking into the possibility of making new bakelite pieces, but so far I haven't been able to find any affordable options. I'm not married to the bakelite concept, either. I'm also considering making a mold and using fiberglass. We'll see. Fiberglass (for anyone who has bought any lately) has suffered the same inflation problems our entire economy has since January.

Have you thought about using this?
phenolic resin

Dimmer switches are readily available from most local parts houses as well as the Chevy parts places that sell restoration parts.
Harold

Thanks, Wayne...I use phenolic sheets to make circuit boards, but for this I need something that can be either melted and poured into a mold or mixed and poured into a mold. In a perfect world, it would have a little "give" so that it wouldn't break so easily (bakelite is very brittle), but that may be asking too much since I don't have injection molding ability. I'll see. It is possible phenolic sheets could be used with some machining work. Epoxy is about $25 a pound and fiberglass resin is about $70 per gallon...pricey stuff.

Look for someone who does 3-D printing. It would probably be a snap to reproduce, as long as you have all the pieces of bakelite that you can reassemble for use as a pattern.
A friend of my son-in-law has a small 3-D printer that work. I'm thinking about asking him to do a heater knob for me.

I had that same thought, but the one friend I have who understood those printers retired and no longer has access to the one he used at work. I have one that has almost all the pieces. The problem is I haven't found an original switch yet with no broken bits, so I expect I'd have to cheat a bit. Given what I've seen I think these may have started breaking pretty soon in their life...possibly within a couple of years. I do know where some might be and I need to drive out to see the owner of them...

Really appreciate the cool explanation on a rebuild of that there switch. Quite detailed and to the point Thank you..

Thank you much for the compliment. Very nice to see folks are using the tutorial. There have been others and there will be more...you just have to search for them.