Earlier this morning I said these fail. Actually the same thing normally fails in every one of them. Let's see how to fix it, since this switch will be infinitely better than the imported ones. 1. An overview of your switch. This is one I removed from a truck about 40 years ago and never used because it doesn't work. (first image below) 2. Press the release button on the bottom and remove the knob rod. You may have to wiggle the knob back and forth to make this happen. (no image) 3. Using a screwdriver, carefully bend up the tabs on one side only. (second image below) 4. Remove the top and contactor and the fiberglass plate below the contactor. (third image below) 5. The top of the contactor and the three bumps. (fourth image below) 6. Remove the insides (except the sliding detent rod...leave it in place as shown). Discard all the broken bakelite bits. (fifth image below)
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Now that you've cleaned the old junk out, get some common chassis grease or cornhead grease and:
7. Begin reassembling, greasing the sliding detent rod. (image one below) 8. Be certain to grease the bottom and sliding sides of the bakelite piece. (image two below) 9. Install the bakelite piece over the sliding detent rod and then angle the greased rod clip in as shown. (image three below) 10. Install the three small springs. (image four below) 11. Set the contactor and fiberglass plate below it in place. (image five below)
Carefully set the top plate on, sliding it into the two tabs you did not bend upward. Turn switch up so you can check to be certain the contactor is still positioned correctly. (image one below) Press top plate down and hold in place. (image two below) Using water pump pliers, carefully bend back the two tabs you bent outward to release the top. (image three below) Now connect the power supply for the dash lights. (image four below) And now you're finished and your switch should work well for a long time.
Okay, what happened to cause your switch to fail? Generally the end of the sliding bakelite piece breaks off, these pieces fall down and prevent the slider from working at all. Take a look at image five below. This is where all the plastic bits and pieces you cleaned out earlier originated. Good luck.
One further image. Please look at what you may see when you first remove the top plate. The broken bakelite pieces (broken by the knob rod pushing into them) have fallen off behind the slider and will make movement of it both erratic and finally impossible. You can see where the knob rod would strike the back side of the bakelite slider in this image. The switch (aside from this) is otherwise a very simple design.
Never say never, but I've never seen any parts available, Rusty. You know for years these sold new for $6 or $7, and I'm sure very few people ever took one apart to rebuild it. In fact, it was widely known you could buy a brand new one from Western Auto for $4, remove the "universal" knob/rod and slip your AD knob/rod straight in there. It was the same switch, made by Delco and sold as a universal model. The only trick was you had to file a new notch for it as the lock tab was 45 degrees different. My truck has both of these notches and it originally came from California, so I'm certain some parts place out there sold the same switch. But things have changed.
From what I've seen only one part really wears out so to speak. That is the bakelite sliding block. The slot holding the knob/rod keeper wears and this lets the knob rod slide ever so further in. All it takes is one hard push of the headlight knob inward (which happens when the bakelite slider and the sliding detent pin lose lubricant) and pow...the back is knocked out. Once that happens, the switch is on borrowed time. I suppose you could rebuild the top piece with small brass screws (to replace the pins and rivets) if need be, but I've never seen one wear so far that these quit working. This switch had seen a decent amount of use when I got it, and you can see the contacts on the top plate are nowhere needing attention:
Thanks! Hope it helps. Sounds like this will fix your situation. Actually I have another of these I'll be repairing soon. Same problem...won't push in all the way and the image up there shows why. Good luck.
I mentioned I had another switch needing attention and I have some nice blank formatted diskettes, a cup of tea and 30 minutes to kill. This switch was sold originally by NAPA (I bought it maybe 30 or so years ago) and like the ones sold by Western Auto was made either by Delco or the subcontractor who made it for Delco. Same exact switch made using the same dies, etc. But this one wasn't acting the same way. It: 1. no longer was smooth to use 2. turned the lights on but rather erratically 3. didn't dim dash lights anymore.
So, let's look inside. I'm pretty certain we're going to find something different and have some new problems to fix, but the broken bakelite may also be a problem. First, a look at the switch...image 1 below Second, I bend carefully back two tabs on one side only...image 2 below Third, I lift off the top and slide it out from the tabs I did not bend back and...Aha! The problem you can clearly see in image 3 below. At least one of the problems. As you can see, the contacts are worn and ugly looking and there's generous evidence of dust, dirt, etc. Not pretty but not a death sentence by any measure. Four, we see the contactor is the same exact design...image four. and Five, you can see I've spent a few minutes with a small piece of wood and some 100 grit sandpaper wrapped around it to level the contact plate and contacts back to a like-new condition. I'll go over them with 320 sandpaper and then 600 grit sandpaper to make them nice and smooth. These guys aren't going to give us any trouble for a while now.