Captain Obvious

Glad to help. And of course, but some of the potential culprits may depend on the year you're working on. For example, (quick look at some of the wiring diagrams indicate that) 75 and 76 have a connector (C-2) between the fuse and the multifunction switch, while 77 and 78 do not. So if you're working on a 75 or 76, that connector may be corroded as well. But basically... Yeah. I would first start by putting a meter on both sides of the fuse and see what happens when you turn the switch on. Both sides should be solid battery voltage regardless of the switch position. And then work your way downstream from there if the problem isn't the fuse itself. Also, I'm assuming the fusible link and wiring to the "high side" of all the fuses is good or you would have mentioned a whole host of other electrical issues. I'm assuming this problem is relatively isolated to the lights. I mean, if you had a problem with the fusible link, it would show up in a whoooooole bunch of other areas as well. If everything else pretty much works, you ought to be able to start at the fuse box and work your way down from there.

Excellent. Not that it really matters, but I'm unclear on what Jeff meant by "it was the wires in the distributor", but like I said, doesn't really matter. I'm just glad you're fixed. And looking forward.... I'm gonna be no help whatsoever on any paint questions. Man's got to know his limitations.

First of all, I got no problem whatsoever with this: License plate bulbs (two), the remaining marker light, bunch of dash lights, glove box, cigarette lighter, ash tray.... Probably others. All in parallel? I got no problem with a couple Ohms to ground on the G/W. As for the readings you're seeing on the switch... I'm thinking you've got a high impedance connection somewhere upstream in that G/L wire. When the switch is in the OFF position and there is nothing connected to drag the G/L wire down, it floats up to battery voltage and looks good. But as soon as you turn the switch on, all those filaments in parallel will drag that high impedance source to ground. I'm guaranteeing that there IS current flowing. Just not enough for your home wiring style clamp-on meter to detect. So I'm thinking that's the issue. Finding it is a different story. Fuse that looks good, but isn't really? Barely holding on by a tiny sliver of metal inside? End caps that have been overheated and mostly de-soldered themselves? Corrosion on the fuse clips? Corrosion in the headlight switch? (Unlikely because you would have probably seen that while you were messing with the switch). Solder joint on the back of the switch that looks good, but really isn't. (I've never seen you solder. LOL) Anyway, happy hunting.

Glad you got it sorted! Enjoy the ride!

The only function of that arm on the front is for anchoring one end of the return spring? Seems like they could have put that somewhere else. Is there a center support tower? If there is, maybe on the rear side of that? Maybe at the back between the rearmost tower and the flange for connecting to the shepherd's hook? Does that use a custom adjustable length shepherd's hook?

Sure do! And I apologize they are still sitting there like that!!

Thanks. I was thinking about doing just that (after I saw your post on your 510 thread). "Test" out the amount of drop before I permanently committed to it. But I still need a pair of struts!

What do you mean when you say the pendulum slowly stops? Does the clock seem to work fine for a couple seconds in the normal position, but then over time the pendulum seems to lose amplitude and eventually comes to a stop? Pendulum won't start by itself, but seems to work OK for a little while if you give it a kick-start? I've seen that before. Any chance you can post a video? I'm with Dave... I suspect some long term drift of electrical components.

I'm not exactly sure what you're thinking is deformed, but if it's the bent looking "teeth" on the white pendulum gear, then there's no problem with that. They are supposed to look like that. That's what changes the "back-and-forth" motion of the pendulum into a unidirectional rotation of the next gear in the gear-train (the pink-ish colored gear). In other words, the pendulum gear changes direction as it swings back and forth, but the next gear in the system always rotates in the same direction. Those bent looking teeth are the clutch that allows that to happen.

Thanks for checking! And even if you do find the mate for the 240 version, that won't work for me. They need to be 260 or later. Here's to hoping I can turn something up. Kicking myself for not grabbing a set before the pandemic started. I had a couple options for a pair for under a hundred bucks and didn't get to it.

I suspect it's just designed too close to the hairy edge of working (or not working). The one or two prototypes probably worked great on the bench, but now that there are more of them out in the field, the parts tolerances variability and operating environment are having unforeseen results. Not that I've ever had that happen to me or anything........

That would be great. Let me know what you find!

Got it!

@Patcon, if you have a pair, that would be fantastic. I was hoping for a complete pair (with springs) so I wouldn't have to transfer everything over from the pair currently on the car. Best thing would be something with springs and hubs. I guess I don't care about rotors unless you've got something in really good shape. I was expecting to replace the rotors and strut inserts. I've got some feelers out for a pair. I've sent a couple messages to FB marketplace sellers and have gotten just one response from any of them. I'm not a FB guy at all, and I'm assuming I'm doing something wrong. I've also got a possibility on a pair from a guy here on the forum who will be getting a parts car soon. But at this point, it sounds like this project needs to pick up a little speed.

I don't have one of those clocks and have never seen the insides of one before your pics. So my only source of info is your pictures. That said... The resistor is a 200 Ohm, 1 Watt resistor. And the diode is a Zener diode, which is a little special compared to a normal diode. The important parameter of the diode would be it's "Zener voltage", and I cannot tell what that voltage is simply from the pictures. However, from the way it's used in the circuit, I would expect that it's zener voltage is between 5 Volts and 8 Volts. I doubt there is anything wrong with either of those components, but if you really really want to know more about the Zener, I can talk you through how to measure the voltage in question. And from what I've seen, you do a great job. Sometimes, you will go too far over your skis. Hopefully it's recoverable.

So it sounds to me like the answer to the question is "Use the coldest plug you can that stays clean." Would that be accurate?

Embarrassingly... No. I have spring perches which have been removed from a pair of scrap front strut tubes, but I never procured a set of front struts on which to transplant the donor perches. I'm not confident in the success of this project to just go ahead and modify the struts that are currently on my car. I want another spare set to cut up. In any event, here's where I am now: I have recently started a couple different avenues to get my hands on a pair of front struts to finish this project, but haven't had anything delivered yet. And no... I didn't start trying again because you prompted me. I really did start a couple weeks ago. So, is anyone parting out a 260 or 280 that has a pair of front struts available?

That capacitor is just used as a filter for a local derived power supply to drive the clock. The diode and resistor are a simple voltage regulator to knock the battery voltage down to a lower level. And the cap is there to make sure the clock circuitry has a nice clean voltage from which to operate. It would be very unlikely for it to affect the operation of the clock, especially on the bench. Enjoy the extra horsepower. Haha! You talk like you don't know what you're doing most of the time, but I think, in reality you got skills. Well done!

Haha!! Very nice! I'm glad the solution was a simple bulb change.

Oh. Well that's too bad. That would have been easier to deal with. So we're back to needing a different thermistor, or a workaround for the current one. My read on the thermistor is that (within reason), the cold resistance doesn't really matter. As long as it's on the order of KOhm(s), it should be fine. And as for the hot resistance, as long as it's on the order of a couple Ohms, it should be fine too. But the absolute numbers have wiggle room. What's really important is that it's small enough that it'll heat up when you push current through it, but not so small that it'll get so hot that it can't be cooled by a gas bath. In other words, what's most important is it's ability to generate and reject internally generated heat. If it's huge and has big winged heat sinks on it that do a fantastic job of getting heat out of it's core, it'll never heat up enough to get into thermal runaway. Conversely, if the core is surrounded by an insulating layer, you won't be able to get the heat out of the center fast enough and once it's in thermal runaway, you won't be able to recover. This sounds, at first glance, what is happening here.

Yup. Most of them should all be the same. The glove box might be the easiest to get to if you just want to pull a bulb. That or maybe the ashtray bulb? Thought of something though... After all the years and PO's though, you should make sure you've got the right bulb. Original is Toshiba A12V3.4. There are other numbers that have been used over the years as replacements, but if you find that Toshiba bulb, you know you've got an original.

Got it. Dr. Dave, Did you drill out the holes in the ZCD version yet to see if getting more flow in there helps? I'm still not yet convinced this is a completely electrical issue. If you're reluctant to make modifications to a unit that you still might want to return, you could possibly simulate larger holes by encouraging flow? Read... "Wave it around in a cup of liquid (to try to force fluid through the little holes) while monitoring the state of the lamp."

So basically your summary is that the Toyota thermistor works great, but the ZCD part does not. And not only that, but the Toyota thermistor seems to work great* with two wildly different bulbs. Did I get that right? * Assuming you don't leave it on so long that you fry your 6V bulb by applying 12V to it.

OP. Glad you're making progress and got it running!

Agreed. They did a pretty good job of making sure stuff could only go together one way, but maybe they missed this one. I don't have the spare parts laying around to check for keys, but looking at the pics, I don't see anything. I had my FI harness out of the car a couple years ago to replace a bunch of the connectors etc, and I don't remember any issues getting that FI relay back in correctly. I suspect that after fifty years, my connectors just kinda fell where they belonged. Either that, or as you mentioned, I just checked where the populated contact positions were.