Captain Obvious

Well we could work into this in a couple of ways. First option would be to start by shotgun replacing the electrolytic caps (as DaveWM mentioned) and see what happens. Electrolytic caps are known to not last forever. They contain chemicals inside that eventually dry out, or leak out, or sometimes they fail short. In any event, they're a known source of long term issues and may or may not be what's causing the problem with your clock. So I'm certainly not poo-pooing the shotgun approach in this case, it's a valid approach. If that shotgun approach isn't doing it for you, we can get into some specific measurements you can take that might help narrow down the problem. And speaking of which....... When you say you have continuity across the circuit, where are you taking that measurement? If you're taking that measurement across the blue and black wires, then there's a problem. You should not be seeing significant "continuity" across those two wires. So talk some more about that.

I've been inside that clock version in the past (surprised? ). Not an expert, but might be able to help. What's yours doing or not doing? Completely stone dead?

And about your fuel lamp, yes... In 75 that lamp was located in the small square location below the radio. In later years, they moved it up to above the center vent outlets in the HVAC panel, but your car (especially since it's a California spec) has those locations above the HVAC populated with other items. And honestly, it probably doesn't work anymore. Your thermistor in your gas tank probably burned open years ago.

Best way I could describe the connector mating: 1) Hold your two hands out in front of you, palms facing up. 2) Then bring your two palms together. That's how the connectors on the wiring diagrams mate. And as for which side is which... In general, things are laid out on the wiring diagrams like they are laid out in the car. So for the Cn connectors the half on the left is the engine bay side, and the half on the right is the passenger compartment side. Does any of that help at all? As an additional aid on this C-2, the "X" is an unused cavity in the connector shell. That should help show how the two sides go together "mirror like". For example, the G/L on the far left connects to the G/L on the far right. While the "X" on the left connects to the "X" on the right side.

Actually, taking a closer look at your pics, it looks like the white two position connector includes a red/GREEN, not red/blue. And if that's the case, then the wiring diagram indicates it was for the fog lamp switch. Optional for other countries, I think.

Yup, that color pair of red/blue and green/white are used pretty much universally throughout the dash and console as illumination lamp power. The red/blue becomes hot when the headlight switch is turned to the first position, and the green/white is pulled to ground through the brightness control knob pot. The wires you found there could be for the A/T gear lever position illumination and/or for the ash try illumination bulb. Don't remember offhand if they had that yet in 75. In any event, they are dash/console illumination.

If everything else is accounted for, then I would also assume that 6-position connector is for the radio. There are five wires leading to the original radio: The red/blue and green/white are for the illumination lamp inside the radio. The white and white/black go to the speaker, and The blue wire is hot when in ACC and ON. Note that power wire goes dead during cranking, so when your voltmeter shuts off while you are running the starter, that's why. Also note that same blue wire also supplies power to the rear defogger switch and the antenna switch. So you could verify you've got the right connection by confirming that it's tied to those other two items. And....... One last thing to talk about. You mentioned earlier about a wide band? That meter system may draw significant power (because of the sensor heater?) and you might not want to pull power for that meter off the same place you put your voltmeter unless you are sure you've got a rock solid clean connection all the way back to the source. I'm thinking the current draw for the sensor may affect the voltage reading. Your voltmeter draw will be negligible, but your wide band may not be.

Oh... And maybe slow down a little. Focus on one thing at a time. Pick one problem and get that item working and then move on to the next one. It's easy to become overwhelmed and then overwhelm your help.

Here's a sketch I whipped up a while ago showing the functions of the ignition relay. Might help augment what SteveJ already posted.

If I'm understanding correctly, you want to put a voltmeter in the console, and you want a switched voltage signal to connect it to? If that's the case, then you could just tie into the blue wire that powers the radio. It's switched, and it's already in the console harness. If all your connectors are clean, it "should" give you an accurate reading of system voltage. Oh, and BTW, the color wiring diagram you posted above is for the 77. Many (most) systems of the 77 are very similar to the 75, but there may be some differences. I normally would start by looking at that 77 color diagram, but to be sure, you should also double check the old style 75 diagram out of the FSM. Especially wire colors, etc.

Thanks Steve mudkip777, Basically, the process goes like this... Put the carbs together and put them on the car. Everything connected per normal. Then pull the black rubber tube off the nipple on the bottom of the float bowl and temporarily connect up a length of clear plastic tubing in it's place. Position the clear tube like the pics in that thread and then run the fuel pump. In your case, that probably means cranking the engine to make the mechanical pump deliver fuel. The fuel level the develops in the bowl (and hence the clear tube) should meet the spec in the service manual. I would suggest pulling the plugs and make sure you have a fully charged battery. It could take some cranking to get fuel to the bowls. That's the clear tube method in a nutshell. Details left to the studied reader. Here's a couple related pics that might help Separated from the rest of the carb, but here's a 240 bowl: And here's a different carb, but the concept is the same:

There are some pics on the site that show how to check the float bowl level using a clear piece or plastic tubing. I'll dig around a little and see if I can find them, but someone else will probably find them faster.

Oh, OK. I saw the note about struggling above 4K and I was attributing that to other stuff that would be dealt with later. So it sounds like you might have multiple things going on. Let's back up a little... Have you run a float level test using a clear tube to verify that the bowl levels are correct? If not, I would start there.

I'm not really concerned by the compression test results. They're all consistent, but a little low. Sounds to me like it's an old Z engine in typical condition. No problem. As for your carb issues... It's all in the adjustment of the carbs. The front carb has no vacuum at idle because it's all the way closed shut. And when it's all the way closed, it doesn't contribute anything to the running of the engine. You're idling completely on the rear carb. Once you get off idle and the linkage opens the front carb, it runs off both carbs and you're OK. But at idle, the front carb butterfly is adjusted completely shut and that carb isn't doing anything. Bottom line? Close the rear carb some and open the front. Adjust them so both carbs are doing something, even at idle.

If you had one carb completely off, all six cylinders had a pretty clear path direct to atmosphere. Three of them (obviously) direct, and the other three almost as good to atmosphere through the balance tube. Point is... I don't think you have to run the test again simply with the throttle held open. I think your previous test already took care of that.

Sending you a PM about the tach. ☺️

Haha!!

"Acid solution containing Hydrofluoric acid, Sulfuric acid, and Nonylphenoxy Ethoxy Ethanol Have a 0.13% solution of zepharin chloride solution on hand" Yikes. For those who don't know anything about hydrofluoric... If I remember correctly, the zepharin chloride is an emergency measure to give it a calcium target that it likes better than the calcium in your body. Like your bones. Classic tradeoff between safety and effectiveness. That stuff probably works great.

Roger that. Figured there was an easy answer. This issue is fresh in my mind as I've been helping a local guy with his Z and that was one of the issues with his motor. He was running uber-lean for many reasons, and one of them was a mismatch between gasket design and fuel delivery design. He didn't do it, but his motor came to him with the wrong gasket style. Here's a pic looking into the intake manifold while holding the gasket in place. The gasket pretty much blocks off the injector holes completely. His injectors were spraying into a closed door:

Pic shows an intake/exhaust gasket for carbureted applications which blocks off the fuel injector holes. Are you switching to carbs? Or is just a mechanical mock-up? I'm sure there's a simple answer, but I just have to ask.

I will take a look to see if I have one of those switches. If not, I'm assuming the aftermarket add-on you have installed (functionally) does the same thing? What the stock switch does is connects the blue/white to ground any time the switch is in any position other than OFF. Your switch may not do the exact same thing electrically, but functionally within the system, it should serve the same function (to turn the compressor off unless the fan is spinning).

And I had the pleasure of spending significant time with you at both. Here's to hoping we can do that again at a future event!

Thinking about it for another second though, there is one detail that bears mention... The "Fan is not in the OFF position" signal is built into the four speed switch that came with the A/C cars. Since your car did not come with A/C and has the three speed switch, you need that auxiliary aftermarket installed switch. Here's a couple pics of the four speed switch:

Yes, the resistor is different. You see..... The non-A/C cars (like yours) have three fan speeds while the A/C equipped cars came with FOUR fan speeds: But the top speed bypasses the resistor in both cases so the highest speed is the same. Point is... Yes, the resistors are different, but really doesn't matter for what you're doing.

I assume the switch responding to the fan position disables the A/C it the fan is in the off position (so you don't slug the compressor). And the other switch probably cycles the compressor based on the temp of the air through the evaporator. I'm pretty sure you knew all that already, so I guess I'm not sure what the question was?