SteveJ

I think this link will add to the discussion: http://www.atomic4.com/dwell.htm The title is What is Dwell Management and Current Limiting?

Well, I got my old wire tracker out. At first it didn't want to behave, but soon I was getting a good tone from the end of the wire to the gauge.

I have the HF unit, and I actually used it at work...about 14 years ago. That was for wiring in a bunch of metal boxes, and I didn't get a bunch of false readings. After a while, I got to where I didn't need it any more. Does it look like your harness has been altered/modified? I might have to dig my tracer out and play with it again.

You may have misunderstood. It could be at the bullet connector. You might not be able to see it, especially if it's corrosion. Also, there could be corrosion at the connector between with engine harness and dash harness.

Yep, I was talking with @Captain Obvious, and he pointed out the tachometers were different. Apparently someone converted a 260Z/280Z tach to fit into a 240Z. The wing nuts were added to the tachometer

My friend, Google, found a link that led me to this: http://www.mgb-stuff.org.uk/tachtest.htm

It would be highly unusual for a wire to break in a wiring harness unless the harness was pinched hard or pierced. The usual suspects would be where the connectors are attached to the wire. That would be fatigue breaking the strands or corrosion. However, if you wanted to look for a break in the wire, you would need something like this: https://www.amazon.com/Electrical-Wire-Tracer-Continuity-Automotive/dp/B08L6NYQYK You would detach the C1 connector and clip the red lead to the yellow wire. Then clip the black lead to ground. You would use the probe to "sniff" the wire through the harness, and if you lose signal, that would indicate a break. The bottom line is that you should inspect the connectors carefully at both ends (C1 and at the sensor).

Me! Me! Me! I want to get geeky! I even started playing with the inductive pickup I bought for my scope. I really need to re-familiarize myself with working with o-scopes. It was a LONG time since collage.

I should add that for top dollar, get photos underneath the car and all over the engine bay. Also take close up photos of the rust prone areas.

If you have Hagerty, you can use their pricing guide. I used to think it was high, but the market caught up for the most part.

You ought to invite me up there sometime.

Here is one thread I found: Some internal photos in this thread:

Yeah, I put some more on order from Amazon after I confirmed the fit. Looking into it more, I looked on Rockauto for the fitment of the S847 and looked at the socket part numbers for those cars. It looks like there are some alternative part numbers for the 1156 and 1157 style sockets.

Somewhat as a follow-up to my earlier thread: I purchased an SMP S847 socket. I tested it out in my 240Z, and it seems to fit just fine.

That's the thing. Any of us (and that includes me) can make those little mistakes, often times not even realizing it happened. I've done things like try to start the car without the wire on the coil or with the rotor sitting on the fender. When it's not as obvious, it's easy to get frustrated and start loading the parts cannon to replace all of those bad parts that aren't really bad. In my friend's case, I could hear his frustration as he repeatedly swapped in parts with no success. That's why I went over to his place with the plan of getting a baseline and examining each part and correct each issue I encountered. This time, it was an easy solution.

I don't think it has changed since a year ago.

A friend installed a Pertronix Ignitor I into his 240Z, and he contacted me for help since he could cruise fine at low RPM, but whenever he tried to get on the gas, it would stumble and cough. He thought it might be a coil impedance issue so he tried various coils but kept having the same issue (and sometimes even worse performance). Since he has been wrenching on Z cars since the mid 80s, I figured he had gone down the wrong rabbit hole at some point. I loaded up the rescue wagon and headed over to his place. The first thing I did was connect an oscilloscope to see if I could pick up an obvious miss. The scope left me with the impression that something wasn't happening right as higher RPMs. (I might recreate his problem on my 240Z and see if the scope shows the same thing. If it does, I'll make a video to help people with diagnostics.) I looked at the resistance to chassis ground at the distributor. The resistance was nearly zero, so it wasn't a grounding problem. From some old threads here, I thought the vacuum advance might be an issue. Unfortunately his hand pump would let me pump up enough vacuum to check, so that was tabled. Next was inspecting the distributor cap. The contacts were clean as was the rotor. So I moved to inspecting the posts where the wires land. The wire on the center post wasn't seated far enough down, so I pushed that in. Then I pulled off each wire one by one, starting with #3 and working clockwise. It was good, #5 was good, #1 was good, #4 was good, but #2 was not. The boot was almost off the wire. There was no way it was getting a good spark. I positioned the wire properly in the boot and re-seated it. Then I checked #6. It was good. I looked at the scope again. It looked better, but I didn't shoot video. After my friend fixed a fuel leak at the banjo fitting on the rear carb, (The fitting wouldn't seal, so he replaced it.) he took it for a spin. He said there was no hesitation, and it pulled hard past 5,500 RPM. The moral of the story is that when you can't figure out what's wrong, step back and go over everything from the beginning. Sometimes you have to eliminate each and every variable until you have the solution. I love getting another Z back on the road.

The voltage regulator is the part on the right. See the red arrow. If it's working properly, you should see it opening and closing rapidly, like you saw the ammeter needle moving in my video. As far as fix it, you would have to re-wind the coil with that fine insulated wire.

Reach out to Alan Poindexter at https://vintagezparts.com/ He focuses a lot on Z31s.

There are places that might be able to repair/replace the voltage regulator. https://www.google.com/search?q=automotive+gauge+restoration&sxsrf=ALiCzsa7dCxxAJmczzDprB3YHBA44vbQSw%3A1663426703398&ei=j-AlY7jrF7-kqtsPhJys0Ag&oq=automotive+gauge+res&gs_lcp=Cgdnd3Mtd2l6EAEYADIFCAAQgAQyBggAEB4QFjIGCAAQHhAWMgYIABAeEBYyBggAEB4QFjIGCAAQHhAWMgYIABAeEBYyBQgAEIYDMgUIABCGAzIFCAAQhgM6DQgAEEcQ1gQQsAMQyQM6CggAEEcQ1gQQsAM6BAgAEEM6CAgAEIAEEMkDSgQIQRgASgQIRhgAUPoJWL8MYNUcaAJwAXgBgAHlAYgB0gOSAQUwLjIuMZgBAKABAcgBCMABAQ&sclient=gws-wiz ebay offerings are probably cheaper. https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2380057.m570.l1313&_nkw=280Z+temperature+gauge&_sacat=0 If you go the latter route, save your gauge. Someone may want it to have one to restore later.

In my never ending quest to find parts that no one seems to be looking for, I finally found what seems to be a good replacement for the single filament (1156 style) bulb sockets for the tail lights and reverse lights. The Dorman 84808 fits snugly in the tail light housing. You can find them on Amazon and Rockauto. I'm going to get a Dorman S847 to see if it's a suitable replacement for the 1157 sockets.

Probably. I'm starting to see a pattern.

Yes, I am.

No fuss, no muss, no unsightly build-up. We are glad your Z is operating normally. I would not be surprised if it drove better now.

FB is good for posting pictures and getting lots of bad advice that buries the responses from the few knowledgeable people.