SteveJ

NO! Go back to my post. Read it. It has diagnostics. Isolate. Measure. Inspect. Most of all be patient. It takes time to type up a good diagnostic.

There are parallel paths for current. IT=I1+I2+I3 When C3 was disconnected, one path was removed. When the dimmer was cranked up or removed, one path was removed. All paths together make enough current to blow the fuse. Easy way to diagnose: Use a clamp ammeter (https://www.amazon.com/gp/product/B009CNYJG2) to measure the current on each branch (front, dash, rear) while they are isolated from the others. While noting what lights are on, you can estimate the current. The bulb wattage is in the FSM. You probably have one or more exterior sockets with corrosion. That can increase the current draw. Before you do the testing, you might want to fix the wiring harness at the headlight switch. Vintage connections (http://www.vintageconnections.com) has a perfect replacement 9 pin connector. Been there done that. Unfortunately that site is down right now. I'll do a follow-up post on how the break down the circuit for testing.

Can you answer that, @esprist?

Hatch strut - http://jdm-car-parts.com/products/rear-hatch-shock-for-datsun-240z-260z-280z The pulls for the door locks may still be available from Nissan. I'm not sure if these would work on your heater controls: https://zcardepot.com/interior/dashboard-parts/heater-control-knob-set-knobs-3-oem.html?search=heater&page=2

The fusible links. For the factory testing methods, I would have to read them. It's been a while.

Physically remove the link and test it for continuity. They can blow internally and still look intact.

By the way, how does the curb weight of the 240K compare to the 240Z?

That looks a lot better. Are you going to flush the cooling system to make sure there isn't gunk left over in the block?

I was also impressed with the service I received when my Z broke down. The operator was very professional and efficient. Within about 45 minutes from me placing the first call to them, my car was loaded on a flatbed. They also offer assistance with parts tracking for restorations, though I haven't tried using that service, yet.

First, I'm glad you're using a meter to diagnose the problem. You'd be amazed at the number of people who try to diagnose electrical problems without one. (Kind of like balancing the carburetors without a flowmeter.) After following Cliff's suggestion to adjust the belt, download a copy of the FSM. The link is in my signature. Look at the EE section, and follow Nissan's procedure for testing. Let us know what the results are.

Like I said before, I could make it up to see you if you need some help.

That's why for my Z I run GoPro clones facing front and rear.

To ensure you have good voltage, I suggest hooking up a battery charger to the battery and set the charger to the lowest setting. Please record your steps and your meter readings. It's tedious, but it helps with diagnostics when I can't see what you're doing. First, remove the relay from the wiring harness. 1. With the headlight switch on, at the plug for the relay, check voltage from the RB wire to ground. You should see 12 VDC (or whatever your battery voltage is). Also measure voltage from the RW wire to ground. You should also see 12 VDC. If you have voltage on one wire and not the other, check continuity from the headlight plug to the relay socket on the wire without voltage. You might also use an ohmmeter to look for resistance across the headlight elements with an open line/infinite resistance indicating a bad element. 2. Pull the fuse for the right headlight. Recheck voltages. Put the fuse back and pull the left headlight fuse. Recheck voltages. Also while the fuse is out, check it for continuity, just to make sure the fuse is good. These circuits are designed to backfeed between left and right on a blown fuse. That can make diagnostics tricky. Once you have determined that the wiring is good up to the relay socket, you can turn off the headlight switch and jumper the RB wire to ground. Turn on the headlight switch. If you don't have low beams, pull the headlights and check for continuity between the pin for the RB wire and ground. Also check the voltage between the positive pin on the connector and the RB wire. Report the results. Repeat the process above with the RW wire. Remember that you have to pull all of the headlights when you want to run the meter checks. If we can't figure it out the go-around, heck, I might just drive up there in a couple of weeks.

Hang in there.

I'm glad to hear your injuries weren't more severe. Let us know how things work out for you.

Give me until sometime on Sunday to write up some advanced diagnostics for you.

Don't forget about the antenna drain grommet, too.

I also sent you a text.

I can try to break down the circuit for you. The green/blue wire comes into the headlight switch. When the switch is in the #2 position, you should have 12VDC on the red/yellow wire coming out of the switch. That wire goes to the fuse box where it connects to the left and right headlight fuses. The left headlight fuse comes out to a red/blue wire. The right headlight fuse comes out to a red wire. They go out to their respective headlights. The red/black wire is for the low beams and goes back to the headlight relay. The red/white wire is for the high beam, and it also goes back to the headlight relay. The positive for the coil voltage is green/blue. The negative for the coil voltage is black/red. The black/red wire goes to the turn signal switch where is open or connected to ground, depending upon the switch position. When the coil is de-energized, the red/black wire is grounded, finishing the circuit for the low beams. When the coil is energized, the contacts connect the red/white wire to ground. So, if the headlight switch is on with the turn signal switch on low beam, how could you see 12 VDC on both sides of the high beams? If you don't have the ground at the relay, you only have potential voltage. The headlight elements acts as a piece of wire and not a load. That's why you see voltage on both sides. The voltmeter has significantly higher resistance compared to headlight element.

I ended up buying some wedge sockets and LED bulbs in the appropriate colors for their sockets. I replaced the existing sockets with the wedge sockets, removing the lenses. I used uninsulated butt splices covered in heat shrink tubing to splice the new sockets in. The gauges can be removed without pulling the dash. Get a copy of the factory service manual (FSM) for instructions. It worked for me.