SteveJ

The best way to reduce heat in the parking light and headlight circuits is to use LEDs. For the other circuits, look at the ones using 20A fuses. (76 fuse box as an example) If you keep the same placement, note how close those 3 are together.

So I'm guessing that is for a 280Z. I suggest you consider subjecting it to some thermal testing, considering that some of those circuits can pull some current, such as the parking lights and headlights. It's not fun to find that your fuse box has melted down. Been there, done that with the stock 240Z fuse box.

Gateway Classic Cars of Atlanta was holding its monthly Caffeine and Chrome meet today, and the Georgia Z Club was the featured club this month. While Gateway gives the featured clubs money based on the car count (up to $200), we decided to donate the money to Toys for Tots. With the great weather and spirit of showing up to get money for Toys for Tots, we had plenty of Z cars show up, with every generation represented. We don't get that too often.

Yes, the plan is to make a harness go to between the factory harness and the amplifier.

It doesn't have to be an improvement. It just has to work. I know of at least 3 Z cars in my area that are having problems because the amplifier failed. Since the original is NLA, if I can get this to work, people will have functional wipers. I have looked at other intermittent relays, but this will probably be the best way to work with existing wiring.

Can anybody guess what I'm about to try?

Thanks for the document. It's a good reference. Keep going with the updates!

Based on your photos, I concur with your assessment. With Relay A gone, you have no problem with the alternator upgrade.

Okay, your car probably has the fuel pump relay modification. It looks like you have two wires at the starter solenoid. There is no need to cut any wires! Just unplug Relay A. The relay is located on the passenger kick panel. If the relay is plugged in and you have that alternator mod, you will run your battery down.

Measure voltage to ground on the backside of the connector. One pin should have voltage with the engine off. That is the battery sense. Also, look to see if the connector is corroded.

But have you checked battery sense voltage at the alternator?

Yes. For the 78 it's easier than for earlier S30s since your car is already set up for an internally regulated alternator.

It has to be a 4 cylinder Frontier or Xterra to have the correct pulley.

I haven't had any issues with the Frontier alternator I bought from Rockauto. https://www.rockauto.com/en/moreinfo.php?pk=8829284&cc=1359200&pt=2412 Rockauto has several other brands listed as new (not reman). You also have to buy a plug like this to integrate it into the wiring. https://www.amazon.com/gp/product/B07ZMN2B59 Attach that plug to a 2 pin connector from Vintage Connections (http://www.vintageconnections.com/Products/Detail/79), and you can plug the new alternator into your car. Last, but not least, you'll need to replace the ring on the alternator charge wire with one that can go on the M8 post on the alternator.

There is only 1 bid on record for that username (for that "engine") and no comments on record. It can make a reasonable person wonder.

The main reason behind the recommendation for marine wire was they seemed to have every combo needed. I actually found a site last night that has GXL wire with tracers, but they don't have every color combo needed for the Z. Here's an updated list for wire colors: BR https://www.acdcwireandsupply.com/GXL_14_AWG_AUTOMOTIVE_WIRE_BLACK_W_RED_STRIPE_p/gxl-14awg-0103.htm BW https://www.sherco-auto.com/striped-tinned-tracer-primary-wire-14-ga-x-25-ft-black-wwhite-stripe-25-ft-usa-made-for-marine-and-automotive-use-also-in-25-ft-rolls.html BY https://www.acdcwireandsupply.com/GXL_14_AWG_AUTOMOTIVE_WIRE_STRIPE_p/gxl-14awg-0105.htm GB https://www.sherco-auto.com/striped-tinned-copper-tracer-primary-14-ga-x-25-ft-coil-green-wire-black-stripe-usa-made.html GL https://www.sherco-auto.com/primary-tracer-marine-tinned-copper-14-gauge-awg-x-25-ft-coil-green-wire-blue-striped-usa.html GR https://www.acdcwireandsupply.com/GXL_14_AWG_AUTOMOTIVE_WIRE_STRIPE_p/gxl-14awg-0403.htm LW https://www.acdcwireandsupply.com/GXL_14_AWG_AUTOMOTIVE_WIRE_STRIPE_p/gxl-14awg-0702.htm LY https://www.sherco-auto.com/striped-tinned-tracer-primary-14-ga-x-25-ft-coil-blue-wire-yellow-stripe-usa-made.html RB https://www.acdcwireandsupply.com/GXL_14_AWG_AUTOMOTIVE_WIRE_STRIPE_p/gxl-14awg-0301.htm RB https://www.acdcwireandsupply.com/GXL_14_AWG_AUTOMOTIVE_WIRE_STRIPE_p/gxl-14awg-0301.htm RL https://www.acdcwireandsupply.com/GXL_14_AWG_AUTOMOTIVE_WIRE_STRIPE_p/gxl-14awg-0307.htm RW https://www.acdcwireandsupply.com/GXL_14_AWG_AUTOMOTIVE_WIRE_STRIPE_p/gxl-14awg-0302.htm RY https://www.acdcwireandsupply.com/GXL_14_AWG_AUTOMOTIVE_WIRE_STRIPE_p/gxl-14awg-0305.htm YB https://www.acdcwireandsupply.com/GXL_14_AWG_AUTOMOTIVE_WIRE_STRIPE_p/gxl-14awg-0501.htm YG https://www.sherco-auto.com/striped-tinned-tracer-primary-14-ga-x-25-ft-coil-yellow-wire-green-stripe-usa-made.html YR https://www.acdcwireandsupply.com/GXL_14_AWG_AUTOMOTIVE_WIRE_STRIPE_p/gxl-14awg-0503.htm YW https://www.sherco-auto.com/primary-tracer-marine-tinned-copper-14-gauge-awg-x-25-ft-coil-yellow-wire-white-striped-usa.html B https://www.acdcwireandsupply.com/Gxl_Automotive_Wire_p/gxl-14g-01.htm G https://www.acdcwireandsupply.com/Gxl_Automotive_Wire_p/gxl-14g-04.htm L https://www.acdcwireandsupply.com/Gxl_Automotive_Wire_p/gxl-14g-07.htm R https://www.acdcwireandsupply.com/Gxl_Automotive_Wire_p/gxl-14g-03.htm

Now I have a few minutes for the long-form answer. For the 240Z, the ammeter measured the full current between the battery and the ammeter. If there was a short in that area, the full ammeter current would feed the fault. The battery was limited by the fusible link. (Don't be fooled, while the FSM wiring diagram shows a fusible link off the alternator, I've never seen a car equipped with one.) Also, if the ammeter failed, the car was dead. If it was running when the ammeter failed, it might keep running, but as soon as you turn it off, the car would not restart since the battery was now isolated from the majority of the electrical system. For the 260Z, the design was improved by using a shunt to limit the current flowing through the ammeter. Also the failure of the ammeter would not strand the car. Less of a fire hazard and eliminated a single point of failure. That's definitely an improvement. The 75 carried on this design, and the 76 introduced the voltmeter.

The shunt is for the Ammeter.

I've never had the opportunity to tear into the wiring of a 75, but I strongly suspect that the interlock relay has been completely disabled. Ford developed the seatbelt interlock relay and presented to the NHTSA in the early 70s. The bureaucrats thought that it was the perfect solution for getting people to wear their seatbelts, so they quickly added it to the regulations for the 74 MY cars. This meant all of the other automakers selling cars in the US had to come up with their own interlock schemes and QUICK. Many of the implementations left a lot to be desired. I remember my older brother figuring out how to disable it in our family's 74 Impala. Faced with a litany of complaints along the lines of cars not starting unless the bag of groceries was buckled safely for the trip home, the NHTSA quickly unwound the requirements. Most automakers were even quicker about removing these bastard implementations. However, documentation is usually the last thing the engineering team wants to address, and I'm betting all of the proofs were already completed for the service manuals for the already delayed debut of the 280Z before they got yanked. If the interlock relay did ever exist in a production 75, I would expect it would have the emergency bypass switch like what the 260Z had. More useless trivia: The switch was moved between the early and late 260Zs. On the early (first 12 months) car, the switch is on the right fender, near the battery. On the late (last few months) car, the switch is mounted on the firewall.

Back in the car meet swing with a fully operational Death Star...er, I mean 260Z. Does this count as a Z31 showing up? It was having an out-of-body experience.

This can be useful for early Z cars that don't have a voltmeter: https://www.amazon.com/gp/product/B01M9IKYVH Did the fuse for the fan survive this event? It about sounds like you might have a short in that circuit.

The sender for the water temp on my cars have a bullet connector. Anyway, the crimp on that female bullet connector can be subject to wear from the wires moving from the engine vibrations.

It could be a bad connector at the sender for the water temp. I've had that happen before. The wire got fatigued, and it was almost broken off.

Max doesn't visit this site very often. Reach out to him at the Resurrected Classics website.

I don't have that relay harness, just the stock harness for that circuit. The only issues I experienced with some LEDs is that I had some type 1157 red LEDs fail so that they lit both "elements" at once. I chose a different brand that's in the list and experienced no problems since then. I first started using LEDs over 13 years ago and have no regrets. You may find corrosion in some or all of your side markers. I think that is part of the issue with the circuit overall.