Dave WM

the 280z with the indicator light has 3 term, a Black common and two others, shorting one to black will indicate full on the gauge, short the other to Black and the light will come on.

ever seen those long springy pickup tools, the ones that have the 4 jaws that deploy with a push button on the end? Maybe that could work its way around. https://www.amazon.com/Flex-Cable-4-Finger-Retriever-Pro-Tools/dp/B006ZEOXJY

the empty light comes up slowly as the thermistor warms up without the cooling effect of being submersed in a liquid. The thermistor resistance stays high limiting the current flow (and thus light from the indicator) current is always flowing thru the circuit but the high resistance of a cold thermistor limits the flow below what would cause the light to be seen. Current flow thru the resistance creates heat, with out the liquid to carry that away the thermistor begins to heat up, the resistance drops and the light comes on. Thermistors are resistors that change value with heat. You can test the resistance with a simple meter. typical will be in the hundreds of ohms IIRC, FSM will tell you. best test is to drain the tank and give it time (couple min even). If it comes on then all you have to do is make sure its set at a level that gets it out of the fuel before you run out of gas. the light comes on rather slowly. One thing to check is make sure the light is not burned out AND its not pushed out of the bezel (mine was the plastic socket had fallen out or was pushed out so even if it came on I would not see it). Test it by shorting the wires of the plug where the sending unit attaches. this will check the wiring, bulb and placement.

Looks perfect on the scale (10-100). I recommend you drain the tank, then put back 1 gallon (you might want to start the car and take it around the block just to make sure 1 gallon still allows the pickup to work), and reinstall. Shoot for E exactly at that point. You can adj by bending the float arm wire but a little there goes a LONG way. I found just minor tweeking a few degrees of vertical on the install of the sender worked perfect, but that was with my side mount, a top mount will be different of course.

No harm in trying the new tank after cleaning but not coating. If its a problem you can always go back and coat it.

any seat upholstery? looking for a bottom.

I gotta get a pic of my condenser, its still blowing cold (yea) but I suspect the dye will be showing the leak growing. It just so darn hot that I can barely get motivated to do anything. I know AL can be brutal, I spent the nite out near Andersonville several years ago for a radio control airplane event in July. Soggy and HOT was the order of the night. Camping out in that is a nightmare.

I have been chasing very minor leaks around the gas tank. The final one was a loose clamp at the output of the aftermarket (skinny) fuel pump. it had those slotted hose clamps by the PO, so I put on some proper FI style. I had already done all the hose clamp under the hood, but did not notice these. The other leaks were at the sending unit O ring (cracked) and the last was at the drain plug. The plugs washer was in bad shape. I did not have a proper fitting replacement, so I had temp used an o ring. That was not really idea so while calibrating the fuel sender (tank was drained) I came up with a tight fitting o ring that also fits the ID of a fibre washer. The captured o ring seems to work very well. I still have to pull the plastic panels to work out the stereo speakers. After that I will have no more excuses to not put in the 5 speed. I did recently hurt my back so I was not in a big rush to do that, Hopefully by the time I get the stereo worked out, the back will be better and maybe it will cool down here. its often in the upper 80s even as late a midnite, you have to wait till 3am for it to get down into the 70's, add in 80-90% humidity and well.. motivation is lacking...

Maybe a different approach may help you. Try putting a light bulb in place of the fuse, then go around to all the lights or other accessories and wiggle them around while someone watches the brightness of the light bulb. Look for changes in the intensity as you manipulate things. if there is rust or some other circuit path that is leaking current, hopefully mussing around with the connectors will disturb it enough to point it out.

A little late to the party, but did the OP confirm the correct lights are in the sockets? If the car has been thru a few owners someone may have decided they needed brighter lights. I would def stop now and at least fix that connector with a new one, no mickey mouse repairs to wiring.

wow, I did not realize the ZX was such a different size.

I think I would rather try and install a 280zx, not sure how different from the Z but can't be any more of an effort than the vintage air kit. I think the ZX has a slightly larger evap and maybe could tie into the existing blower box? (this is for a 240z, if I had a 280z I would just try and find the parts for a 280z). I think Redbird went with the vintage Air on her 280z

don't worry about my ramblings about current rating, I was thinking out loud about how the fuse link works. You do need to make sure you are using the correct OE fuse links, including the correct color coding. When testing the alt by jumping the F to the bat make sure you are only idling, over 16v sounds excessive, adj the idle to 800 rpm and start there, turn on the lights and fan (max). Advance the throttle just a bit stop at 14v (if it goes that high on voltage the alt is fine). Compare he volt meter in the car to the digital volt meter reading at the battery terminal to see if they are close.

He may have smoked a non OE fuse link. The only time I had one fail is when the alt shorted to ground, the wire melted inside the insulation which looked perfect on the outside. I would suggest just buying the OE's they are not hard to find and not expensive (under 10$ for a full set IIRC), try that and see if the issue comes up again. If you smoke the correct fuse link the def have a problem. Smoking a homemade could be simply a incorrect homemade. I have wondered about doing a voltage drop across the fuse link and calculating the amperage across the circuit (I don't have anything that I can directly read the high current, so use the fuse link as a shunt). then compare that to the rate current of the fuse link, the problem would still be I don't know the intended current of the circuit. Was it 50% of the rated current of the fuse link? just don't know.

looks good, but you did not have a battery voltage with engine off, that would have been good to know. Homemade fuse links are ok IF the wire used is designed for making fuse links. You need the proper gauge, and the insulation should be fire resistant. Any old wire of the correct gauge is not good enough if the insulation will combust and start a fire. Does the charge light operate properly?

I watched the video did not see a final outcome with it working (just got to the point where the fan would run). I wonder how it turned out. Its clearly a lot of work, and agree with the issue of drilling holes into the cowl area. I would have make brackets to attach to the factory locations to avoid the risk of leaking water at the cowl. Anyway Clearly a lot of work as would be any solution that involves AC (heck even just replacing a evap in a factory AC would not be a walk in the park). If it was me I would prob try to adapt a 280z system, before going thru all that, but maybe the vintage air would work better. The biggest down side is even if you got it all in (vintage air)and working its still not going to ever be able to vent outside air into the car as the cowl tunnel connection and select door is deleted. I recall my old 240 with the suck thru system was not the best, but I wonder how much of that was due to the status of the system, back then is was relatively new (1980) so I assume the seals in the air handling box were ok, but I did not have proper AC gauges and never really got that into it. Also I wonder if the air ducts and fan were limiting the performance as much as the suck thru design.

There seems to be a lot of confusing things going on here. There is a reason the fuse link burned. Most likely a shorted alternator, Or a intermittent short in the wire harness. I am lost as to what is going on now. I think you should start making videos of what you are doing when getting test results like 16v with the VR bypass (F to Batt). Same with getting reduced output at higher RPM and the built in voltmeter including the action of the charge light when the ign is switch to ON and then after the engine is started. I am getting lost in the narrative.

Yea sounds like the VR possible. they are cheap 30$ on Ebay. If you want I have a video on them Make note of the statements near the end about making sure the plug is clean, I had some green corrosion on the VR plug.

That is indeed odd, less voltage at higher RPM. I agree with Zed Head, make sure you have a good test setup and confirm this is indeed what is happening. A couple more things to consider The car come equipped with a voltmeter and a charge light, do these work? If they do then it should be pretty obvious if there is an issue that would preclude driving until corrected. So Does the voltmeter show more voltage after the engine starts If so then you are pretty much good to go, does it show this odd drop in voltage as RPM increase? Unplugging the F/N plug should make the charge light come on (or go off, not sure how it works) and the voltage should drop. You should hear the difference the F/N plug on and off as the alt should sound different as it loads with the plug in. My 75 has an amp meter which I prefer but the voltmeter can give you the same info as long as you remember the starting voltage before the car engine is running. So with a working voltmeter you can pretty much diagnose with out even using any outside equipment. If its not working then that should be the very 1st thing to address. I would never drive my car if any of the gauges were not functioning properly. I just recently spent some time going thru the fuel sending unit to make sure it was calibrated so I would know how much gas I have.

OP, Don't bother with the F to Batt stuff until you get back to us on what's going on with voltage readings at idle. As far as the process, you unplug the plastic plug on the back of the alt, its the F/N plug with the F/N noted right on the alternator. BTW the N lead is used to energize the charging light circuit, it tells the car the alter is turning. next you rig up a jumper, I used an alligator clip on the F term from the back of the alternator to the Bat terminal of the alternator. Exercise some care here so you don't short the clips to the any part of the alternator as this would ground the Battery and vaporize you jumper, quite possibly giving you a nasty burn for your trouble. use insulate clips. and make sure of what you are clipping to. This fully energizes the Field winding (no voltage regulation) and if you alternator is good it will output as much as it can. Again there is NO regulation so you don't want to rev the engine, just get a reading at the Bat term of the alt and at the Battery post (+).

good point Zed, seems it was that last post about 2000 rpm and 12.07 that made me think there is an issue but as you noted the red results, that is pretty much normal, and inconsistent with the 2000/12.07v. OP you need to nail that down better exactly which is it.

2K RPM at 12.07v sounds like a problem. Fuses 1st then Fuse links, then bypass F to Batt on alt in that order. to see if any improvement. Of course the most obvious is check and clean the battery cables. Does the battery terminals feel warm? I have check the voltage on battery terminals and had 14v on the cable and 12v on the post inside the cable, and a LOT of heat at the junction.

you can also check the continuity of the field (F) and the Stator (Bat) with a meter if you disconnect the wires from the alt 1st. Note the Stator (bat) is connected to the stator coil thru a diode pack so you meter will only show continuity in one direction. here I am showing how reversing the polarity of the meter will show continuity one direction and open the other. In my case the diode pack shorted out, burning the fuse link. You could also have an open diode pack that would not blow the fuse link but would keep the alt from charging.

it sounds like the alternator or the VR, check ALL the fuses in the fuse box (pull them out and check for continuity). review the FSM see the part about bypassing the VR (I mentioned the F to the Batt on the alt). this will tell if its the VR or the Alt. Report back after the F to Batt check. If I had to guess the alt is fried (the smoked fuse link), make sure the fuse links test good as well you cant tell them by looking at them. they can be open and look fine. Just need a few diagnostic test to know for sure, you don't want to start replacing parts unless you know they are the problem.

If its like mine the alt is pretty marginal, I bet your different responses were do to slighty diff RPM's. What is the RPM and do you have air cond? Agree with the belts. Did you replace the alternator? It could be losing some diodes (internal). If the fuse link to the alt smoked then there is a problem, did you find the problem or just replace the fuse link? (its possible the fuse link was bad but not likely). Make sure all the bat/alt/starter connection are good and clean, esp under the bat terminals. You can jump the field coil to the battery connector on the alt to bypass the VR, do not rev the engine with this, and see if the voltage at the battery comes up. If so then it would indicate the VR may not be working. Do not rev up more than about 1500 since there is NO regulation with the F connected to the B on the altenator, if its working and you rev the engine you could overvolt the system and fry your electronics. As I mentioned before, mine is marginal at idle, with the AC on (fan on high), lights on etc... I can barely make 12.5 that is with the fast idle servo engaged (AC) pulling up to about 1k. over about 1.5k and its all fine (over 13.5v and well regulated). So the only issue would be if a sat around idling all the time with the AC on. Yours should have the voltmeter built in (my 75 uses an amp meter), is there a charge lite and does it work properly?