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With a working alternator your battery voltage should be from 13.0 volts up to 14.9 volts. From your readings I will say the alternator is not charging the battery. Your battery voltage should be 12 volts. Get the battery charged up first. A lot of shops have a newer type of charger that will charge the jell type AGM, Optima Batteries. I would also check your system for a draw. I would disconnect that new head unit you installed. Seems like the problems started with that install.



I had the same idea as you just a few minutes ago about disconnecting things. The battery read 13.30V this time with the jumper cables.


Before that though, I had the multimeter propped up still reading the battery while I turned ACC on and started disconnecting things. I disconnect power and ground to the head unit and wideband gauge. When I went from having no power applied, to power applied, the voltage would drop by around .08V and stick there temporarily. I then proceeded to disconnect power and ground to the head unit and wideband individually. I noticed when I had power connected to wideband, and connected the ground, voltage would drop by around .10 rapidly, then when I took the ground off, it'd climb back up, connect ground, voltage back down and it sticks at a certain voltage. I did the same with the headunit and it didn't have nearly the same symptoms. So I immediately thought the wideband to be suspect.


So I hooked up jumper cables again, started the car, took off the cables and monitored the voltage with the grounds taken off both the headunit and wideband at the same time, but with their power wires still connected, and the voltage was STILL dropping. I took off power to the headunit and same deal. I however didn't take the power wire off the wideband yet, but I figured that'd be a lost cause.


So right now, I'm at a standstill and more confusion. I'll start tracing more wires when I have more free time. But as off now, I couldn't visibly see any exposed wires.


What is the item that you are cooling the "Head Unit"??? Please use the proper terminology such that appropriate advice can be issued. It sounds as though the Alternator is good but the wiring is faulty and not connecting the alternator to the battery properly. Do you have the wiring diagram for the 240Z? What is the "Digital Gauge"??? What does this gauge indicate? The 240Z has the ammeter in series with the alternator and the battery to measure charge/discharge current. What is the ammeter indicating throughout all these exercises? An appropriately charged battery should be slightly greater than +12 volts. When cranking the engine for starting the voltage should not go lower than 8 volts DC. If it goes lower there are bad cells in the battery. When the alternator is initially charging after engine start, the alternator voltage should be +14.x volts. As the battery attains a charge the alternator voltage should taper off somewhat from +14v yet still stay above +12v. The newer alternators need only a small amount of current from the battery to provide excitation for the alternator field to cause it to generate 12 - 14 vdc. There may be an excitation return (2 wire excitation) to ground or battery negative to complete the circuit. Normally the case of the alternator is the return or ground path for both excitation and heavy current to charge the battery. The other heavy post or connection on the alternator connects back to the battery through a heavy current (low or no resistance to current flow) fused wire. Older alternator charging systems had more (complicated) wiring than newer charging systems.


Hope this helps. Will look at the 240Z wiring diagram to see which OLD alternator system wiring IS NOT NEEDED.





Source: Suddenly not keeping a charge.


Waddiejohn: What is or does IPA stand for?? Please advise.


Maybe I should not be bringing this back to life, but I've not been active lately and saw this thread after tuning in again and trying to catch up. I'm surprized that nobody recommended using IPA for maching Aluminium. It keeps the material from galling and welding itself to the cutter and provides a very nice finish.

This is EXTREMELY interesting. Would like to do the same and also fab a duct with a smaller opening to the radiator. The desire is to get aero such that my 240Z is stable at higher speeds and also get VERY good cooling of the radiator.



Ok here is my thread about my revised bell pan. I am taking my experience with the current pan' date=' and expanding on what I have learned from the wind tunnel testing. That is why I have put it in this forum. The belly pan in the pic below has been on the car for about 10 years, and has resulted in the car being very stable at highspeeds beyond 140mph. I am documenting my redesign and extension of the pan. I am also redesigning the airdam itself. I will attempt to resculpt it using fibreglass to cover the front wheels better, and be a bit lower. I have removed my long used lawn edging airdam extension, that has been on the car for about 17 years.







I have started by redesigning my lower rad block off plate. I have done this to improve the fit, and clean up the look a bit.


Next I will begin prepping the airdam to reshape it using expanding foam and then laying fibreglass to blend and bond to the airdam. I hope "while I'm at it" doesn't get the better of me. Once the airdam is modded, I will make a new template of the bellpan. It will be a two piece design, that will end at the transmission. It will stop where ever it will make mounting it easier. I will also likely add small fins going front to back, but I will get into that as I build my mockup.

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