77 280z 2 seater, I recently did a distributor upgrade, bypassing the voltage regulator and my car was running much better, however Ive noticed an as issue my car has been having a few times and it is becoming more frequent. whenever i put a strain on my battery (such as turning the lights on), my voltage drops to 0 lights turn off, nothing comes on, however, my car still turns over and starts, after which everything works fine, but its charging at 16 volts with the charge light on like the bat is disconnected, then when i stop, turn everything off, and remove the load, the bat reads 12 volts and everything seems fine, until i put a load on it again (sometimes even a tiny load like my interior LED lights). I checked battery, starter, alternator, fuseable links, and fuse box, all SEEMS fine (its the middle of winter so i havent had a chance to check with a volt meter yet no broken or lose connections though) but im not sure where to go from here. I dont wanna fry my electronics by driving with a high voltage everywhere, or have my electrical connection die to where i cant start my car.

Any idea where to start with this issue, im going to go out and recheck the terminal connections tonight to make sure theres no rust under it, but other than that given how my car reacts where would you start?

Also i dont have maxi fuseable links yet.

A second issue i have is my heater core is undergoing electrolysis and getting holes, where are common electrical grounding areas that can cause this, and whats the best way to fix it?

Did you mean alternator upgrade rather than distributor upgrade?

It sounds like the internal resistance of the battery is much higher than it should be. When you measure an unloaded battery with a meter, the meters input resistance is many times higher than the internal resistance of the battery, so virtually little voltage is dropped across the internal resistance and almost all is dropped across the meter's resistance.

When you put a load on the battery, if the load resistance is equal to the internal resistance, half of the voltage is dropped internally and half is dropped across the load, ie 6volts would be measured across the terminals with the load inplace.

Pull you battery out and get it tested as your local parts store. They can tell you if the battery is finito or simply discharged.

Yes I meant alternator upgrade, sorry, im going to upgrade the distributer this tax return.

The battery is only a year old, but one of the diodes on my old alternator went out and wasnt charging it right, that might have killed it, but I didnt think it could kill it in that way, Ill have it checked out tomorrow.

Edit: Also keep in mind the problem is intermittent, it does it more at night when cold when i put a heavy load on the battery without the car running (turning lights on and such). But has not happened in a day or so.

Edited January 4, 201312 yr by Xenn

Sorry for the late update, got the battery tested, its fine, since we've had warm weather the problem has gone away. I am still stumped.

It sounds like the internal resistance of the battery is much higher than it should be. When you measure an unloaded battery with a meter, the meters input resistance is many times higher than the internal resistance of the battery, so virtually little voltage is dropped across the internal resistance and almost all is dropped across the meter's resistance.

I am voting for bad internal regulator in the alternator. It is not uncommon at all to get a bad alternator from the parts house. Hell, one time I went through three in a row! During that episode, I learned to basically do this:

1. Test the Alternator while still in the car, Load and No Load.
   
2. Have the auto parts store test the alternator in the car again.
   
3. Have the auto parts store test ANY alternator you buy BEFORE leaving!
   
4. Drink Beer.
   

Good luck!