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Alternator,regulator,voltage drain ... help!!


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Well, I have searched and searched, but did not find anyone else with the same symptoms that I have...

Anyway, here is the situation. My daily driver 280zt has had a voltage drain for years. Whenever the car is turned off, the gauges (stock volt meter, fuel gauge, temp, etc) all still have power and stay on. I remedied (bandaid-ed) this by adding a battery cutoff in the car. This has worked fine (except for the rare occasion that I forget to switch it off). It usually takes only 6-8 hours to drain the battery low enough that the car will not start.

Anyway, I noticed that the car was not charging today as I drove into work. I stopped at a buddy's house, bolted in a spare alternator he had, and it showed no change. I went to the auto parts store, picked up yet another alternator (which I had them test before I left the store), and voltage regulator (it's externally regulated and no changes have been made to the charging system).

 

I plugged in the new voltage regulator, and new alternator, and the car would not charge. The volt meter showed 12 volts (verified by multimeter), but all the stock gauges (besides the volt meter) did not work, even when the car was running (not even the tach). I checked all fusible links with the multimeter. I then unplugged the new regulator, plugged in the old regulator and all the gauges worked again, but when the key was turned off, the gauges still remained on. The new alternator would not charge with either regulator and I believe the diode block is getting blown when I plug in the old voltage regulator and switch the battery kill switch to 'on'. I am about to bypass the regulator, install an internally regulated alternator and a maxi-fuse block. I would like to fix the problem before making these modifications, so I do not exaserbate the problem. Any assistance/suggestions are appreciated.

Regards,

Mike

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That is weird Mike. The first thing that came to mind was the ignition switch. On a 240, there is power from the regulator, and ammeter going through the switch, not sure if the 280 volt meter also goes through the ign. switch. If you have a spare, start with that.

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OK, completed the Maxi-fuse block upgrade (eliminating the fusible links and a bunch of unnecessary wiring), installed an internally regulated 280zx alternator (eliminating the external regulator), and results are as follows...

The alternator is still not charging. It has 12.3 volts when the car is off and not running. When the car is running, only 11.7 volts at the alternator. The T-connector going to the alternator w/ the sense wire and the idiot light wire has no voltage running through them whatsoever. Could someone tell me what their voltage to the T connector is? Maybe I can trace the voltage to a source... I am down to physically tracing the wires through the car. More to come as I find things out...

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Yet another update... I found that the gauges all take power from a blue wire which was attached to the external regulator. Gauges need to be connected to this wire with a switched 12V. Alternator is still not charging however, but I am making progress...

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Alternator is now charging and wiring is all good!!

Turns out that the yellow wire going to the T-connector into the alternator (sense wire) is a constant +12V (which I did not have and had to locate a +12V source).

The white/black wire going to the T-connector into the alternator gets a signal from the idiot lamp in the volt meter in the car. I had no signal to tell the alternator to turn on... After swapping Fuel/Volt gauges, to one with a working idiot lamp, the alternator charges properly and I have ~12.7V at idle and ~14.2 or so after 1500 rpm's.

I have been meaning to do the internally regulated alt and maxi fuse block for a while now. I finally was forced into doing it and after an hour or so of driving today, I can find no problems.

BTW, the stock fuel, oil/water gauges all turn off as they are supposed to. I no longer have the drain on the battery when the key is off. That was a short in the voltage regulator.

Regards,

Mike

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