TonyT Posted January 13, 2014 Share Posted January 13, 2014 Hi All, I'm new to this forumn. I have a 1980 280zx that is losing power between the alternator and the battery. The alternator measures 14.8 volts (car on), at the battery it measures 13.5, battery measures 11.5 (car off). When starting it's a slow start but once it fires up it runs without cutting off. I unhooked the battery and the car stays on so I think the alternator is good. Could this be a voltage regulator problem or something else? Any help would be appreciated. On another note does anyone know what motor swaps are good for this car? TonyT Quote Link to comment Share on other sites More sharing options...
NewZed Posted January 13, 2014 Share Posted January 13, 2014 battery measures 11.5 (car off). When starting it's a slow start but once it fires up it runs without cutting off. I unhooked the battery and the car stays on so I think the alternator is good. Your battery needs replacing or a good charge. Disconnecting the battery with the engine running can damage an alternator, don't do that anymore. Are you really ready to swap a motor? Quote Link to comment Share on other sites More sharing options...
TonyT Posted January 13, 2014 Author Share Posted January 13, 2014 I took the battery to AutoZone and they did a full charge and said nothing was wrong with the battery however its draining. The car was running and after letting it sit for an hour it's dead again. Could it be something other than the battery/alternator? Quote Link to comment Share on other sites More sharing options...
NewZed Posted January 13, 2014 Share Posted January 13, 2014 14.8 and 13.5 show that your alternator and its internal regulator are working correctly, although that's a big drop between the alternator and the battery. Check for current flow with the engine off. You have something connected to the harness draining power. If you just installed something electrical disconnect it and see if the problem goes away. Quote Link to comment Share on other sites More sharing options...
TonyT Posted January 13, 2014 Author Share Posted January 13, 2014 just checked the battery and alternator with the engine off and I'm getting 11.93 to the battery and 11.94 to the alternator. The alternator is an OEM part and I have an external voltage regulator. No electrical work done on the vehicle recently...just clutch replacement. Could it be the voltage regulator? Quote Link to comment Share on other sites More sharing options...
NewZed Posted January 13, 2014 Share Posted January 13, 2014 (edited) Disconnect the battery and measure voltage again. You're not comprehending what the numbers are telling you. Forgot to say that you should not have an external regulator. Edited January 13, 2014 by NewZed Quote Link to comment Share on other sites More sharing options...
thebruce Posted January 14, 2014 Share Posted January 14, 2014 As stated above, please don't disconnect your battery while running. The charging system seems to be somewhat functional due to the voltage while running (13.2VDC is a battery CHOCK full) If the battery drains flat in an hour it should be fairly easy to find the problem. Find a multimeter or someone with a multimeter and measure the current between the negative chassis terminal (negative disconnected, positive connected) and the negative battery lug. This will give you a figure as to what the draw is on the battery at rest. MAKE SURE to start on the highest A(amperage) setting. If you don't you will probably let the smoke out of the meter. Even so you may blow a fuse in the meter as most series ammeters in multimeters are maximum 10A. A clamp on ammeter would remove most of the risk of smoking the meter. If you do this and find more than .2A draw (still pretty large in this old a car), start pulling fuses one at a time and make note of when the draw drops significantly. Also disconnect any hokey wiring that may or not be fused as this is suspect #1 with ANY wiring problem. If there is no significant draw, try charging the battery and leaving it out of the car overnight to see if it has an internal short. Motor swaps are discussed ad nauseum this site and elsewhere. I suggest searching any combination of; s130, swap, motor, or reading through the forum index of this site until something catches your eye. LS swaps seem popular with every car these days... Good luck! Quote Link to comment Share on other sites More sharing options...
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