New battery keeps dying slowly. I get 13.7 volt output at alternator but only 12.8 at battery. Thinking that voltage drop due to bad wiring between alternator and battery. Trying to trace wires but don't have diagram. Getting about 2 ohms resistance from alt to battery. Not sure if that is normal. Any help appreciated.

  • In addition to fuse checking as mentioned, examine three wires; two(?) main ground cables - one between battery negative and chassis, the other between chassis and engine block. The third wire is battery to alternator; this one is always 'hot' with alternator circuitry not drawing power until ignition is turned on (battery light ON) or engine running (battery light off, indicating alternator is outputting all the electrical needs of a vehicle while recharging the battery. Examine cables for corrosion and hardware connections, detrimental to the alternator and battery. Baking soda/water clean.
    – F Dryer
    Commented Sep 1, 2023 at 0:02
  • Just to make it clear, did you take both of these voltage readings with the engine running?
    – HandyHowie
    Commented Sep 1, 2023 at 11:53

1 Answer 1


Look for an electrical box in the engine compartment on the driver's side containing a fuse rated more than 100 amps -- maybe 140 amps -- and see if that fuse is blown. You don't have a good connection between the alternator and battery. Two ohms is not normal. It should be zero ohms.

For any further detail, you'll need to say the Toyota model name.

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