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Jared D
Jared D, ASE Certified Technician
Category: Mazda
Satisfied Customers: 1812
Experience:  Shop Supervisor at County Fleet
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I'm working on a 94 Mazda B4000. The battery tests good and

Customer Question

I'm working on a 94 Mazda B4000. The battery tests good and I just put on a new alternator but it still doesn't charge.
Submitted: 1 year ago.
Category: Mazda
Expert:  Jared D replied 1 year ago.

Note the operation of the battery indicator light on the instrument cluster. It should be illuminated when the ignition switch is in the run position with the engine off. When the engine is started, the battery indicator light should go out.

If the battery indicator light is not illuminated with the key on, engine off, disconnect the voltage regulator connector at the alternator and ground the Red/Light Green (R/LG) wire to determine if it results in illumination of the battery light.

If the battery light illuminates when the R/LG wire is grounded though it did not illuminate when the voltage regulator connector was connected, either the circuit is not making good contact to the "I" terminal of the voltage regulator connection, the alternator has a faulty case ground, or the alternator is defective.

If the battery indicator light is on with the key on, engine off and it stays on when the engine is started, disconnect the voltage regulator connection to verify that the light goes out. If the light stays on, it would suggest the R/LG wire is grounded in the harness between the cluster and the voltage regulator connection.

If the battery indicator light goes out when the voltage regulator connection is unplugged even though it stayed on after starting with the voltage regulator connector plugged in, check for hot-at-all-times power on the Yellow/White (Y/W) wire of the voltage regulator connection and the Black/Orange (BK/O) wire, B(+) terminal. Check the two power supply circuits with the circuits connected and the engine running for full battery and similar voltage readings.

If the voltage on the Y/W wire is found to be low compared to the BK/O wire, check for an issue of the Y/W wire running to the 15 amp alternator fuse of the engine compartment fuse box and address it as needed. The Y/W wire runs through C113 between these two points.

Expert:  Jared D replied 1 year ago.

Here is the connector pin out view if you need it.

Expert:  Jared D replied 1 year ago.

Please let me know if you need additional info.