Q: 04 Avalanche "Battery Not Charging" even after new battery, alternator, ecm, and clean cables.

asked by on March 11, 2018

Truck gets a message: "Battery Not Charging" and the battery light comes on. New battery was installed, and the light went away for a few days. It came back on again so the alternator was replaced. The light went away again for a few days. The light came back on so the ECM was replaced and all battery terminals and the ground were cleaned and secured. Today the "Battery Not Charging" light is on, might go off briefly, but comes back on. The battery voltage drops from 14 to 12, then 10. There was one time the battery died completely. Need some help identifying where else this problem can come from.

My car has 150000 miles.
My car has an automatic transmission.

Confirm that there are no parasitic loads while the car is both idle and running. The grounding of the alternator should be checked. If grounded through the block, make sure all engine to body grounds are adequate. The actual output of the alternator should be measured at the battery terminals and if no obvious wiring issue exist, and there are no parasitic loads, you can record alternator output, on a data logger, to get some insight into what the cause is. There are other steps (from the Factory Service Manual) and to have the cause identified, please request an electrical diagnostic and the responding certified mechanic will get this resolved for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.

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