Need to test ground wires
My beautiful 05 Pontiac bonneville gxp is giving me electrical issues unfortunately. Interior lamps turn on and off randomly sometimes with the brake or windows being used so I pulled the fuse for now. When I lock and unlock it no longer honks or flashes lights, and if it sits for bout a week it slowly dies and I need a small jump but starts fine daily. Do I have a bad ground or grounds somewhere ?
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From: Windsor, Ontario / Detroit, Michigan









You can check for parasitic battery drain using the instructions below. You also might want to pull the front seats (easier than you think), pull the carpet (again, easier than you think) and look for corrosion on all of the wiring and connections you expose. There are a significant number of electrical circuits, junctions and control boxes under the carpet (including the ground buss), and if you have any water leaks they tend to corrode.
1. Disconnect the negative (black) terminal from the battery.
2. Plug the black wire for your multi-meter into the "Com" port on the meter, and the red wire into the appropriate port for reading Amps. Make sure it is Amps, not mAmps, and the meter is capable of reading up to 3 Amps. Set the multi-meter to read Amps.
3. Touch the black wire from the multi-meter to the negative terminal on the battery, and the red wire to the disconnected negative battery cable, thereby completing a circuit.
4. The multi-meter will likely show amperage when initially connected because you "woke up" the electrical system when you made the connection. Wait for a few seconds up to a few minutes for the amperage to drop back down as the electrical system goes back to sleep.
5. If the multi-meter continues to read over 25 mAmps after the electric system goes back to sleep, there is a parasitic draw. Go to the next steps.
6. One by one, pull, observe the meter, and replace each fuse and relay in the fuse panel(*) (many vehicles have more than one fuse panel) until the multi-meter shows the amperage drop to an acceptable level. Start with circuits that control lighting, anything in the instrument panel, and the infotainment system. Once you find the fuse or relay that causes the amperage to drop, you have isolated the suspect circuit.
7. From the owner'* manual, determine which electrical devices are on the suspect circuit.
8. One by one, isolate each electrical device on that circuit by disconnecting the electrical connector that feeds it, observing the multi-meter for a drop in amperage, and reconnecting the electrical connector if no change in amperage is observed. If the suspect circuit is controlled by a relay, keep in mind it could be the relay itself that has failed to release and is keeping the circuit live.
If all the above fails to locate the faulty circuit, the final step (I actually do this first) is to disconnect the main power cable from the alternator and observe the amperage. The alternator could have a failed diode that can cause electrical power to short to the alternator case, and therefore to ground. This will drain the battery quickly.
By the way, before you start looking for parasitic draw you should have already checked the alternator and the battery. If you haven't, check the alternator by reading voltage across the battery terminals with the engine running to make sure it is in the 14 to 15 volt range. Check your battery by taking it to Autozone or another automotive parts store, and they will load test if for you for free.
1. Disconnect the negative (black) terminal from the battery.
2. Plug the black wire for your multi-meter into the "Com" port on the meter, and the red wire into the appropriate port for reading Amps. Make sure it is Amps, not mAmps, and the meter is capable of reading up to 3 Amps. Set the multi-meter to read Amps.
3. Touch the black wire from the multi-meter to the negative terminal on the battery, and the red wire to the disconnected negative battery cable, thereby completing a circuit.
4. The multi-meter will likely show amperage when initially connected because you "woke up" the electrical system when you made the connection. Wait for a few seconds up to a few minutes for the amperage to drop back down as the electrical system goes back to sleep.
5. If the multi-meter continues to read over 25 mAmps after the electric system goes back to sleep, there is a parasitic draw. Go to the next steps.
6. One by one, pull, observe the meter, and replace each fuse and relay in the fuse panel(*) (many vehicles have more than one fuse panel) until the multi-meter shows the amperage drop to an acceptable level. Start with circuits that control lighting, anything in the instrument panel, and the infotainment system. Once you find the fuse or relay that causes the amperage to drop, you have isolated the suspect circuit.
7. From the owner'* manual, determine which electrical devices are on the suspect circuit.
8. One by one, isolate each electrical device on that circuit by disconnecting the electrical connector that feeds it, observing the multi-meter for a drop in amperage, and reconnecting the electrical connector if no change in amperage is observed. If the suspect circuit is controlled by a relay, keep in mind it could be the relay itself that has failed to release and is keeping the circuit live.
If all the above fails to locate the faulty circuit, the final step (I actually do this first) is to disconnect the main power cable from the alternator and observe the amperage. The alternator could have a failed diode that can cause electrical power to short to the alternator case, and therefore to ground. This will drain the battery quickly.
By the way, before you start looking for parasitic draw you should have already checked the alternator and the battery. If you haven't, check the alternator by reading voltage across the battery terminals with the engine running to make sure it is in the 14 to 15 volt range. Check your battery by taking it to Autozone or another automotive parts store, and they will load test if for you for free.
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