battery drains out overnight

2003 BUICK CENTURY
91,000 MILES • 3.1L • 6 CYL • 2WD • AUTOMATIC
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TEAM49
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Battery draw using amp meter is 1.7 amps across battery negative. Pulled fuse for cluster, HVAC, radio, etc., and amp draw drops. found shift indicator light stays lit all the time. Thought issue was in cluster but tried it with different cluster with same result. thought BCM was bad so plugged another one in, and did not change issue. Could you tell me what controls the prndl light or help me find a readable schematic?
Feb 18, 2021 at 12:53 PM
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KASEKENNY
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Just want to confirm the scale of the meter was in amps and you have a 1.7 amp draw and not milliamps. If you do then I get why the battery is drained overnight as that is a large draw.

If you have a 1+ amp draw then I would suspect that is more then just the PRDL lights. The other reason is they are feed from the headlamp switch. So we need to narrow down the possible causes from that fuse that you unplugged to get it to go away.

Do do this we need know everything that is on it including other fuses and start removing components one at a time.

I suspect if you unplug the bulb for the PRDL then it will drop some but not all the way down under 30 milliamps.

If it were me based on this info, I would unplug the headlamp switch and see what the draw does. You may have a shorted switch which is leaving the interior illumination circuit on. That would account for the 1+ amp draw.

https://www.2carpros.com/articles/car-battery-dead-overnight

Let us know what you find. Thanks
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Feb 19, 2021 at 2:36 PM