parasitic draw?
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Cross-Country
Joined: Oct 2009
Posts: 63
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parasitic draw?
04 f350 5.4: Battery just started dying overnight? Had battery tested it is good. Checked amperage draw at the battery with meter getting 400mA When thru fuses and checked mV across and didnt find anything drawing power? Any other obvious thing i can check to narrow it down? Had the truck running and checked battery voltage had 12.39v an hour later checked again and it was down to 12.09? Thanks for any suggestions
Logistics Pro
Joined: Jan 2010
Posts: 4,085
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Process of elimination.
Did you try leaving the battery unhooked for an extended period to make sure it isn't the battery just discharging on its own? It might 'check' good but it may not actually BE good.
If you've got a way to check amperage draw (which it sounds like you do), have someone watch it while you pull fuses, there should be some under the hood as well as under the dash. Keep pulling until the draw goes to zero. Once it goes to zero start putting them back in one at a time until it goes back up - should be the same circuit.
Once you've narrowed down the circuit you're going to need a wiring diagram to chase the wires - you've likely got an electrical component that is bad, or more likely on an older truck, a chaffed/broken wire somewhere that is grounding out.
Happy hunting!
Did you try leaving the battery unhooked for an extended period to make sure it isn't the battery just discharging on its own? It might 'check' good but it may not actually BE good.
If you've got a way to check amperage draw (which it sounds like you do), have someone watch it while you pull fuses, there should be some under the hood as well as under the dash. Keep pulling until the draw goes to zero. Once it goes to zero start putting them back in one at a time until it goes back up - should be the same circuit.
Once you've narrowed down the circuit you're going to need a wiring diagram to chase the wires - you've likely got an electrical component that is bad, or more likely on an older truck, a chaffed/broken wire somewhere that is grounding out.
Happy hunting!
Laughing Gas
Joined: May 2024
Posts: 903
Likes: 289
From: E TN
To do a parasitic draw test it's best to use a bridge, one of those battery terminal disconnects with the green ****. You want to have the circuit complete and you meter hooked to each side of the disconnect then you open the disconnect. You have to monitor the meter as some things might power down over time.
Lead Driver
Joined: May 2003
Posts: 9,303
Likes: 48
From: Lyndonville, Vermont
Engine running good voltage 14.5 volts at battery....fully charged battery 12.7 volts....did you check all fuses? both places? disconnect alternator and check.
Draw should be below 35ma...
Draw should be below 35ma...
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