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Daryl, Shop Owner, Master Mechanic
Category: Ford
Satisfied Customers: 12549
Experience:  28 years experience, Master Mechanic
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1997 ford f150: I troubleshoot this problem?

Resolved Question:

my 1997 ford f150's battery drains overnight. how can I troubleshoot this problem? thanks
Submitted: 5 years ago.
Category: Ford
Expert:  Daryl replied 5 years ago.

I would start by getting the battery load tested if it passes that it has a parasitic draw below is the testing procedure for testing that.


To test, have the driver's door open and latch shut to simulate a closed door and be able to access the interior fuse box. Next, disconnect the negative battery cable and install an ammeter between the post and the cable end. With the meter connected, momentarily reconnect the cable end to the battery post to recharge the capacitors in the vehicles modules without disturbing the meters leads. You may use a jumper cable to jump from the post to cable end if it is easier. Depending on the vehicle and number of accessories, current draw at this time will be between 110 Milliamps (MA) and 850 MA, (with most vehicles ranging between 200 and 500) for a period of up to 50 minutes. This will be a normal reading until the vehicle enters sleep mode. At this time the draw should be under 50 MA. An input such as a door being opened, a button on the Key Fob or the Remote Keyless Entry pad (if equipped) being pushed, lights being turned on or a key placed in the ignition will cause the vehicle to wake up again which requires another "wait to power down sequence" to start. If the draw is higher than normal before sleep mode or never goes to sleep and fluctuates up and down there would be an input to a particular module commanding some response. To diagnose, start pulling circuit fuses and leave out until you find the one that puts the value at the expected awake mode reading or under 50 MA if the vehicle was in sleep mode and address that circuit. Never pull the module fuses or relays as this will change the values when re-installed.

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