Ford — Battery - Drain Test
Testing & diagnosis
From a Ford service manual — check it applies to your exact model before use.
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Before you start
- DO NOT ATTEMPT THIS TEST ON A LEAD-ACID BATTERY THAT HAS RECENTLY BEEN RECHARGED. EXPLOSIVE GASES MAY CAUSE PERSONAL INJURY.
- To prevent damage to the meter, do not crank the engine or operate accessories that draw more than 10A.
Procedure
- Make sure the junction box/fuse panels are accessible without turning on auxiliary components.
- Operate the engine at least five minutes and exercise systems.
- Allow the engine to sit with the key OFF for at least 40 minutes to allow modules to time out/power down.
- Connect a fused jumper wire between the negative battery cable and the negative battery post.
- Disconnect the negative battery cable from the post without breaking the jumper wire connection.
- Connect the tester between the negative battery cable and the post.
- Remove the jumper wire.
- If draw is excessive, pull fuses or disconnect suspected draws one at a time and note the current drop.
- Check the wiring for any auxiliary circuits that run from the battery; disconnect these circuits if draw is still excessive.
Tools required
- In-line digital ammeter (10A capable, milliamp reading) Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- No accessory system should have more than a 50 mA (0.050 amp) draw
- Many modules draw 10 mA (0.010 amp) or more continuously
Source: Ford service manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.