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If the battery warning light stays off, even with the voltage regulator connected, indicates a loss of power to the battery warning light, or an open in the Light Green/Red wire.
Check fuse 19 in the inside fuse box. Make sure it is fully seated and terminal connections are good, and verify battery voltage through it with the key on, from the ignition switch. If OK, check the Light Green/Red wire for an open between the voltage regulator and the instrument cluster.The circuit runs as follows: The Light Green/Red wire comes out of the instrument cluster and runs through pin 10 of connector C158, which is the top connector of the three 40-terminal bulkhead connectors going through the left side of the firewall. From there, it runs through connector C169, a 4-terminal connector at the passenger side of the firewall, under a plastic shield, and near the starter solenoid. From there, it runs to the voltage regulator.If the Light Green/Red wire checks OK, check for a loss of voltage into the battery warning light on the White/Yellow wire, from fuse 19 in the inside fuse box.
Let me know if you need additional info.
Which engine do you have in your expedition?
The fuse is missing?
The under dash fuse box should look like this. I circled where fuse #19 should go.
If it's missing then that is the problem. You will want to replace it. It should be a 10 amp fuse (usually red).
Please let me know if you need any additional info.
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