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I just put new alternator on my 2004 Ford Escape, and now my battery light keeps flashing on and off, and it will sometimes stay on. The battery has been checked and is charging 100 % . The alternator is working properly.

What's wrong ?

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    Who checked the battery and alternator, and how was it done? The car's computer doesn't think the alternator is working. I'm not sure if the alternator and voltage regulator are separate parts on that vehicle, but if not, the regulator is suspect.
    – JPhi1618
    Feb 9 '16 at 15:49
  • Welcome to the site. What voltage is the alternator putting out?
    – Zaid
    Feb 9 '16 at 15:54
  • You should list the engine size the circuits are different for both. But in general recheck your work and check the fuses B 120A & 11 15A in the engine compartment fuse box.
    – Ben
    Feb 9 '16 at 21:55
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That sounds like a loose connection at a specific wire. Car alternators have a control output to tell the instrument cluster or the ecu that the alternator is running and generating power. It there is voltage on that wire, the battery lamp is off and vice versa. In allmost all cars it's as simple as this.

Most likely the wire on that terminal wasn't properly mounted when installing the new alternator. You can fix this by yourself. To do so, just look for a contact on the alternator labeled "61" or "D+". It is not one of the big ones with thick wires, but a rather small terminal with a thin wire. Tighten the nut or screw holding at that terminal and you should be fine. Note: Disconnect your battery first, otherwise you could cause a short circuit.

Other possible causes are that this wire is damaged or broken. In that case you have to look for the location where it is damaged and repair it.

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    Great details. Is the "61/D+" label specific to Ford, or is that common on most alternators?
    – JPhi1618
    Feb 9 '16 at 16:49
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    61 / D+ are labels specified in DIN72552. It's a German thing, but I think it's quite common since it's the only "label code" I know. en.wikipedia.org/wiki/DIN_72552 Feb 9 '16 at 16:55
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    That signal output is usually pulled low by the alternator when the alternator is not charging. A bulb is usually connected between the signal output and +12v. If there is a bad connection, then the bulb wouldn't light. If you pull the signal wire off the alternator and the bulb is extinguished, then this will confirm it is not a bad connection. If the bulb lights up, then a bad connection is possible.
    – HandyHowie
    Feb 9 '16 at 17:11
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    @HandyHowie You are right, I forgot about that. I will edit my answer accordingly. The only explanations that involve loose connections are a bad B+ connection or a different battery light circuit. In some modern cars, the light is not connected between B+ and D+ (for example because the instrument cluster has no light at all but a big display). In that case D+ could be connected to a sensor input in the ECU where the voltage is measured against ground. In that case the behavior would be as described. Feb 10 '16 at 10:17

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