You need to start a new question, and PLEASE! List the engine size and mileage. This was an old conversation between a few people, and as you can see, when you piggyback on it, no one is going to see it or have a chance to reply. That does you a disservice. On our list it shows up as having received a reply already.
This is not an alternator problem. It is working too well, and that is the fault of the voltage regulator or the wire going to it. The regulator lives inside the Engine Computer and does not cause much trouble. The place to start is by monitoring the voltage on that control wire while the problem is occurring. Its important to know that if the voltage regulator circuitry is totally shorted inside the computer, it is incapable of drawing the voltage down to 0 volts. The lowest it can go is around 2 - 3 volts. If you find the voltage dropping to 0 volts, that wire is rubbed through somewhere and is grounding out.
There's two small terminals on the back of the alternator. They will only have voltage while the engine is running. One will have full battery voltage on it. It's the other one you need to monitor. It will have less than battery voltage, but should not have 0 volts. Typically you'll find between 4 and 11 volts. The lower that voltage, the greater the difference is between the two of them, and the stronger the electromagnet will be.
Monday, February 27th, 2017 AT 12:10 AM