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About Danl

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  1. What I am learning is that this test is NOT necessarily adequate in modern vehicles. At least in this 2012 Honda Civic, it seems that the power regulation system is pretty sophisticated. The voltage the alternator system puts out depends on the charge state of the battery. So it you have the system connected to a fully charged battery, you won't see any voltage increase at all. So when the battery gets drained, the right thing to do is to test the alternator THEN, as opposed to after you've installed a new, and fully charged battery, which is what I did. The belt tension can't have anything to do with it, unless the charging system isn't working. It is. The shop connected a power system analyzer to the battery, wherein you get load curves, battery status, and charging efficiency.
  2. So this is funny. My wife's car wouldn't start. Bad battery. Battery was eight years old. Installed a new battery, and it all starts fine. But I say, hey, I'd better check the alternator to make sure it's charging. So I put my DVM across the battery, when the car is running, and it reads 12.5V. Hmmm. I turn off the car, and it still reads 12.5V. That says to me that the alternator has gone south. I'm looking for 14V when the car is on. So we take it to the shop, and they scan the electrical system and ... alternator is fine. The whole electrical system is fine. Whaaa? I've always tested the alternator by looking for a higher voltage across the battery when the car is on, than when it's off. If that's the case, the alternator is good. Is that not right??
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