My ammeter started running at about +30 to +45 Amps while driving. At idle, it settles at zero but when the rpm's increase the amps increase. The battery will not hold a charge overnight, and when freshly charged it's good for about a day. The alternator is making a high-pitched whine.
I had replaced the alternator about six months ago. Standard early Ford 3-wire alternator.
I first suspected the voltage regulator. Replaced the voltage regulator and still had a high reading on my dash ammeter.
Battery was going dead, so I put my DMM in current mode and put it in line with the battery to look for a draining current. 0 A. Also, 0 mA. Nothing draining the battery while the car is sitting.
I figured the battery had a bad cell, so I replaced it today. I was surprised to find I still had 23 months of warranty on the old battery. Fired it up and took a short ride, and as the engine rpm's increase so do the amps on my ammeter.
Oh, by the way, I know: ammeters are pretty useless; get a voltmeter. On the list.
So, I put my DMM on the battery to test voltage. 12.5 V with the key off, drops when cranking, but with the engine running the voltage climbs all the way up to about 18V
Shut it down and don't plan to drive it until I resolve this.
I plan to take the alternator down to get it tested, as this is the only remaining item in the charging system. The only other thing I can think of is checking the grounds for continuity.
Anything else I'm missing?
DD
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What causes system voltage to exceed 17 volts?
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