Hi All: A bit scared right now....Car wouldn't start and I thought battery was dead....Lights and radio came on but wouldn't crank.... Waited for CAA, we boosted and 2nd try it started.....He put the meter on it and said it looks like battery is fine 13V. But was showing a charge of 18V ,,...Overcharging. Literally 2km away from home...pulling into driveway, lights went out and heard 2 fuses blow...dont know which ones, but am worried what I will find tomorrow. Any thoughts? (Alternator was already rebuilt this March for an overcharging issue)....less than 200 miles on it since the rebuild. Its a 1982 GTSi Injected European version.
Sounds like you may have a bad voltage regulator, it should be regulating it between 14 volts to 14.5. Pull the alternator out and have it bench test.
If i recall correctly the alternator picks up the battery voltage via a direct wire from the battery post- check the condition of the wire. If it thinks the battery is not 12 volts it will put out more to get to 12 volts, if your wire or connections are poor it might be telling the alt to put more out as it is measuring say 8 volts
Nope thats only with a sense wire on the Nippon Denso alternators. (and some other japanees like Mitshibushi) (they are also max 15.5V or so, NOT 18V) This is an EU/Bosch alternator with Bosch Voltage regulator and there are several possibility's why the Alternator Voltage is too high: Bad regulator 1 Field Diode is gone (this is how it senses the board voltage) and so the regulator thinks the Voltage is to low>> Alternator voltage k=can go uo to 18V Maybe internal ground of the regulator There are modern regulators that fit the older Alternators! This regulator has a green resistor over the ...hmmm carbon things that hit the collector ...Brushes?... this resistor prevents the regulator to regulate to fast (hi-lo) when the brushes are old and make bad contact, also does it make your warning light function even when the brushes are worn) What is CAA?? Road Patrol?? (I'm Dutch so don't know and sorry for my crappy english)
Oke, don't know exactly how they are, but if there is a sensing wire from alternator to battery + it works as you said. Except the max Voltage is restricted to 15V and a bit. So that wont be the explanation for 18V. the sense wire on the alternator can be connected to any plus to see if it works.. (Not Connected the alternator will put out 15, .. Volt
