My Alternator has at excessive Voltage

[Wotname]

Thinking aloud here -

Most internally regulated car alternators are N type.
AFAIK, the RE57 regulator is a P type.
If the alternator was an N type and RE57 is a P type, presumably the AE modified the alternator accordingly, if not, it might have never worked properly.

[Wotname]

Originally Posted by Oceanride007

Thanks Matt. Around 12.6 Volts. Should have mentioned that.

Actually I anticipate your next comment, am now going to separate the Brown wire from the field. See what I get.

Ahh... is this the 12.5V mentioned earlier?

If you are getting 12.5V on the D+ terminal of the RE57 but getting 15V at the battery then there is a fault in the wiring between the D+ terminal and the key switch. There is 2.5V dropped somewhere. A drop of say 0.1V is acceptable but nothing greater than 0.2V.

To test, run a wire directly from the D+ terminal of the RE57 to the battery +ve post. If the output voltage is now regulated to around 14.4 or less, then the wiring at the D+ terminal of the RE57 is faulty.

If the output voltage stays at 15V, then the RE57 is faulty or it is connected to the alternator incorrectly.

[sinnerman]

My 55 amp automobile-type "no-name" alternator (westerbeke/universal/kubota 3 cylinder 21 HP diesel) ..
has an adjustment on the regulator to set the voltage. see picture

cheers

[Oceanride007]

Well, think I got it.

Unfortunately as sometimes happens, "design drawing" differed from "As constructed" in this case, there was additional wiring that somebody had put in, If that wiring mod was known then fault finding would have reveiled that there was a open circuit between the control Diodes and D+ of the Regulator. D+ was not seeing the Output voltage and was sending excessive field voltage out. I knew the wiring was there but had no idea how it did it. The alternator could not be taken apart to trace the wiring. The Regulator must have been powered by the Brown wire from Alternator failed light.

Thanks Guys.

[GILow]

Glad to hear it is sorted.