Charging voltage too high

[JimmyC]

The charging voltage on my 710 is too high. I had a bad battery and checked the charging voltage after I replaced it and found it well over 30 volts. I found a break in the black wire between D- on alternator and D- on regulator and repaired it but that did not lower the voltage. I checked voltage on the light blue wire at D+ on the regulator and it is showing the same as charging voltage. My guess is voltage regulator is fried and ordered a new one. Anything else I should look at?

[rmel]

Check to make sure the D+ has a good connection to the regulator.
D+ is what the regulator monitors to set the drive DF to the field
winding. If that's a good connection you just may have a fired regulator.

[JimmyC]

I checked voltage at D+ terminal going into regulator and it matches voltage at battery, B+, and D+. I also unplugged the voltage regulator and inspected connections which looked good.. This makes me think sensing voltage at regulator is correct. I suspect it is the regulator. Should have one late Thursday and will try it. I am surprised the thing would make power with D- broken. I cannot figure out what D- is all about. I know on boats they prefer to have all grounds at a common point. I thought it would be for that, Maybe it is to ground regulator.

[rmel]

Maybe it is to ground regulator.

Possibly, the Alternator is grounded to the engine pretty darn well.
IF the regulator had a floating ground there should have been no
path for current to the field coil. I think your right that your
regulator is bad.

[JimmyC]

I replaced the voltage regulator and all is well. Before cranking the voltage at the batteries was 24.5. After cranking the voltage was 28.1 from idle to full rpm. I suspect the voltage regulator was damaged when the black D- wire broke between the alternator and the regulator. It was very hard to change the regulator.It is held on by two nuts on two studs welded to the chassis. Nuts take a 10mm wrench. In my case the outboard stud was bent. This nut is awkward to get to and impossible to see. I was finally able to get the nut off and then pry the regulator off but it took a longtime. When I got the regulator off I saw the stud was bent. I drilled the weld out and used a bolt and nut instead of the stud. I don’t know why they used welded studs. Bolt and nut seem like a better solution.