520H 30 amp fuse

[emjay 0]

I've been trying to solve this one.  Recently acquired 1990 520H and I have the wiring diagram.  No tach and not charging with blown 30 amp fuse.  Started to put a good fuse in and sparks flew.  Yup, battery voltage across the fuse socket.  The circuit is short and simple, just to the voltage regulator/tach signal generator.  Pull the center wire off the regulator and now fuse would be okay.  Bought a new regulator before further checking.  I was hoping the old and new regulators would have different characteristics but both have continuity from the center terminal to the right one with both polarity, and there is full isolation to ground.  Since everything to this point is hot all the time and not controlled by the ignition switch, l suspect it will be a short to ground. (forgot to check)  Is that the way it should be or is there something wrong around the stator?  I need to check again but I think the wire to the center terminal is red but should be yellow.  It may have been re-wire, but it behaves as if it is downstream from the 30amp fuse just the same.  What's my next step?

Thanks.

[nylyon-(Admin) 7,842]

On my 416 the center terminal of the regulator has a red wire.  This red wire goes to the 9-pin connector and mates with the tractor white wire which goes to the 30A fuse.  The other engine red wire is the +12v and that runs to the 30A (other side) and also powers the 25A.  Next step is trace wires and test the stator

[nylyon-(Admin) 7,842]

Download this, it has all the answers:

 

[Bill D 2,203]

Take the stator wires off the regulator and test each wire for continuity to ground.   There should be continuity between the wires but not between the stator wires and engine block. 

[gwest_ca-(File Mod) 11,386]

One of the AC leads is connected to the DC+ inside the regulator so a stator winding shorted to the block would blow the 30 amp fuse.

[emjay 0]

Thank you for the properties of the AC leads. There is continuity with about 3 ohms and not grounded.  I did find the the old regulator has 3000ohms to ground but the new one is isolated.  That might do it. 

The stator reading of 3ohm might be .3.  New to me multimeter.  I'll check back later before I try it in case someone thinks there might be something else.

[Ed Kennell 41,308]

to the 

[emjay 0]

Put in the new rectifier and there was still 12 volts across the open fuse socket with the center wire connected.  Connected the AC wires but this time when putting in the fuse there were no sparks.  Fired it up and now the tach reads and there is 20+ VAC across the AC wires and the voltmeter was almost in the green.  I forgot to measure the DC output.  I'll do that when I get it out.  It has a front end loader and the hood only opens so far.  Next on the list will be checking the test switch since it's not working.  Thanks again.

[emjay 0]

Confirmed the voltage at the battery is 14+volts.  The test switch was all corroded but manage to clean up the contacts inside to at least be able to test all the lamps.  I know the oil pressure, parking brake, and motion control circuits are working.  I have a working unit.  Now to change all the fluids and filters and fix the attachment for the counter weight.  This will be a fun toy.