Alternator help - Voltage too high

[Marshall Mahoney]

The voltage output on the port alternator on my Cummins 6BTA is to high (14-17+ volts depending on RPM). I had the voltage regualtor replaced -- same problem. When tracing out the field voltage wire on the Cummins harness, I noticed that it has 2 diodes or resistors crimped and shrink wrapped in line.

Are these diodes or resistors? Does anyone know the specs? Are they needed -- why can't I just cut them out and run a wire directly off of my start switch to the field terminal?

As a test, I did just that -- applying voltage directly to the field terminal. Still had high voltage.

Any other troubleshooting ideas?

Thanks

[In Memory Walter K]

Marshall- I don't know if this helps, but I had a situation one day when my alternator suddenly stopped putting out. On inspection (jiggling the wires to see if any were loose or not making contact), I discovered that one felt funny as if it might be broken under the insulation. I thought I'd jut cut it shorter and when doing so, discovered what you did. None of the nearby marina stores even knew what it was. Strangely, perhaps by virtue of it's mini colored stripes, the guy at Radio Shack knew exactly what it was and gave me one to replace mine with the broken wire coming from it. Soldered it into the old wire on one end and soldered another piece of wire to the other, sealed it with a piece of heat shrink, connected it and all was well again. I thought he said it was a resistor, but it was a long time ago. Take your old one to Radio Shack and look for someone who looks like he might know something about the stuff he's selling. Walter

[Harry Babb]

I had the same experience with a portable welding machine several years ago. One simple little diode shut down the whole show.

The guys at Radio Shack can identify the diodes most of the time by the different colored rings and the number of rings around the diode.

The diode costing less than $3.00

Don't think my comments will help your alternator malfunction but Walters post sparked my thoughts.

I am sure interested in what solves the overcharging situation.....hope you post the results Marshall.

hb

[Marshall Mahoney]

For future reference, there are two diodes in series, number N5401. I assume they are in place to prevent a power surge back thru the start circuit. Still having issues after the second voltage regulator replacement. I think it may be the battery. When I flip my parrallel switch, the alternator works correctly. I'll swap batteries as soon as the rain stops...

[Rocky]

Marshall I know you problably figured out your overcharging by now but I was just reading your post with the diodes in series with your field wire harnesses. On my gas engines they were in place to keep voltage from backfeeding from output of alternator through stopswitches on my bridge. If they were not in place, when I tried to kill engines from up there they would not shut down, so I put them back in series. Did you resolve your charging problem?