301 A John Deere Industrial diesel

Help needed. Can anyone advise what the four wires on
the voltage regulator connect to. This regulator mounts
under the dash. The unit has an alternator not a
generator. Thanks in advance

Here is something I found that may help you. It looks like YT will not let me post a link to it. Search JD 301B wiring diagram it should show up as a post on another forum. There is a wiring diagram for a 300B, so if it is anywhere close to the wiring on your tractor it shows a Green, Black, Orange and 2 purple wires. And it looks like the wires are in a plug which is common for later voltage regulators. The second post with the diagrams worked better for me on my phone. When I clicked it a tool bar popped up and a square with an arrow up out of the corner showed. When I clicked it the diagram opened as a picture I could view easier. If this does not work for you you will probably have to find a service manual to purchase for your tractor which will have a diagram included. Or maybe someone will come in with other information.

This is the best I can provide due to my lack of access tp a 301A tech manual.

Thank you, I really appreciate your help

Thank you, Much appreciate the help

If all still original the regulator connection is a plug in to the matching connector in the harness located withing the length of the wires on the regulator. If the plug-in connector has been cut off the regulator or from the harness, I will ask if it still has the original Motorola alternator or if someone has installed a Delco. If the alternator has been changed to something other than the original type, the regulator might need to stay disconnected. I have seen that scenario a few times.

I used a test light between the negative battery terminal
to negative battery wire. The light was dull but on. After
installing the new voltage regulator the light was bright
using the same method. Using a multimeter meter set on
AC not DC tractor running it shows 039 . Per a video I
saw it should read 00. Also per this video if the meter
showed voltage using this method the alternator could
have a bad rectifier? Short of pulling the alternator off
and having it tested does anyone have any suggestions
Thanks in advance

(quoted from post at 17:52:07 01/29/22) I used a test light between the negative battery terminal
to negative battery wire. The light was dull but on. After
installing the new voltage regulator the light was bright
using the same method. Using a multimeter meter set on
AC not DC tractor running it shows 039 . Per a video I
saw it should read 00. Also per this video if the meter
showed voltage using this method the alternator could
have a bad rectifier? Short of pulling the alternator off
and having it tested does anyone have any suggestions
Thanks in advance

Click to expand...

Not trying to be a jerk, but my first suggestion is to get a copy of the 301A Technical Manual (JD #TM1088). I have the manuals for my JD equipment, and they have the wiring diagrams and a number of diagnostic tests with what you should get for readings from them; I expect the same type of info is in the 301A TM.

Does it have a Motorola alternator as original? Are the plug-in connectors still on the harness and regulator?

When you had your test light hooked in series with the battery and negative cable, did you unhook the wires from the alternator's output (battery) terminal and see if the light went out? That would be an indication of a bad diode(s).

Did you check the voltage across the battery with the engine running about 1500 to see if it is charging and at what voltage?

No offense taken, I unhooked the negative cable on the
battery and put the test light between the cable and
negative battery terminal (dull light) if the cable stays
disconnected the unit will start after setting for
days/weeks. Ive not disconnected any terminals on the
alternator .
Motorola alternator,
Original plug on voltage regulator was not there when I
bought the tractor years ago.
Battery across the terminals when running is reading 15.5
to 16 volts
Thank you for response and input

(quoted from post at 19:48:50 01/29/22) No offense taken, I unhooked the negative cable on the
battery and put the test light between the cable and
negative battery terminal (dull light) if the cable stays
disconnected the unit will start after setting for
days/weeks. Ive not disconnected any terminals on the
alternator .
Motorola alternator,
Original plug on voltage regulator was not there when I
bought the tractor years ago.
Battery across the terminals when running is reading 15.5
to 16 volts
Thank you for response and input

Click to expand...

Were you able to just plug the new regulator into the tractor's harness or did you have to cut and splice the wires in?

The new regulator had the connector. I used spades to
attach those 4 wires then had to splice the other ends
because that half of the plug was missing.