John Deere 2240 Starting Problem

[jandjyoung]

I have been battling a starting problem on my John Deere 2240 for over 1.5 years. The tractor is a 1976 and had the original alternator and voltage regulator. I replaced them with a rebult alternator which had an enclosed voltage regulator. There were no instructors on how to wire it up. I connected the "B+" to heavy wire from the old alternator. I left the three wire connector hang free as it previously went to the voltage regulator. After about 9 months, I had starting problems again. Was told to connect a wire to the "D+" terminal of the alternator. This was required to "turn on the alternator". I did that and am still having starting problems. Finally got the schematic and it shows that the "D+" terminal goes to the alternator light (which is not on the tractor). My immediate questions are:
1. Can I change from wiring system with separate voltage regulator and alternator to one with regulator enclosed in alternator simply by diconnecting wires that went to old voltage regulator?
2. Does there have to be an excitation line to the new alternator/regulator or is the large wire connection to the battery all that is required?
Thanks so much for your time and responses.
Jack

 

[Tx Jim]

Was the replacement alternator a Delco one wire alternator? Have you relocated the ground (-) batt cable connection from batt box to engine block or starter mounting bolt????????

 

[jandjyoung]

The alternator was a rebuilt combination alternator/voltage regulator from John Deere. I have not replaced the battery ground.

 

[buckshot721]

Are you getting any power to the battery, when it's running? And can you post the schematic you are using?

 

[jandjyoung]

Thanks for your response. My plan is to disconnect the alternator and check the output when the tractor is running. I have schematics which I will attach:
1. Alt-VR is the schematic with separate components. 21 is the alternator, 19 is the voltage regulator and 22 is a capacitor
2. Comb 1 is the combination unit
3. Comb 2 is text from the manual for the combination unit showing wire 6 details

It appears that my tractor model has both the separate and combination alternator-voltage regulator systems. My conclusions from this information are:
1. The "B+" terminal in both cases should go to the battery via wire to the starter
2. The "D+" terminal in the case of the separate voltage regulator is not used. In the case of the combination unit, this terminal goes via wire #6 to the connector and ends there on pin 11.
Since I do not have a gauge for the alternator, this makes sense.
3. I currently have a wire connected to "D+" but do not know where it goes or where it came from. It maybe that my model had a wire #6 even though there is no alternator gauge and no wire is shown in the schematic. The only other possibility is that it goes to the capacitor #22.

My current plans are to:
1. Disconnect wire #6 from "D+"
2. Disconnect the wire from "B+" , start the tractor and see what the voltage is at the alternator connector "B+"
3. From the schematics, can't see what if anything, could be jumped on the connector which has wires 35, 36, and 35
Thanks for your efforts and time.

 

[Tx Jim]

The alternator was a rebuilt combination alternator/voltage regulator from John Deere. I have not replaced the battery ground.

Can you post the JD part # of the replaced alt.?

 

[jandjyoung]

I do not have the part number of the orginal alternator which I replaced, but the new JD combination alternator/voltage regulator is TY25953. I disconnected the wire on post "D+" and still only had 12.5 volts at the battery with the tractor running. I then disconnect the alternator completely by removing the wire from post "B+" and with the tractor running, the voltage at "B+" was 0 volts.

 

[Zebrafive]

In your first post you state "D+ terminal goes to the alternator light (which is not on the tractor)." By this do you mean the alternator light is NOT "on"? Or you do NOT have an alternator light?

If you are saying you do NOT have an alternator light, I think you do, only its a "battery" light.

The D+ terminal should go this light. There should also be a wire to the other side of this light coming from the ignition switch with power when the key is ACC or ON/RUN. The way this works is when the key is in ACC or ON/RUN and the engine is not running the light will be "ON". When running the battery will be sending approx. 13 volts to the light and the alternator will sending approx. 15 volts to the light. 13 battery volts will cancel 13 of the 15 alternator volts. The remaining 2 alternator volts are not enough to make light come "ON". If the alternator fails the 15 alternator volts will no longer be there and the battery voltage will be able to make the light come "ON"

 

[jandjyoung]

Thanks so much for the input. You are correct I do have an alternator light. I have never seen it lit, so never realized it was there. The bulb must be burnt out or the wiring bad. I think it might explain some of my problem, with the light out, there is no way to get field current to the rotor and the alternator would not work. I think there maybe two problems, the light and a need to jumper from the old voltage regulator cable to the D+ terminal of the combination alternator/voltage regulator.
I really appreciate your comment as it got be looking at the alternator light which I did not recognize existed!
Best wishes.
Jack

 

[jandjyoung]

Thanks everyone for your input. The problem has been solved. I replaced the bulb in the alternator/battery light. I then cut the D+ line going from the old voltage regulator and spliced it so I could put it on the D+ terminal of the new combination alternator/regulator. This allows current flow through the alternator light to the D+ terminal of the new alternator and through the rotor to establish the initial magnetic field for the stator. Now the light comes on when the key is turned on, goes off after a few seconds and the alternator has established a voltage to cancel the battery voltage at the light. I now have 14.6 volts at the batteries when the tractor is running.
It has been very instructive and I have found a new website to monitor.....Nice job guys.
Jack