I have a 6 cylinder John Deere engine with a Bosch alternator, trying to figure out the purpose of the D+ connection. The wire going into the D+ connection is through a reverse biased diode and then connects to an output from the Engine Start Outputs Module on the ECM (in other words the diode is shown in the diagram to be forward biased from the ECM to the + connection). The set-up leads me to believe that the D+ connection is an input from the ECM that provides excitation to the Bosch alternator (through a slip ring?) - right now I'm only getting a 0.4 VDC input to the D+ terminal from the ECM and a 12.2 VDC reading on the B+ alternator output terminal - please let me know if I'm looking at this incorrectly and/or if all is well with the readings I've taken...can't lose the engine out here as I'm down to a single generator on a remote island in the Bahamas - numbers on the alternator are 1 197 311 032 EL 14V 783 - the number stamped on the alt housing is 785 thanks!!
I'm pretty sure that terminal is for the warning light and
also used when testing the exciter diodes.
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Can you give the engine serial # XXXXX can look it up and provide an accurate answer for you. What is the make of the genset thanks Kevin
Engine Serial No. is PE6068T533312
Another number just below the Serial No. is 6068TF150
The Bosch 14-volt alternator is a 12-pole, self-induced synchronous generator. The current coil is located in the stator, and the exciting coil in the rotor. The exciting current is supplied by the rectifier (terminal D+) through the regulator, two carbon brushes and slip rings to the exciting coil in the rotor.
The alternator generates alternating current which is then transformed into direct current by the rectifier diodes.
The alternator windings are Y-connected. The coil ends U, V and W are connected to the rectifier diodes. The current flows through the diode and terminal B+ directly to the positive pole of the battery.
Alternator current is generated in each stator coil (B) of the alternator. During one revolution of the rotor, the voltage in the stator coil rises form 0 to the positive maximum, drops to 0, rises to the negative maximum and again drops to 0. Then the process is repeated.
As the stator coils are Y-connected, a three-phase or alternating current is generated. The individual phases are shifted 120 degrees.
A sealed electronic regulator is used to regulate the alternator voltage. This regulator, which cannot be adjusted, limits the alternator voltage to approximately 14 volts.
Appears to me that your altenator has failed due to your troubleshooting.
If I can be of more help let me know kevin.
Hi I do not know what scale your meter is on but with key on and engine not running D+ should be battery voltage, and B+ should be 2-4 voltsWhat about engine running? Both D+ and B+ should be charging voltage (14)There is another marked W Switch your meter to AC and running that should be 7.63 AC Volts. What is your problem? Has this been setting?Thanks Johngot more questions, fire backIf this helps please click accept.
OK, I can't turn the engine off as it's my sole source of power out here - with the engine running, I get 12.2 VDC on B+ and only 0.4 VDC on D+ - the connection from D+ BACK through what would be a reverse biased diode (makes no sense to me) all the way to the ECM is through the Engine Start Ouputs Module (not input module), which again makes no sense to me....I'll measure AC volts at W and get back to you...appreciate the response, getting alot of them so hard to keep up in a timely manner....
We've been holding at 12.2 volts for hours (since I reconnected leads from ECM to D+ that had been disconnected by my crew while I was off the island, so there may be nothing wrong)...I don't recall ever having much more than 12+ VDC output from the alternator, but since this is a newly installed one AND since I've only this generator to rely on for now, I wanted to be sure...
The module for engine start you are refering to senses voltage from the D+ to prevent you from engaging the starter while the engine is running quite a complicated curcuit to preform this simple task. The low voltage on the B+ terminal would make me want to replace the altenator since it is your only source of power, or atleast have one on hand being so remote. KevinB39838.0931345718
Cat Field Tech for 6 years, John Deere Field Tech For 5 years