B7100 Dyno Troubleshooting

[jparasho]

I don't seem to be getting any voltage output from the dyno on my B7100. After cutting for several outings the battery on this tractor gets weak and will not start tractor. When I check the output of the dyno ( the 2 blue wires out of the dyno I am showing No voltage). The dyno is moving freely while tractor is running. Could the regulator be bad? If the regulator is bad would I still get a reading on the output of the dyno? Kubota dealer wants to replace the regulator but also is not sure if this is what is causing the problem. I am beginnning to doubt them on their diagnostic skills. Any help will be appreciated. Jim p

 

[ibnxe]

I think you are going to find that the output of the Dynamo is alternating current. Check it with a voltmeter, set to AC. The regulator is where the current is rectified and regulated... AC in and DC out.

Connect the voltmeter across the battery, start the engine and see if the voltage rises above 13 volts. If not, something is not working. If you were getting AC out of the dynamo, but no rise in the battery voltage, the regulator is suspect.

 

[jparasho]

output on dyno is 3.1 volts ac and doesn't vary at high rpms or low rpms voltage on battery is 12.3 and doesn't vary i am getting 8.3 volts ac into regulator but nothing out. just had this dyno replaced 3 weeks ago by the kubota shop in our area when i had a cracked head replaced. dyno was bought used from one of their mechanics in the shop. when i went back to them they told me this mechanic was no longer working for them and that they would go back in and check everything but that i would be responsable for all labor and parts. not real sure i wont to do business with them again. lesson learned i guess thanks for the help

 

[ibnxe]

I went out this afternoon and did a couple of measurements on my dynamo. After disconnecting it, measured the winding resistance. The resistance measured 0.4 ohms. Started the tractor with the dynamo still disconnected from the wiring. At idle, voltage was 14.5 volts AC. This voltage climbed to about 36 volts AC at full speed. Your low measurement may be due to shorted diodes in the regulator. Was your reading taken with the dynamo connected or isolated?