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Hank F.
Hank F., RV tech - emphasis on gensets
Category: RV
Satisfied Customers: 14995
Experience:  RV tech since the beginning of the millenium.
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I have a 1999 Fleetwood discovery rv with a 6500 LP cummins

Customer Question

I have a 1999 Fleetwood discovery rv with a 6500 LP cummins generator model # ***** nhm-fa/26116h the generator runs but does not put out 110 electricity. when I replaced brushes I noticed the one of the slip rings had very minor scratches so I polished up and ohm checked getting 22ohms. I have tested the harness side wires on the inside of the control box and found when I ohm between J4 9-10 I get 28 ohms. when I check voltage on the wires they all start around 2v and they climb until the vehicle starts. there is not an exact number. the j4-7 climbs to about 9.8 volts the j4-9 climbs to about 23v after starting and j4-10 going to about 22v once it fires. slip ring showed 20.2 volts. when I tested the the brushes connecting right side to solenoid and and the other to a good ground I got 18 volts while cranking. I am not sure if the regulator is the problem or the slip rings after testing the current system.
Submitted: 2 years ago.
Category: RV
Expert:  Hank F. replied 2 years ago.
Hello, my name is ***** ***** I am going to assist you with this.Your field is testing out as good, so the problem won't be in the brushes, slip rings or rotor. I would like you to do this, and let me know what happens.Remove the wires from the brushes, paying attention to which wire goes to which brush. Insulate the wires so they can not touch ground.Make up 2 jumper wires that will attach to the brush terminals, and install a 5A fuse in one of the jumpers.Connect the fused jumper to the positive (right hand) brush, and to the battery post of the starter solenoid.Connect the other jumper to the negative (left hand) brush, but do not connect the loose end at this time.Set your meter to VAC, and connect the negative lead to a good ground. Connect the positive lead to the back of the circuit breaker.Press and hold ‘Start’. While holding ‘Start’ (or if the engine actually starts), connect the loose end of the second jumper to a good ground. There may be a large spark when you connect it, but the spark will not hurt you.With both jumpers connected, check the output voltage. It should be between 30 and 50 VAC.How much voltage is there?.
Customer: replied 2 years ago.
Which circuit breaker....the one above the start stop switch?
Expert:  Hank F. replied 2 years ago.
Yes, the one inside the control box of the genset..
Expert:  Hank F. replied 2 years ago.
Have you tried this yet?
Customer: replied 2 years ago.
yes I got 1.8 volts when I did the test
Expert:  Hank F. replied 2 years ago.
If you are only getting 1.8V out when applying 12V directly to the brushes, it is not a good sign. It indicates a possible bad stator, so lets test it.
To test, you will need to remove all stator leads.
The leads come out at the top left corner of the control box. There should be 4 large wires and 4 small wires.
Carefully note where all wires are attached and remove them.
The T1, T2, T3, and T4 are attached to the terminal blocks at the rear of the control box.
The Q1 and Q2 are attached at the voltage regulator. Simply unplug the voltage regulator.
The B1 and B2 will have an inline connector before they get to the control board. Disconnect these 2 connectors.
Set your meter to ohms and record the following readings, I have posted what the readings should be:
T1 - T2 0.327 ohms
T1 - T3 infinity
T1 - ground infinity
T1 - Q1 infinity
T3 - T4 0.327 ohms
T3 - ground infinity
T3 - Q1 infinity
Q1 - Q2 2.089 ohms
Q1 - ground infinity
Let me know what you get here.
Expert:  Hank F. replied 2 years ago.
Have you tested the stator yet?
Customer: replied 2 years ago.
when all wires unplugged i get
t1-t2 .1- .4 ohm never settles just bounces
t1-t3 not showing change
t1- ground not showing change
t1-q1 no change
t3-t4 .3- .5 ohm
t3- ground no change
t3-q1 no change
q1-q2 2.3 ohm
q1- ground no change.
Expert:  Hank F. replied 2 years ago.
Those readings aren't all that bad, but they're not good, either.
Due the fact that you get no output voltage when jumping 12V directly to the brushes, your next step is going to have to be to remove the stator, and inspect it for damage.
Expert:  Hank F. replied 2 years ago.
Have you checked the stator yet?

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