1994 Dodge

Tiny
RS121R
  • MEMBER
  • 1994 DODGE RAM
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 200,000 MILES
Enter your question.I Have a 1994 3500 Dodge that Im not getting power to one of the poles on the Gen have checked the alt, braker and its good.
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Thursday, February 10th, 2011 AT 12:25 AM

7 Replies

Tiny
CARADIODOC
  • EXPERT
Are you saying you have battery voltage on one field terminal and 0 volts on the other? If so, the brushes are worn. They can be replaced fairly easily. I can post photos if needed.

Caradiodoc
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Thursday, February 10th, 2011 AT 3:41 AM
Tiny
RS121R
  • MEMBER
No main line from battery is hot. But there are two pole on the back of the Gen that when you turn the key on, one of the poles will have power. But when you start the motor the it should excite the field to make more then 12v( mind you this is a new rebuild Gen bought today from a shop that I have dealt with for years. With no issues.
And the one gen that was taken out was installed 200 miles ago.
Is there a Rely switch other then the 120 amp fuse.
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Thursday, February 10th, 2011 AT 5:40 AM
Tiny
CARADIODOC
  • EXPERT
Measure the three voltages on the alternator. The fat output wire must have full battery voltage all the time. One of the small wires must have battery voltage and the other one should have less but not 0 volts. Those last two will only be there for one second after turning on the ignition switch, then they will come back when the engine is running. Holler back with those numbers.

Caradiodoc
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Thursday, February 10th, 2011 AT 6:18 AM
Tiny
RS121R
  • MEMBER
When the key is turned on, the Volt meter showed 800 to 900 Dc mV,
I tested one at a time and they each showed this. But only when the key is turned on.
The fat wire from the the battery has full power to it 11.98 Volts all the time.
When the motor is running they are hot. But still it only puts out under 12 V
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Thursday, February 10th, 2011 AT 4:53 PM
Tiny
CARADIODOC
  • EXPERT
What are the exact voltages on the two small wires when the engine is running?
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Thursday, February 10th, 2011 AT 5:28 PM
Tiny
RS121R
  • MEMBER
916.32 Dc Mv But only when the key is turned on. (Not Running)
Nothing when key is not off. With motor running 11.89 Dc. Each Pin and or wire.
Battery is @ 11.90 V
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Friday, February 11th, 2011 AT 12:21 AM
Tiny
CARADIODOC
  • EXPERT
11.89 volts with the engine running means the voltage is getting there from the automatic shutdown relay. That stands to reason because that's the same circuit that feeds the ignition coil and injectors. Since the engine runs, we know that circuit is working. The answer comes from the second terminal. Since the voltage is exactly the same, no voltage is being dropped across the field winding. That means no current is flowing through it and no electromagnet is being developed.

There are only two possibilities. The voltage regulator circuit inside the Engine Computer is defective or the wire going to it is open. It's more likely you'll find a broken wire. The next test is to measure the voltage at the Engine Computer. The wire is dark green and is in the middle of the three connectors. (I have to use a '96 service manual but I think the circuit is the same). There's three rows of pins. The dark green wire is the second from the end of one of the outer rows. There might be a protective cover that must be popped off so you can back-probe the wires, but don't totally disassemble the pins from the connector because they're real hard to put back together.

If you find voltage at the computer, the regulator is defective. You can verify that by grounding that wire with your back probe. That will cause the alternator to "full-field". Do that just long enough to verify battery voltage goes up. You'll hear the alternator strain too.

If there is no voltage at the computer, there is a break in the dark green wire. Start by looking for any connectors or places where the harness might be rubbing. There's also a splice in that wire. It's in the harness just to passenger side of the cruise control servo, and just to the right of where that harness makes a "Y".

Caradiodoc
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Friday, February 11th, 2011 AT 1:54 AM

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