Alternator, Voltage Regulator, or Something Else? |
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Alternator, Voltage Regulator, or Something Else? |
yeahmag |
May 4 2022, 11:22 PM
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#1
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Advanced Member Group: Members Posts: 2,422 Joined: 18-April 05 From: Pasadena, CA Member No.: 3,946 Region Association: Southern California |
I'm having an intermittent problem where over 3500 RPM (cruise speed for example) the alternator light will come on. If you LOWER the RPM the light goes out and has never come on at idle even with a full electrical load. I've done the following to try and figure it out:
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yeahmag |
May 5 2022, 05:34 PM
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#2
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Advanced Member Group: Members Posts: 2,422 Joined: 18-April 05 From: Pasadena, CA Member No.: 3,946 Region Association: Southern California |
I just did the test on the D+ side of the light (blue wire) and it goes to 5V. It doesn’t go high…
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Spoke |
May 7 2022, 06:07 AM
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#3
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Jerry Group: Members Posts: 6,991 Joined: 29-October 04 From: Allentown, PA Member No.: 3,031 Region Association: None |
I just did the test on the D+ side of the light (blue wire) and it goes to 5V. It doesn’t go high… When does it go to 5V? It should be at battery voltage so there is no current through the GEN light. Did you check the voltages of the VR and battery? D- to chassis D+ to chassis DF to chassis Battery voltage to chassis Do these tests with headlights on at idle and 3500RPM. If D+ is equal to the battery voltage at low RPM then drops with high RPM, it might indicate some sort of rotational issue. Not on a 914 but I had a car where the alternator would charge at idle then virtually stop working at higher RPMs. Removed the alternator and checked the resistance across the brushes and armature. Got a resistance value then when I spun the rotor, the resistance went way up. Took the alternator apart and cleaned the brushes and commutation ring and the alternator worked perfectly after that. |
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