Pulsating lights help

Discussion in '6.9L IH & 7.3L IDI Diesels' started by sailingjacobe, Aug 7, 2018.

  1. sailingjacobe

    sailingjacobe Registered User

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    I noticed on the new 88 F350, that the lights pulsate while the engine is running. Pulsing gets faster as throttle is applied, but at RPM cruising no pulsing I can see.

    Ive cleaned the grounds, My guess is the alternator is bad.
     
  2. Thewespaul

    Thewespaul Supporting Vendor Supporting Member

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    Pulse on and off or just dim and dimmer?
     
  3. sailingjacobe

    sailingjacobe Registered User

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    Lights get dim and and dimmer. as well as the battery light on the dash cycles some times.
     
  4. Thewespaul

    Thewespaul Supporting Vendor Supporting Member

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    Check you voltage with the truck running and raise the rpms while watching the meter. It should be pretty smooth in the voltage change as the alt puts out more amps at the higher rpms. If you see nothing out of place with the voltages, then I’d check the connection on the back of the headlight switch.
     
  5. sailingjacobe

    sailingjacobe Registered User

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    all the lights pulse, not just the headlights(actually I dont think the headlights pulse since the last owner put in HID) But at higher RPM the voltage goes up, and the pulsing gets a little faster.
     
  6. Thewespaul

    Thewespaul Supporting Vendor Supporting Member

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    All the lights in the truck pass through the headlight switch
     
  7. sailingjacobe

    sailingjacobe Registered User

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    Oh okay, Ill double check. Cause I cant remember if it does it with the lights off or not. MY cb radio goes crazy when Ive been driving at night. But I dont remember if it does during the day. Ill check when I get to lunch break.
     
  8. Macrobb

    Macrobb Full Access Member

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    I had this before, it was either alternator, regulator(you have a 1G alternator, right? External regulator on those). or grounding to the regulator.
     
  9. sailingjacobe

    sailingjacobe Registered User

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    Has the external Regulator on the passenger fender.
     
  10. franklin2

    franklin2 Full Access Member

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    I have had this before too. It was a loose connection on the small two wire connector on the alternator in my case.
     
  11. typ4

    typ4 Supporting Member Supporting Member

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    You may also have a bad diode in the alternator, pulsing at idle is normal, at higher speeds its not.
     

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