pulsing lights

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Jul 9, 2005 | 03:12 AM

Grok

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Joined: Jun 2005

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From: San Francisco CA

pulsing lights

Every bulb in the truck pulses together. Headlights, dash lights, break lights... and when the motor revs increase so does the pulse. (at idle its about as fast as the turn signal flasher but when the motor and pulsing lights speed up the turn signal stays steady) It does this all the time and its not the glowplug relay I checked the current and they stop when the motor is worm. Now, before I got disconnecting everything one fuse then wire at a time chasing this any of you have any possible causes and how/where to check. I'd appricate it since I'm flying blind with no manual. This is happining to an 86 F250 6.9L 4x4 with some whack trailer brake amd light wiring.

Thanks for the help,

Dylan

Jul 9, 2005 | 06:20 AM

PLC7.3

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Joined: Nov 2004

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From: Manitoba

My first thought would be the voltage regulator is cycling, on your truck that should be on the pax fender, a silver box. What is the battery voltage truck off, what is it with the engine running at 2000 rpm and does it peak. Most voltages are 12.5 at rest and 2 volts higher running so 14.5. Try running the engine and put on all appliances ie lights, fan, radio etc to see what the voltage is then. Post back with the info.

Jul 10, 2005 | 09:04 PM

Dave Sponaugle

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Joined: Nov 2003

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From: Nutter Fort, WV

Sounds like the batteries (one or two) may be getting weak. Another good possibiltiy is you have a connection that needs cleaned in the battery system somewhere. Grounds, positive terminals, negative terminals, on the passenger side inner fender there is a smaller wire that feeds electricity to the cab, starter solenoid, glow plugs and lights. Corossion on that wire at any of the connections can cause the same symptoms.

Jul 14, 2005 | 03:03 AM

Grok

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Joined: Jun 2005

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From: San Francisco CA

Hi,

Thanks for the toubleshooting ideas. I have the following info:

-Had both batteries tested and replaced the bad one. Now the lights are steady at idle but start pulsing around 1200-1600rpm.
-voltages:
--12.8 at motor off on pulse
--11.9-12.2 motor off glowplugs cycling (didn't check for visible pulse)
--14.1-14.3 around 2k (dash lights pulsing)
--14.3-14.7 lights on at idle (no pulsing)
--12.3-14.5 lights on at 2k (lights pulse)

Then I cleaned the terminals on the voltage regulator (silver box inside passanger fender). In the same location I cleaned a black relay that trigers the starter solenoid, it gave me trouble a week ago. BINGO! No more pulse and no more bouncing voltage readings. I get 14.2 steady lights on or off idle or at 2k. All connections were somewhat corroded and are better for the cleaning but, I suspect it was the yellow wire on the voltage regulator. It was many times worse than the others. I wonder what that wire is connected to/does? May have also been the dirty gournd to the cap.

Thanks for the help allways appricated,

Dylan

Jul 14, 2005 | 04:46 AM

fellro86

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Joined: Feb 2004

Posts: 11,697

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From: Marengo, Iowa

I think it is full time power. Without going and looking, that is my guess. I had to clean that one recently myself. I used dielelectric grease to keep it from happening again. My probelm was taht the regulator had totally failed. I also had problems with maintaining contact on the energizing wire to the alternator.