electrical gremlins?
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Freshman User
Joined: Mar 2011
Posts: 25
Likes: 0
electrical gremlins?
I'm really hoping someone can help me. I have a 79 ford f150 4x4. I'm having this weird intermittent problem with the dash/tail lights. So here is what's going on. When I drive with the headlights on most of the time everythings working great but then suddenly the dash lights start blinking along with the tail lights and marker lights. And while all of this is happening the headlights get dim and bright. And I know it ain't the alt cause its brand new and I've shut off the truck and left the lights on and it still did it. So does anyone have a good wiring diagram or any suggestions. It would be most appreciated thanks :-)
Cargo Master
Joined: Oct 2010
Posts: 2,674
Likes: 16
From: Ideeho
Hving gone thru this problem myself, I think I can help. First, I think you have ground issues. Clean up both ends of the ground cable that run from the battery to the block. Then install a good heavy (8-10 guage) ground wire from the block to the frame. Then one from the frame to the cab sheetmetal and if you want one from the frame to the bed sheet metal. That will probably fix 99% of your issues, it did on mine. For a while.............The next issue I ran across is the connector on the engine side of the firewall that runs to the tail lights. Follow your tail light wiring from the rear back up to the connector on the drivers side right near where the harness comes thru the firewall from inside the cab. If you trace it out, you'll find it. Disconnect the connector and clean the contacts in both sides of the plug. Mine was corroded and would drop contact occasionaly. I'd bet that will take care of your issues.............I figured out the ground issue fairly easily because my headlights would get brighter when I would step on the clutch.......It was grounding thru the clutch linkage apparently............
Senior User
Joined: Jul 2005
Posts: 494
Likes: 0
From: Mountville PA
let me offer a different opinion you have a wire in the parking light circuit chaffing on metal somewhere, had the same thing happen to me, but it was in the headlight system, everytime it does it do you here a click come from the headlight switch? Thats the internal circuit breaker in the headlight switch. Check for bad insulation on the wires going through the rad support and through the bed to the taillights. If you still can't find it when it does the blinking next time start unpluging the connectors at each front corner and the rear under the truck they will be 4 wire square plugs.
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
Sounds like a short causing the internal circuit breaker in the headlight switch to cycle. Check for damaged insulation as suggested above. A ground issue is not likely to be the culprit, because ground issues cause less current to flow. The headlight switch is interrupting because more current is flowing than should.
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Post Fiend
Joined: Apr 2008
Posts: 8,261
Likes: 15
From: Big Sky Country
Just to rule it out as a possible cause, be sure the voltage regulator is securely mounted i.e. grounded to bare sheet metal.
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