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Old Oct 3, 2013 | 07:55 PM
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1977 SuperCab

Good evening,
Lights are dimming whenever I let off the gas and come back up whenever I get back on the throttle. Wondering if it could be the battery or the alternator or something more sinister like the wiring...
Thanks in advance.
 
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Old Oct 3, 2013 | 08:12 PM
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It's usually the battery getting old that causes that.
 
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Old Oct 3, 2013 | 08:16 PM
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Put a multimeter on the battery with the truck running and see what it tell you. Like is it charging the battery?

Sounds like time to pull the alternator and go get it bench tested at the parts store. Make sure they test if with a load on it.
 
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Old Oct 3, 2013 | 08:38 PM
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An old voltage regulator will also cause that symptom.
 
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Old Oct 4, 2013 | 03:10 PM
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Good afternoon,
Sounds like take the time and replace all three? Or just one at a time and maybe it will go away. Or is that a problem that will reappear if not all three i.e. (votage regualtor, battery or alternator) are fixed?
Thanks
 
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Old Oct 4, 2013 | 03:30 PM
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Voltage regulators are cheap. Even if that isn't the problem, it would probably be good to upgrade it to a newer one.
 
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Old Oct 4, 2013 | 06:17 PM
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Mutlimeter test the batt (free), get the alt bench tested (free), replace the voltage regulator first, it should be the cheapest as far as parts?
 
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Old Oct 4, 2013 | 07:05 PM
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Alright thanks ill order a voltage regulator tomorrow and let you know what happens
 
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Old Oct 5, 2013 | 09:00 AM
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If that doesn't cure it there is also a very good wiring diagram on this site that will help you out also.on my crew cab everything was new and still did that,so I tested the voltage at the lights and had about 8.5 volts ford in there infinite wisdom used very small wire in there head light wiring its like 14 or 16 gauge wire and with that diagram I put larger wire in and some relays and my light never dimmed again
 
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Old Oct 6, 2013 | 10:21 AM
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I've always made it a practice to replace the alternator/voltage regulator at the same time. Never had a spike that way.
 
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Old Oct 15, 2013 | 04:08 PM
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Gentleman,
Replaced the voltage regulator, still the same problem had some suggestions. What would be the best approach to tackle next. I have the battery disconnected I am working under the dash right now so now is prime time to pull the battery and change it I guess? Just looking for words of wisdom.
 
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Old Oct 15, 2013 | 04:15 PM
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Yes it would be. LMC has a plug and play upgrade for the headlight wiring that's very reasonable priced. item #47-3660

Truck Parts and Truck Accessories

Did you get the alternator bench tested? You can simply drive it there and pull it in the parking lot and walk in with it, if you only have one vehicle to drive, I've done it.
 
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