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So I was driving to work in my '75 Highboy the other day (no, it's not my usual commuter car) and the lights started to go dim after about 10 miles. By the time I got there it was just about dead. I was running the heater fan but didn't have any other unusual draws.
Pulled the battery, charged it up and it was putting out 12.8 volts. Put it in, started it up and checked the voltage with it running and got 12.4-12.5 volts. Pulled the alternator and had it checked at the local parts store and they said it checked out fine.
Any idea why an alternator that is supposedly good is only putting out 12.5 volts?
(By the way, I've been reading all the 3g stuff and fully intend to do that upgrade soon, but for now I'd like to just get this one working like it should.)
Thanks for the replies. Is there a way to check the operation of a voltage regulator or do I just have to try a new one?
Also, it's very possible that I hooked things up incorrectly since I'm very green in this area. I attached a pic to show how I had it hooked up. Does it look correct?
Last edited by smg65; Jan 2, 2016 at 12:55 PM.
Reason: pic too big
Thanks for the replies. Is there a way to check the operation of a voltage regulator or do I just have to try a new one?
Also, it's very possible that I hooked things up incorrectly since I'm very green in this area. I attached a pic to show how I had it hooked up. Does it look correct?
What do you mean by 3g. I just got my truck back from the shop, have a brand new battery in it and drove it home 15 miles tops. Died on me as I was braking on the exit ramp. Would not crank. So I figure after charging the battery to pull the alternator and voltage regulator and replacing them. Any thoughts.
what do you mean by 3g? Just picked my truck up from the shop drove it home about 15 miles away, it died on me as I was braking on the exit ramp to my road. would not crank. I figure alternator and or voltage regulator. The battery is brand new. Any thoughts, thanks
what do you mean by 3g? Just picked my truck up from the shop drove it home about 15 miles away, it died on me as I was braking on the exit ramp to my road. would not crank. I figure alternator and or voltage regulator. The battery is brand new. Any thoughts, thanks
Four hole 95 amp/Two hole 130 amp Ford 3G alternator swap.
Do yourself a favor no matter what alternator you have or want installed, make sure the cables and ground connections are clean and bright and shiny tight and you're getting all the electrons you paid for.
Just a couple few hundredths of a single ohms resistance will cut the output of the alternator by a third! Unless and until you've made some serious effort at replacing the cables and cleaning all this stuff up it's guaranteed to be worse than that on a 40+ year old truck.
Maybe won't notice it on a sunny day but once you start running the heater motor and headlights, it will not be able to keep up. A little bit of corrosion can eventually cost hundreds of dollars in batteries, alternators, regulators, switches, etc.
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