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Discussion Starter #1
ok 85, 351 auto, carbed.
I've got a volt gauge in the truck, fire the truck up with choke on, sits at just short of 14v, will sit fine until the truck gets warm and the idle drops down. pretty much anything above 1100rpm i'll be showing just short of 14v, and as i slow down to a stop the volt gauge will slowly drop, at low idle it will sometimes dip below 12v. the hole time the charge gauge on the dash stays between a half and 3/4. I've went ahead and had the alternator rebuilt as-well as a new voltage regulator...problem still persists ideas/suggestions? perhaps i got a bum regulator
 

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when the guage inside says 12 volts go out and put a meter on the battery and see what it is.

btw your sig picture is too big. fix it before I delete it.
 

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Discussion Starter #4
really? unless i'm missing something my sig takes up less space than yours.

i'll have to check again tomorrow but back a few weeks ago i remeber the batt. showing the same as the gauge
 

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when you put the picture in the max size says 600x150 PIXELS. yours is about 170 something....
 

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u got a bad bat tree... yep i said bat tree,,, im in south east by gawd georgia... how olds your battery tho for real? make sure your belts tight... and look at your wiring too...
 

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X2 at checking the reading on the battery. Also check your grounds. Mine does the same thing even after I install the 160 amp 3g, replaced all cables and grounds. I even replaced sensor to volt gauge. But it reads just fine at the bat. I don’t worry about it and have never had any problems.
 

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Discussion Starter #9
tested it friday when i got home and the actual voltage at the batt matches the low reading on the gauge. Belts are new, but tomorrow i plan to go out tighten up the belts again and clean up all the grounds etc. The batt is pretty new, can't tell u exact off hand but only a year or so.

thanks
 

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Its not unheard of to get a bad voltage regulator out of the box. The cheap shit they pass out at parts stores these days is junk.
 

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Discussion Starter #11
I sorta figured it could be common to get a bad one, my price was like 14$. How much quality can you put into that? Lol.... I'm now sort of wondering If it's not the charging system itself. Today was a bit warmer so I was off coke before leaving the parking lot and at low idel it was fine.... Only when the truck warmed did the problem come back. I'm pondering my electric fan, when I got home I left it running and pulled the fuse on the fan, volts didn't shoot back up to 14 like I would have liked but when I rev'd it they when up above 13 and held. So I may put the stock fan back on and see. On the weekend I cleaned all my grounds even added another and replaced the pig tail into the voltage reg. as its seen beter days( I was able to steal the end off our maverick lol). Driving home last night I was stuck behined a transport and she dropped down to 12, only when I hammered on it to go past did it shoot back up, so Purhaps this isn't just an idel problem
 

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Discussion Starter #12
well, i've tried another new regulator, aswell as another battery....problem still remains....wiring problem perhaps?
 

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how many amps in the electric fan drawing?

And did you ever put a meter on the battery terminals to see the actual voltage?
 

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Did the new alternator come with the pulley? If so, is it the same diameter as the old one? Some alternators have to turn a certain speed to work properly. If your alternator works when the engine is running at higher RPM (when the drive pulley is turning faster) then perhaps you need a smaller pulley on the alternator so it will turn faster when you're running at lower speeds.
 

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what is your idle speed rpms, if they are a little low after the vehicle warms up and your high idle kicks off maybe you could bump your idle just a bit
 

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Discussion Starter #16
I haven't checked what the fan is pulling yet but it has crossed my mined. The alt is my original rebuilt, now i never paid attention to what pully is/was on, but that being said the problem started before the rebuild and remained after, so i know it doesn't fully count it out in theory the problem shouldn't be in the alt imo.. Nothing was changed on the truck before this problem, the truck was just sitting. I did think about the idle and i do prefer mine a bit high (about 900rpm) Another person had mentioned checking the fuseable lines between the alt, I pulled some of the loom off my wires the other day and had a look and someone has replaced a few ends, some connections have some green death and its just not nice, i plan to head to the junkyard on the weekend and fined a decent engine harness on that side and just replace the hole deal and clean up the engine bay :).....If this and checking the fan doesn't work i'll be looking for a one wire alt lol. thanks guys!!
 

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Your model bronco probably retains the 65 amp alternator. It may put out 30-40 amps @ idle.

Did it start after the fan install?
 

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Discussion Starter #18
Fans been in the truck from the time i bought it, wasn't me that put it in. like i say i hadn't really added anything to the truck when this problem arised, I can't remember if it started this before i added my lift, but regardless nothing under the hood was really played with. The truck hasn't died out well driving or had any problems starting (unless the batt. was dead, which after a while it seems to drain out, this truck sits alot.) I forgot to mention i did check batt. voltage at the battery and the gauge shows the same as actual volts.
 

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aftermarket or factory volt meter?

I would try to find a amp clamp and see how many amps the fans are drawing. It could be the fan is starting to go out. Just unplugging the fan will probably not give you a instant increase in voltage, but it should start to go up over a few minutes.

you can also watch the volts and see when they start to drop, is it when the fans come on?
 

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Discussion Starter #20
thats an excellent idea thanks jopes, I'll have to go over and do some more looking into exactly when the problem is occurring, perhaps i can jump the fan to turn on when the truck is cold and see if the problem occurs. Its hard to see the fans in the cabin, and if i recall correctly it charges ok when in park, idle about 1200ish than it was when i drop it in gear and we get a drop to 900ish is when the meter just dives. Its an aftermarket gauge i've watching, the truck dose have the stock charge meter with seems to stay around center where it always was. I suppose at this point i need more testing time, trucks in storage for the winter so its not at home right now.
 
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