3g alternator help needed.

03wr250f

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I swapped my truck over to a 3g alternator a while back. I followed many of the articles i have seen here and a couple other sights over the interwebs. the alternator itself works great. I ended up pulling a couple of alts from the jy when i began. I found one had recently been remanufactured. It had the most life left in it looking at the wear items. I then built my own if you will combining the casing of one alt i had prepped and painted and then installed the alternator winding and such in the case. I then ran a 2 ga wire (copper ring terminals on the ends)from the alt to the fenderwell where i installed a 200 amp scoche re-settable breaker. I then ran a cable from the breaker to the battery. I have been happy with it, but every once in a while it will blow the breaker, with no rhyme or reason. I then have found I need to shut the truck off and it also tends to like to sit for a while, then usually as long as I dont add a lot of draws to the system shortly after startup it does fine. When it pops the breaker it doesn't like to be revved at all right after startup, doesnt like the blower motor either, or else it will pop it. If i give it time to sit at idle and charge and add loads slowly one at a time its fine, but its kind of ridiculous. It also densest always do it. It went 6 months in between doing it. I went on a 1500 mile trip from Spokane to Missoula to glacier and back again and it did not act up. but then it acted up on a 3 mile drive. I havent found a root cause or even an explanation. Anyone have any thoughts? I have replaced the breaker with another scoche 200 amp breaker. Is it not big enough? Voltage regulator in the alt going bad? I take it to oreillys and everything tests great according to their machine. I originally replaced the factory alt because my voltage gauge was reading a little low for my likings. It wasnt until i was committed that I figured out it wasnt reading as accurately as it used to and that it was charging fine and the gauge was slightly off. I just figured oh well, why not upgrade since I already had all the parts and was halfway done. I know most people love their 3g. Mine has been nothing but a pain!!! I want to get it working properly. I also got today a couple of for 175a breakers from 3.0 tauruses as another way to test things, because if thats what they use maybe there was a reason ford didnt use a breaker. I only found one 3.8 v6 and it was in a windstar. the "fuse" on it was simply a very factory looking piece of metal bridging the gap where a fuse should have been. Is that how the 3.8s were wired was no fuse?
Any help is very appreciated!
 

Macrobb

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Yeah, you probably want a "fuse wire" instead - effectively a thin, calibrated piece of metal which won't blow under short overloads, but only if it overloads a huge amount or over a period of time.

I'm not sure what size your alternator is, but I'm pretty sure they can produce quite a bit more than their rated amps when the output voltage is low and the RPM(of the alternator) is high.

Right after startup, your batteries are discharged(somewhat) and they will suck up a /lot/ of power if they can. The alternator regulator just attempts to maintain a constant voltage, so it cranks the field up and increases the output of the alternator to (try to) compensate.
 

03wr250f

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i will try that. the alternator is rated at 130a but commonly know to output around 160a that is why i went with a 200 a breaker i thought 40a of leeway would be enough
 

laserjock

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I had trouble with the breaker popping on mine so I switched to slow blow fuses. I think I put 150 on the alt charge and glow plugs getting rid of the link wires.
 

shawn deere

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Love my 3g!
Do you have an aftermarket volt gauge? I had a wierd thing going on, the throttle cable was grounding out on the glow plug controller. It was intermittent tho. Volts would drop to 'N' on normal.

Could disconnect the alternator and take it for a test drive. Soo if the volt gauge flickeres. Should be able to run a good while with out an alternator if you keep headlights and blower motor off
 

bbjordan

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I used a 120 Amp breaker for mine. It's only popped a couple of times, but there was always a good reason why it popped. No problem, just reset it. :)

I'm thinking somethings got to be wrong somewhere to blow a 200 amp breaker.
 

03wr250f

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Thanks for the responses guys!
I do have an aftermarket volt gauge.
but when the breaker pops you can definetly tell on both the factory and aftermarket gauge. voltage drops big time. no flickering and I do know I can go a long time, I just want to fix it so i really can go a long time.
I picked up some slow blows to day so I may try that!
 

laserjock

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What I found was that the breakers are sensitive to transients that won't hurt anything but will cause the breaker to trip. That's why they used link wires which are basically slow blow fuses.
 

riotwarrior

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250 amp powermaster for my truck..ran 200 amp fuse...save alt before cokk it....never blew a fuse.

Gotta add that beast but being a pivot mount too lazy to swap it as need figure out belt length.

Hope fuses solve yer issue
 

chillman88

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I wondered about a slow blow circuit breaker? I got my fuse and holder from under the battery tray on a late 90s chevy blazer for like $1 no issues yet.

250 amp powermaster for my truck..ran 200 amp fuse...save alt before cokk it....never blew a fuse.

Gotta add that beast but being a pivot mount too lazy to swap it as need figure out belt length.

Hope fuses solve yer issue

Just fyi, when I did my swap on my 91 the belt was too long. I put one in from the "ambulance prep" model which is an inch shorter and might be what I needed. Hasn't been in Long enough to tell yet. Old one was flapping against the pivot bolt and wearing a ridge out of the belt.
 
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