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Discussion Starter #1
Ok my alternator is a one wire from summit racing. It is a 100 amp and im running two electric fans and an msd ignition. Now when I fire it up after sitting over night I can check the voltage and it reads 13.75 volts while idling. If I drive 15-20 miles down the road the voltage on my meter starts going down very slowly. Once I get back home, driving a total of 30-40 miles its almost at 11 volts on my meter. Its worse if I drive at night with the lights. It drops the meter almost two volts when I turn my headlights on. Is my charging wire too small?? I think its a 10 or 12 gauge and it goes back to the battery(in the trunk). The belt is tight enough and doesn't seem to slip...isnt the alternator supposed to put out like 14.5-14.75? I bought it new through summit and its been this way ever since I got it.
 

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100 amp's should be plenty, you are right,it should be 14.5 or about. Sounds like the internal regulator is not doing it's job
 

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Discussion Starter #3
Is it because my charge wire is too small or should it put out 14.5 no matter the size of the wire? I know I had to upgrade my battery cables when I moved it to the trunk so shouldnt I need a larger charging cable? If I let the car sit over night or for a few hours it will charge back up to like 12.6-12.8 volts. Its a brand new battery by the way. Has 1000 crank amps.
 

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Where are you testing? At the alt or in the trunk? If the voltage is differnt from alt to trunk, wire is too small and could burn up! For a 100a that far I would use at least #6 wire.
 

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Disconnect the wire and check voltage at the alt. output if it's up to par, then it's wire size to small.
 

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Discussion Starter #7
When its just idling though a 100 amp alternator puts out like 50-60 amps right? Could it be that when im driving around at higher rpms, that the wire then becomes too small?
 

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If it goes down after driving souunds like the engine heat my be affecting the regulator. I've got a summit one wire on my chevy it only goes down in volts when the engine idles slow (big cam).
 

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Discussion Starter #9
It only seems to drop off in voltage when im driving. If im just idling in the garage it seems ok and doesnt drop, even though its only like 13.75-14 volts.
 

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Discussion Starter #10
Ive got a 460 with a mild cam and little room under the hood but I had this alternator on a 302 once too briefly and its always read the same voltage.
 

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What is it doing that worrys you? As long as you have enough charge to start the car after driving and head light are nice and bright no problume. After driving a little the battery would be recharged from the starter draw. The car running uses very little amperage, unless headlights are on or mabe a big sound sys.
 

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One of the fundamental problems of the one wire alternator is that it monitors the voltage at it's own output. And yes, if you are running a 10 gauge wire all the way from the alternator to the battery that is MUCH too small. You would be much better served to attach the charging wire at the battery side of the starter solenoid.
 

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Discussion Starter #14
Well my problem with it is that when I do actually drive it for some time it wont start very easily...sometimes not at all. It does drain the battery if I drive it. I used to have it hooked up to the solenoid pos side and someone told me I needed to run it to the battery. I guess today I will get some larger wire and run it and see what happens. If that doesnt work I guess im calling summit to complain once again about one of their brand items crapping out on me. Maybe its just me but I have never had one good item from summit in their brand of things.
 

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you need to run 2 or 4 gauge to your battery, or even 0 gauge. it needs to go to the solinoid 1st though , i agree with that ,
 

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Output voltage should be the same no matter what the current output is.
Have the alternator checked either on or off the car.
Agreed, the 10ga. wire is way too small. 6ga. is what you should use. 10ga. will only carry around 60 amps safely.
Agreed, some of the Summit brand products are junk.
 

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Discussion Starter #17
Ok I will have the alternator checked out and also upgrade the wire...maybe the alternator as well depending on the test.
 
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