2 brand new batteries and a brand new alternator. On red wire of alternator I received 14.75 volts and I rec'd 14.35 volts to the battery. Used truck for a couple of hours, then cut truck off. Truck would not crank back up.
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Is it possible you have a blown fusible link? Wiring diagram should show where these are located. You say the small red wire is zero volts with key on. Is this the wire that supplies "exciter" volts to alt? If so, it should be 12 volts at key on I think.
11 1/2 to 12 1/2 is not charging . That's less then battery state of charge , Battery stat of charge should be 12.6 volts , when charging with a volt meter you should see 13.1 to 14.1 volt at the battery posts . Is there a battery symbol lit on your instrument cluster ? Is there battery B+ voltage at the wires hooked to the alternator How to Test an Alternator
How do you know it's only putting out about 1/2 ? an 1/2 what ? Amps or volts ? Did you hook up a volt meter to the battery posts ? red to red an black lead to negative post of the battery ? Does it show 13.1 to 14. 1 volts with the engine running , if so it's charging . The only thing that would cause the alternator not to put out full charge amps would be a bad diode inside the alternator or a power or ground issue. You need to check power an grounds doing a voltage drop test . Voltage Drop Testing the Charging System
by new battery you mean brand new off the shelf in which case the voltage would have been 12.5volts and not 11.5 volts. battery voltage will drop while cranking an engine but should recover to 12 volts when stopped. The alternators charge directly to the battery by the red wire from the back of the alternator to the positive terminal of the battery. The other smaller wires are for the regulator control and charge lights. Take the vehicle to an accredited auto electrician to have the fault rectified.
at alternator gig wire battery voltage,one wire battery volts one less . battery volts wire goes to automatic shut down relay, less then battery voltage wire to pcm fuse will be 20 amp just ck all that size.
Could be anything from corrosion on cables, loose cables, lose or faulty wiring of wires behind alternator
defective voltage regulator. Visually inspect all the items noted. Then use a volt meter and measure the charging voltage of the alternator. It must be between 13,5 to 14.5 volts with and without accessories on at idle and 2000rpm. Anything below 13.5 weak battery or defective alternator ,lose wiring , corrosion. Anything above the 14.5 volts is a defective regulator.
Check the voltage on the White/Red wire at the 2-pin connector on the
alternator. Key on engine off there should be near zero volts and when
the engine is running and the alternator is charging the voltage should
the charging system voltage (13.8 - 14.2 volts). Voltage drop the
alternator case to battery negative. Voltage drop the battery positive
circuit to the Black/Red wire (Large wire on output post) and the
Yellow/Black wire in the 2-pin connector (sensing voltage). Looking for
0.05 volts maximum.
2. Disconnect the 2-pin connector at the alternator when the engine is running and the alternator light is on. The light should go out. If not, then there is a circuit problem (shorted to ground).
use a volt meter while the car is running to check the main wire or large red wire coming off the back of the alternator it should read a steady 14 volts, the volt meter must be set at dc 10 amp settings, ground the black wire to ground or a metal surface some where on the car and touch the red probe wire on the volt meter to the main terminal of the alternator as i said it should read a constant 14 volts if it doesn't the alternator is bad.