This is my first posting and want to start off by saying hello to all the members here.
I just rebuilt and/or upgraded a large case Ford 3G 130 amp alternator to hopefully produce 200 amp+, but have idle voltage/amperage issues. The parts involved in the upgrade: Replaced the stock 2 lead per phase Ford stator and installed a 240 amp stator with 4 leads per phase, a Regitar rectifier part# RF053HV with (8)70 amp diodes and a Transpo F794HD voltage regulator. I soldered the stator leads to the rectifier with a 200watt iron and used a "heat sink" to keep heat from getting to diodes as much as possible. I assembled the alternator with new bearings and new rotor slip ring(re-used stock 130amp rotor), a smaller 2 1/8" pulley and upgraded the BAT and ground cables to 1/0 ga with soldered-on copper lug terminals. The crank pulley has a 7 5/8" diameter, so I have over a 3 to 1 pulley ratio. With engine running at 1500 rpm fast idle(choke on) the alternator has 14.25V, come down to 850 rpm and the alternator has 13.7V with no loads other than to recharge battery. I let it charge the battery for 5 minutes then load the alternator with the accessories I have which comes to 77-80amps and the alternator voltage drops below 12.75volts with interior lights flickering, bring the rpms up to 14-1500 and the alternator still seems low @ 13.25v(engine/alternator now at operating temp). A stock 130amp 3G will still have 13.7v @ 850 rpm with 77-80 amp load. I "full fielded" the alternator once up to temp with a ground lead to ground test screw on VR and my Southwire meter showed 16.5V, but remove the ground lead and it returns to 12.75v. Have I missed something, still am amateur at alternator rebuilding.
I have looked online, in various areas and cannot find the answer as to why a "supposedly" higher amperage alternator needs increased rpm to produce the same amperage and/or voltage as a lower output alternator, is it the stator the rectifier or a combination of both that requires more rpm for the alternator to supply the same amount of output as a stock alternator. Please advise. Thank you in advance for any/all assistance with this matter. Todd
I just rebuilt and/or upgraded a large case Ford 3G 130 amp alternator to hopefully produce 200 amp+, but have idle voltage/amperage issues. The parts involved in the upgrade: Replaced the stock 2 lead per phase Ford stator and installed a 240 amp stator with 4 leads per phase, a Regitar rectifier part# RF053HV with (8)70 amp diodes and a Transpo F794HD voltage regulator. I soldered the stator leads to the rectifier with a 200watt iron and used a "heat sink" to keep heat from getting to diodes as much as possible. I assembled the alternator with new bearings and new rotor slip ring(re-used stock 130amp rotor), a smaller 2 1/8" pulley and upgraded the BAT and ground cables to 1/0 ga with soldered-on copper lug terminals. The crank pulley has a 7 5/8" diameter, so I have over a 3 to 1 pulley ratio. With engine running at 1500 rpm fast idle(choke on) the alternator has 14.25V, come down to 850 rpm and the alternator has 13.7V with no loads other than to recharge battery. I let it charge the battery for 5 minutes then load the alternator with the accessories I have which comes to 77-80amps and the alternator voltage drops below 12.75volts with interior lights flickering, bring the rpms up to 14-1500 and the alternator still seems low @ 13.25v(engine/alternator now at operating temp). A stock 130amp 3G will still have 13.7v @ 850 rpm with 77-80 amp load. I "full fielded" the alternator once up to temp with a ground lead to ground test screw on VR and my Southwire meter showed 16.5V, but remove the ground lead and it returns to 12.75v. Have I missed something, still am amateur at alternator rebuilding.
I have looked online, in various areas and cannot find the answer as to why a "supposedly" higher amperage alternator needs increased rpm to produce the same amperage and/or voltage as a lower output alternator, is it the stator the rectifier or a combination of both that requires more rpm for the alternator to supply the same amount of output as a stock alternator. Please advise. Thank you in advance for any/all assistance with this matter. Todd
