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2003 Hummer H2 6.0L Alternator Upgrade

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Hello, all.


I have installed several sets of off road lamps (14 55w 12v lamps in total) on my H2 (Same engine set up as a 2001-2006 GM 2500/3500 Silverado/Sierra) , and notice a power draw when I have all of them on at the same time (lights dim etc). It has been recommended to me to install a more powerful alternator to compensate for the new power needs, rather than going with dual battery set up at this time. I believe the factory alternator is a 145amp Delphi. What is the power output at idle (500rpm)? I am looking at replacing it with one of two aftermarket alternators rated at 225amp and 250amp. Which would be better for my application? TIA.







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Calculate your amp load at idle and look at the charts for each alternator.


The 250 amp alt. on Amazon says it makes 100 amps at 550 rpm.


Post a question on the Summit site to find out how many amps the 225 amp unit makes at idle.



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For the 300 amp, did you have to put on a non-factory belt? Is the pulley on the 300 amp alternator the same size as the factory belt?

Factory size belt for the 145 amp alternator

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