Hi,
Is this +12 amps or -12 amps on the gauge? What I mean is, is it reading 12 amps being drawn from the battery, or 12 amps being recharged into the battery?
I'll assume it's the latter? Three amps difference shouldn't greatly affect the operation of the electrical system. No two electric motors are identical, and the new blazer motor might just pull more power due to it's design.
Other possibilities include a loose or corroded connection somewhere, motor not spinning freely (due to lack of air flow or bad motor bearings).
-Nick

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