Battery or alternator

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Jan 3, 2008
Medellin, Colombia
I have a 1963 FJ40 with an F1 Engine. After changing to an electric fan, my battery discharges if I drive the car with lights on (100 watt halogens) at low rpms (30 -40 min downhill)

I have a 550 CCA battery that has been checked and is ok and a 50Amp alternator that has also been checked and ok.

I know one (or both) has to be changed so the system can provide the energy required for all the draw that both lights and electric fan produce.

Any help or :idea: on deciding which one to try first (alt or bat) would be apreciated. :crybaby:
Getting an alternator should be your first step, the hope would be that the alternator can support the electrical loads you have and maintain the charge on the battery. The battery helps with the surge load of the fan starting but shouldn't have to run on battery once it is spooled up.

You will need to know how much draw you have with lights, fans, etc then base your alternator size on that.
I would start with an upgraded alternator if the battery is discharging while driving, also I may be wrong but 550 cca seems like a amall battery for a cruiser.

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