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Old 09-16-2018, 10:56 AM   #1  
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Default 12v source for heavy draw Spal fan

Upgrading my Spal fan to another with much more amp draw. looking to relay the fan the right way this time. I would like to run some heavy gauge wire from the battery to the relay, but I figure it might be easier to jump someplace from the engine bay . Any thoughts on how I can safely do this without affecting my ECU? Fuse-box/Alt?

- The fan will draw ~30A during start up
- The fan
- Alternator is 100A
- Planning to use the stock fan pigtail +12v input as trigger
- Relay/harness is pre-built from Spal with some hefty wiring (hopefully)

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Old 09-16-2018, 12:37 PM   #2  
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When I wired in a relay setup for my headlights, I tapped into the main bus of the fuse box on the passenger side of the engine bay. Pull the battery lead off, then undo the fuse box and lift it up. There is a red threaded stud in the middle of the fuse box which is the positive bus. Run a lug onto that and happy days.
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Old 09-16-2018, 01:10 PM   #3  
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I made sure mine didn't have anything to do with the main fuse box so it would not further tax the main relay. I ran a secondary wire from the battery positive to the alternator positive post previously. Then I ran another wire from the alternator positive post to a fuse and then my new fan relay for My Spal.
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Old 09-16-2018, 01:19 PM   #4  
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See my build thread for details but I pulled my power off of the main power coming into the fuse box before the main relay and ran to an external relay.
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Old 09-16-2018, 02:06 PM   #5  
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ok - ill run 8 gauge from battery to + alternator post. + alternator post to inline fuse, then fuse to 30 relay.

Hope that works.
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Old 09-16-2018, 06:42 PM   #6  
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Or you could pull it straight off the starter as the starter is fed direct from the battery.
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