12v source for heavy draw Spal fan - Miata Turbo Forum - Boost cars, acquire cats.

Engine Performance This section is for discussion on all engine building related questions.
Sponsored by:
Sponsored by:

12v source for heavy draw Spal fan

Old 09-16-2018, 11:56 AM
Junior Member
Thread Starter
iTrader: (1)
Join Date: Aug 2010
Posts: 218
Total Cats: 20
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)

Joker is offline  
Old 09-16-2018, 01:37 PM
Junior Member
Join Date: Aug 2017
Location: Norwich NY
Posts: 53
Total Cats: 13

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.
msmola2002 is offline  
Old 09-16-2018, 02:10 PM
iTrader: (12)
sixshooter's Avatar
Join Date: Nov 2008
Location: Tampa, Florida
Posts: 17,798
Total Cats: 2,065

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.
sixshooter is offline  
Old 09-16-2018, 02:19 PM
Senior Member
matrussell122's Avatar
Join Date: Sep 2016
Location: Seattle
Posts: 908
Total Cats: 99

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.
matrussell122 is offline  
Old 09-16-2018, 03:06 PM
Junior Member
Thread Starter
iTrader: (1)
Join Date: Aug 2010
Posts: 218
Total Cats: 20

ok - ill run 8 gauge from battery to + alternator post. + alternator post to inline fuse, then fuse to 30 relay.

Hope that works.
Joker is offline  
Old 09-16-2018, 07:42 PM
Junior Member
iTrader: (4)
Join Date: Apr 2011
Location: Bay Area- East Bay
Posts: 459
Total Cats: 20

Or you could pull it straight off the starter as the starter is fed direct from the battery.
brainzata is offline  
Related Topics
Thread Starter
Last Post
General Miata Chat
06-25-2018 06:39 PM
Miata parts for sale/trade
12-14-2013 12:08 AM
Miata parts for sale/trade
10-31-2011 08:47 PM
General Miata Chat
01-22-2009 10:35 PM
General Miata Chat
06-10-2008 09:39 AM

Thread Tools
Search this Thread
Quick Reply: 12v source for heavy draw Spal fan

Archive Advertising Cookie Policy Privacy Statement Terms of Service

© 2018 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.