Hot Rod Forum : Hotrodders Bulletin Board - View Single Post - Hot wire and fuse on aux. fan switch
View Single Post
  #2 (permalink)  
Old 06-18-2006, 09:48 AM
docvette's Avatar
docvette docvette is offline
Hotrodders.com Moderator
 
Last wiki edit: Rebuild an alternator Last photo:
Join Date: Mar 2004
Location: Lafayette, california
Age: 62
Posts: 7,362
Wiki Edits: 12

Thanks: 0
Thanked 6 Times in 3 Posts
Quote:
Originally Posted by rapsag
I have a custom built car (Chevy 350 drive train) with an auxiliary fan 130 watts at the front of the radiator. It is just set up with a manual toggle switch at the dash and powered by a 14 gauge lead from a hot terminal under the dash. There is a 25 amp fuse in the line. No relay. When I flip on the switch, the wire and fuse will gradually get hotter and hotter until almost untouchable. I always have switched it off at that point (usually don't need the cool fan for long anyhow), but have never let the fuse blow, which I am sure it would do. The toggle itself does not get as hot in comparison to the fuse and wire leading to it so I think it can handle the heat. The fuse in on the battery side of the switch which I assume is correct.

So what may be the problem? Poor ground from the fan? I know that having a relay is desirable but would that change the problem? Need a heavier gauge hot wire? Hot wire directly from the battery? Any advice appreciated.
rap
Doc here,

Your courting a fire in the making..

!4 gauge wire is way under rated for the draw your fan (s) are pulling..for starters.

The switch is most likely under rated as well..most "off the shelf" switches are rated at about 5 amps continuous contact ratings..

You need to install a relay, and 10 gauge wire.

A Fan may "Spike" many times it's rated value under certain conditions. Start up for one..That current that is required for the fan to overcome gravity..Rotor lock is another (a plastic bag sucked up off the roadway) , It can cause multiples of it's regular draw..Obstructions to the air flow..the possibilities are endless..
  • Coil power to your switch now.
  • Coil ground to a good bonded hard ground.
  • 10 gauge wire from a Proper fuse link Directly from the battery or solenoid to the normally open contact on the relay.
  • 10 gauge wire to the fan motor from the relay center wiper.
  • 10 gauge wire to a good hard ground from the motor.

This will end your heating issues, it will deliver more power to the fan motor, be properly fuse linked, and your car will be less likely to catch on fire.

Doc
__________________
Aftermarket Solutions
Electronic & Electrical
Innovations
Reply With Quote