fans, relays, fuses

Printed From: the12volt.com
Forum Name: Relays
Forum Discription: Relay Diagrams, SPDT Relays, SPST Relays, DPDT Relays, Latching Relays, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=107529
Printed Date: July 15, 2025 at 1:29 AM

Topic: fans, relays, fuses

Posted By: d95gas
Subject: fans, relays, fuses
Date Posted: September 18, 2008 at 10:32 AM

Hi People,

Hoping someone could kindly offer some advice and diag if possible on the following:

Have 2x Spal fans rated at 6.9amp each

Off each of the live side of the fans I will have a fused spur, I then want to wire BOTH to a relay which will switch on the fans when the engine is running.

What relay do I require ??
What amp rating should the relay be ??
Do you think 14amp fuses will suffice ??

Any advice would be really appreciated.

Thanks

G

Replies:

Posted By: i am an idiot
Date Posted: September 18, 2008 at 1:01 PM

A standard Bosch/Now Tyco relay will more than handle the job. When a fan of that size turns on, it will pull substantial amounts of current. Is the 6.9 amps the start-up current, or is it the current drawn once it has spun up to speed? The relay should be available at any auto parts store or your local stereo shop.

Posted By: d95gas
Date Posted: September 18, 2008 at 2:04 PM

I believe the 6.9amp is the value once upto speed, but not 100% on that.

G

Posted By: i am an idiot
Date Posted: September 18, 2008 at 8:10 PM

Try it with the 15 amp fuse, if you have trouble with it blowing fuses, you may have to try a 20

https://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=330-070

Posted By: d95gas
Date Posted: September 19, 2008 at 1:08 AM

Thanks for the info.......Can anyone put a couple of diags together, to do the following:

1. Power up the fans when ignition is switched on

2. Power up fans when Ign is on, BUT, also provide an override switch to switch them on/off at will whilst Ign is on.

Would be much appreciated.

Thanks

Graeme

Posted By: i am an idiot
Date Posted: September 19, 2008 at 4:24 AM

Posted By: d95gas
Date Posted: September 19, 2008 at 4:40 AM

Cheers bud, thats awesome, just what I was looking for :-)

Thanks

Graeme

Posted By: KPierson
Date Posted: September 19, 2008 at 7:56 AM

General rule of thumb is to only load a fuse to 75% so I would recomend a 20A fuse. Also, as mentioned above the fans will pull quite a bit of current at start up, I would suggust using a PAC TR-7 to add a 5-6 second delay before the second fan kicks on.

You could also replace the ignition controlled relay with a frequency switch hooked to either a fuel injector of a coil - thus only having the fans come on with the actual motor is running (I'm assuming the fans are engine related). You could also use the toggle over ride switch with this set up.

-------------
Kevin Pierson

Posted By: 04nata
Date Posted: September 19, 2008 at 11:34 AM

Wow I guess I better check the load rating on my 2 fans that are running on top of my amps, they are just 12 volt 3" fans from the computer store, but I have them tied into the remote amp turn on. I have not blown anything yet (6 months) but maybe I should relay it.