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Relay thermal fan control


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w1r3d 
Member - Posts: 5
Member spacespace
Joined: July 21, 2015
Location: Australia
Posted: July 22, 2015 at 1:00 AM / IP Logged Link to Post Post Reply Quote w1r3d
Hi guys, I have a situation where my ute has had a voltage leak which has in the past given me a flat battery. The ute does not have a pretty history as it has had a engine swap and a supercharger also added giving me 350+ ponies to play with but the wiring side is a mess. So bad that no one can hook up a to the BCM and diagnose any faults.
So I have installed a Master Kill switch so I can guarantee that the battery will not run down but my battery still is not 100% recharged.
I have now got an issue where I go to start the ute after its warmed up but because the radiator fans have been triggered by the Davis Craig thermal switch I don't have enough current to also turn the starter motor.
Solution install 2 fan kill switches to I can control them on start up. I do not want to run numerous wires through the firewall and would prefer to only have the 2 (1 for each fan) My first thought was to use a relay to cut the negative from the fan.
I have wired a relay for each fan with the below pin placement
Pin 30 and 86 - Earth
Pin 85 positive feed from switch
Pin87 negative from Fan
I have quickly tested this but did not have much luck... any Ideas??
Currently I have a manual Davis Craig thermal switch that feeds to 1 relay which connects to both thermal switches
I would also like to have a LED to show when the fan is allowed to run and already have this wired in after the toggle switch(which is the only thing working atm)
All help is much appreciated
w1r3d 
Member - Posts: 5
Member spacespace
Joined: July 21, 2015
Location: Australia
Posted: July 22, 2015 at 1:58 AM / IP Logged Link to Post Post Reply Quote w1r3d
https://onedrive.live.com/redir?resid=CBD889885D94AA2C!289&authkey=!AH4yU4odja6GGFU&v=3&ithint=photo%2cpng
w1r3d 
Member - Posts: 5
Member spacespace
Joined: July 21, 2015
Location: Australia
Posted: July 22, 2015 at 2:00 AM / IP Logged Link to Post Post Reply Quote w1r3d
The above link is how I think it could go.... still not sure if it will work
howie ll 
Pot Metal - Posts: 16,466
Pot Metal spacespace
Joined: January 09, 2007
Location: United Kingdom
Posted: July 22, 2015 at 6:32 AM / IP Logged Link to Post Post Reply Quote howie ll
Best way would be to use an ignition interlock relay, I'll work out some diagrams and post later.
howie ll 
Pot Metal - Posts: 16,466
Pot Metal spacespace
Joined: January 09, 2007
Location: United Kingdom
Posted: July 22, 2015 at 7:03 AM / IP Logged Link to Post Post Reply Quote howie ll
I just looked at the diagram, you have your 85 and 86 the wrong way round., BTW does the thermal fan really switch POS?
Everyone I ever saw switches NEG.
howie ll 
Pot Metal - Posts: 16,466
Pot Metal spacespace
Joined: January 09, 2007
Location: United Kingdom
Posted: July 22, 2015 at 7:07 AM / IP Logged Link to Post Post Reply Quote howie ll
Here you go, use a 70 or 80 amp relay, 87a is redundant in this application, you can use a 4 pin without 87a if it's easier to get:-
fan_switch.png
This will only enable the fan when ignition is on, also you can override the thermal switch if needed.

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