fan switch in radiator
Thread Starter
Safety Car
Joined: May 2005
Posts: 4,176
Likes: 7
From: Jennings LA
fan switch in radiator
I am in the process of wiring the dual Spal fans on my Dewitts radiator. the switch came installed in the radiator tank. Seems like the radiator itself would need to be grounded. If the switch simply closes at say 195 degrees the control wire for the relay becomes connected to the radiator thru the thread connection. the control wire needs to be grounded to close the relay correct? if it is mounted in the block it goes to ground thru the engine block.
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From: New Or-leens Loo-z-anna
Rookie reply: If the switch has only one wire terminal, it seems the tank would need to be grounded to the frame........
if the switch has two terminals----one terminal would be for 12V+, and the other terminal would go to a frame ground ( or to a fan relay), depending on how the relay was wired into the fan harness.
if the switch has two terminals----one terminal would be for 12V+, and the other terminal would go to a frame ground ( or to a fan relay), depending on how the relay was wired into the fan harness.
Race Director
Joined: Jan 2000
Posts: 12,399
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From: San Jose CA
I would assume the switch is for closing the connection.
IE terminal 1 goes to relay, terminal 2 goes to an appropriate (read: keyed) 12V source. So the relay is energized when the switch closes.
If terminal 1 goes to ground and terminal 2 goes to 12V, as soon as the switch heats up and closes you'll be sending 12V directly to ground.
You could alternately wire it ground to ground, but if you use it for switching a 12V source then you could set it up to always energize the fan when the AC clutch switch is hot.
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From: New Or-leens Loo-z-anna
It definitely depends on how you wire the harness....
Ign. ON/12V to 2-terminal switch...then 12V out from switch to relay activation terminal.......(relay directs constant 12V from battery to the fans)
OR
Ign. ON 12V to relay activation terminal/relay ground terminal to 1-terminal switch (relay activates and supplies constant 12V from battery to the fans/radiator is grounded through supplied grounding strap to frame or through fabricated grounding strap)
It is easier to understand when viewing wiring diagrams....
HOWEVER...... since your switch is 1-wire, the easiest thing to do is run the ground wire from the RELAY to the 1-wire switch.
#30 wire......12 gage
#87 wire......12 gage
other wires...16 gage
Have someone confirm this diagram, since I am a rookie....LOL.
Ign. ON/12V to 2-terminal switch...then 12V out from switch to relay activation terminal.......(relay directs constant 12V from battery to the fans)
OR
Ign. ON 12V to relay activation terminal/relay ground terminal to 1-terminal switch (relay activates and supplies constant 12V from battery to the fans/radiator is grounded through supplied grounding strap to frame or through fabricated grounding strap)
It is easier to understand when viewing wiring diagrams....
HOWEVER...... since your switch is 1-wire, the easiest thing to do is run the ground wire from the RELAY to the 1-wire switch.
#30 wire......12 gage
#87 wire......12 gage
other wires...16 gage
Have someone confirm this diagram, since I am a rookie....LOL.
Last edited by doorgunner; Jan 6, 2015 at 08:26 PM.
Race Director
Joined: Jan 2000
Posts: 12,399
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From: San Jose CA
Your new post is good - first post was a little off cuz it reads like you're connecting a 12V source straight to ground via the switch.
Wiring diagram looks excellent. 87 connects to 30 when there's a potential difference between 86 and 85 (you can flip the connections between 86 and 85 with no difference).
When there isn't a potential difference between 86 and 85, 87a and 30 are connected.
Wiring diagram looks excellent. 87 connects to 30 when there's a potential difference between 86 and 85 (you can flip the connections between 86 and 85 with no difference).
When there isn't a potential difference between 86 and 85, 87a and 30 are connected.
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Melting Slicks
Joined: Aug 2012
Posts: 3,487
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From: Titusville Florida
Tom, not arguing with you but I have one of your radiator/fan setups and don't remember a ground strap, do you have a picture. For what it's worth mine seems to be working just fine...
Former Vendor
Joined: Jan 2000
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From: Brighton
I don't have any pictures but it's just a 14ga wire with eyelets on each end. We may have missed your rad but all rads with the switch in the end tank should have a ground strap somewhere. The switch uses the body as a ground and if the radiator isn't grounded, the fans will never come on.
Melting Slicks
Joined: Aug 2012
Posts: 3,487
Likes: 83
From: Titusville Florida
I don't have any pictures but it's just a 14ga wire with eyelets on each end. We may have missed your rad but all rads with the switch in the end tank should have a ground strap somewhere. The switch uses the body as a ground and if the radiator isn't grounded, the fans will never come on.