Create 12+ When Ground Is Lost

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alan.c

Member - Posts: 4

Joined: August 15, 2017

Location: Ireland

Posted: August 15, 2017 at 5:09 PM / IP Logged

Hi guy's.

This is my first post, I'm somewhat of a newbie when it comes to car electrics..

OK so basically I'm trying to wire up a radiator cooling fan. The fan thermo switch is a single wire and is grounded when the engine is cold, when the engine gets to up to temperature the ground is lost..

I need to wire up a relay that will allow the cooling fan to come on when the engine is up to temperature.

Is there a simple way to wire this up and with using just one relay?

Thanks is advance

Alan.

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the12volt

Administrator - Posts: 3,955

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Joined: March 07, 2002

Location: Louisiana, United States

Posted: August 15, 2017 at 5:15 PM / IP Logged

Using an SPDT relay, wire as follows:

30 and 85 to ignition 12V+

86 to ground from thermo switch

87a 12V output to cooling fan

87 not used

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alan.c

Member - Posts: 4

Joined: August 15, 2017

Location: Ireland

Posted: August 15, 2017 at 5:24 PM / IP Logged

Perfect I'll try this tomorrow and let u know how I get on.

Thanks

Alan.

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i am an idiot

Platinum - Posts: 13,667

This member consistently provides reliable information

Joined: September 21, 2006

Location: Louisiana, United States

Posted: August 15, 2017 at 5:53 PM / IP Logged

Are you powering the fan with the relay? Or is the relay providing a low current signal to some type of controller?

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alan.c

Member - Posts: 4

Joined: August 15, 2017

Location: Ireland

Posted: August 16, 2017 at 1:09 AM / IP Logged

Powering the fan from the relay

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i am an idiot

Platinum - Posts: 13,667

Joined: September 21, 2006

Location: Louisiana, United States

Posted: August 16, 2017 at 10:53 AM / IP Logged

Cooling fans tend to pull high amounts of current at startup. You may want to use a second relay to power it directly off the battery. Do not connect the single relay to an ignition wire of your vehicle.

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alan.c

Member - Posts: 4

Joined: August 15, 2017

Location: Ireland

Posted: August 16, 2017 at 12:14 PM / IP Logged

At the moment I have it wired directly to the battery via a 15amp fuse and single relay as mentioned above.

I'm not to sure how I'd go about wiring up a second relay

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i am an idiot

Platinum - Posts: 13,667

Joined: September 21, 2006

Location: Louisiana, United States

Posted: August 16, 2017 at 12:27 PM / IP Logged

As long as you have it directly to the battery you are fine. I just did not want you pulling tons of current through an ignition wire.

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