12v trigger to disable neg output

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prolsc

Member - Posts: 2

Joined: November 24, 2007

Location: Florida, United States

Posted: November 24, 2007 at 4:28 PM / IP Logged

i have a fan that im trying to wireup in my car. The fan has to have the neg. disabled for it to work. I would like to use the 12 volt power source, from the ecm to disable the neg. side of the fan. Is this possible with a relay? The fan has a constant 12v , and a neg. ground, and has a neg. trigger.

Velocity Motors

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Joined: March 08, 2002

Location: Manitoba, Canada

Posted: November 24, 2007 at 10:09 PM / IP Logged

So you want the ECM switched ignition to turn off the fan ? So that means that when the ECM is off the fan will be on all the time ? Sorry, I don't understand what your trying to do here.

Jeff

Velocity Custom Home Theater

Mobile Audio/Video Specialist

Morden, Manitoba CANADA

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prolsc

Member - Posts: 2

Joined: November 24, 2007

Location: Florida, United States

Posted: November 25, 2007 at 9:21 AM / IP Logged

Velocity Motors wrote:

So you want the ECM switched ignition to turn off the fan ? So that means that when the ECM is off the fan will be on all the time ? Sorry, I don't understand what your trying to do here.

How the fan works, that im putting in the car, has full time power going to it., off a 12volt source. It has2 individual grounds , one from the battery and one from the ecm. In order for the fan to come on, the one from the ecm must be disabled. The fan is out of a toyoto. Its a dual fan set up. The ecm which is in a mustang uses a 12v to trigger. the fan., the stock fan. I need the wire from the 12v out of the ecm to hold a ground until it reaches its temp. , then it activates the fans.

tvcomputerwiz

Member - Posts: 25

Joined: December 09, 2006

Location: United States

Posted: November 29, 2007 at 8:03 AM / IP Logged

ok here you go...

12v trigger to disable neg output - Last Post -- posted image.

dualsport

Silver - Posts: 983

Joined: September 27, 2005

Location: United States

Posted: December 04, 2007 at 11:32 PM / IP Logged

If you measure the amount of current needed for the fan control line to turn off, what kind of value do you get?

Possibly you could just use a diode in series between the fan control and the mustang ecm output, if the output pulls down to ground when it's off.

When it switches on and goes to 12V, the diode would be reverse biased, and effectively opens up the ground to the fan, turning it on.

If your ecm output doesn't pull to ground when off, but instead switches between an open circuit and +12V, you might add a pull down load resistance to do it. Without details about the amount of power the two signals use, it's just a guess at this point.

hotwaterwizard

Silver - Posts: 1,350

Joined: December 11, 2003

Location: California, United States

Posted: December 05, 2007 at 5:50 PM / IP Logged

You just confused me real bad ! 12v trigger to disable neg output - Last Post -- posted image.

Do you need to utalize the Positive 12v output from the ECM to produce a Negitive output for the new fan?

If so a relay can be used as an interface.

12v trigger to disable neg output - Last Post -- posted image.

John DeRosa (Hotwaterwizard)

Stockton California

When in doubt, try it out !

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dualsport

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Joined: September 27, 2005

Location: United States

Posted: December 05, 2007 at 7:01 PM / IP Logged

From what I could make of it, when his fan control line is grounded, the fan remains off, and when the ground is removed, the fan then turns on.

I had a Toyota that did that, where it was done kinda backwards from what you'd normally expect. The fan switch would be grounded when the temp was low, and open circuit when it got hot. So, if you were to remove the connector for the fan switch, it would turn the fan on.

I think the sense of the signal is the same, where high (or open circuit in this case) = fan on, and low (or ground) = fan off.

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12v trigger to disable neg output

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