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Radiator fan switch function?

tektic

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Dec 19, 2012
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ronkonkoma, ny
I'm using a stock rad fan sensor... At least I think it is. First off what's the difference between the fan sensor and the ac sensor?

OK, so under normal operations cold its supposed to flow power and hot it breaks the circuit? Or opposite?

I'm trying to connect a relay to what I think is the fan sensor but it is acting very strange.

If this is the case I have to wire:
85 - ground
86 - signal
87a - fan
30 - fuse power

Is that correct?

No that would leave the power in when the key is off..
I'm stumped.
 
Last edited:

tektic

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Dec 19, 2012
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ronkonkoma, ny
That's not the case. Out of the 3 sensors I had two were bad and conducted power at room temp. So I'm going to swap to the third sensor... Fan should be wired to 87 not 87a
 

tektic

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ronkonkoma, ny
Nothing worked so far. I still don't get this... Can someone please explain this to me.
 
Last edited:

transparentdsm

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Jul 27, 2011
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Cherry Hill, NJ
so on your sensor you need the sensor to complete a circuit to turn on the fan. so something would need to tell the relay to turn the fan on, something like a single post that would ground its self out once it hit a temp, the oem sensor is looking for you to complete a path, so i would run a ground wire to the sensor on 1 side from the relay and then off the sensor to the fan ground and make sure the fan is constantly getting power. or switch it around and go power instead of ground. that way when the sensor hits its temp it with complete the circuit, kick on the fan and operate as it should. and honestly i dont really see the need for a replay the way i would do it.
 

transparentdsm

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Jul 27, 2011
Messages
3,690
Location
Cherry Hill, NJ
to run a relay you need it to be set up like this. and if you want two fans you add another fan and another relay and splice into the first relay for your signals(temp sensor and ignition key).
 
Last edited:

tektic

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Joined
Dec 19, 2012
Messages
1,497
Location
ronkonkoma, ny
Thank you. The factor sensor has two wires. I fed one side ignition power. Other side goes to the relay. Other side of relay is grounded.

The problem is the fan goes on as soon as I turn key to on. I though it was a bad sensor, but now I'm assuming its going to shut off when the sensor gets to temp.

I just noticed there's two different sensors with the same plug but different threads. I'm using the ones that fit in the thermostat housing. That's the ac fan switch?

What I really need to know is if that's a temp sensor or a thermal switch. If its a temp sensor its useless in this app. If it is a switch I should only need to swap the output to fan to pin 87a from 87 to reverse logic of the circuit.

I'm pretty sure this will turn the fan on when the sensor is unplugged, off when plugged in and cold, and on when hot.
 

ktmrider

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Joined
Sep 10, 2007
Messages
3,128
Location
Tempe, AZ
The one in the top of the thermo housing ( pointing to the hood/sky ) is a Normally Closed switch. Was for the factory AC, shut off power to the AC if the coolant was overheating.

One facing to the firewall is Normally Open. This is also for factory AC, turns on the second ( DS ) cooling fan when AC is engaged.

Primary radiator cooling fan sensor is in the bottom of the radiator. Normally Open type.
 

tektic

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Joined
Dec 19, 2012
Messages
1,497
Location
ronkonkoma, ny
Thank you!

So I have to repin the relay. However that's going to leave the fan on when the car is in acc not on position... This sucks.

I guess I'm going to have to find a 3/8 bspt sensor normally closed. Booo
 
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