Sanity check - electric radiator fan switch - Defender Source
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  #1  
Old June 26th, 2013, 05:42 PM
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Sanity check - electric radiator fan switch

Switch should be off, no continuity, when cold right?
Then when temp gets up high, switch triggers, continuity, which turns fan on, right?
I got two new switches in a row that both had continuity between the contacts out of the box, at room temp...

Do I just have bad luck or am I losing me mind?
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  #2  
Old June 26th, 2013, 05:53 PM
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check the body of the switches they may have "NO" - normally open - what you should have or "NC" - normally closed - what you appear to have.

heat switch in pan of water does it go open cct when hot ? if so this type of switch need a relay to work correctly.

regards

Gren
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Old June 26th, 2013, 06:06 PM
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John B.
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What switch are you buying?
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Old June 26th, 2013, 06:17 PM
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The power goes first to the fan, then to the temperature activated switch which grounds it to the engine block, creating a circuit whcich allows the fan to operate.
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Old June 26th, 2013, 06:45 PM
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more info

The switch is a prc3359, made by Facet.
My previous setup had power to the temp activated switch, (not prc3359), which would go to the fan then to ground. I deduced the old switch didn't work since the fan never came on and I tested it with a lighter and nothing.
Fast forward to today... I tested the new switch as Gren suggested but used a lighter and ran it out of gas. I then used a propane torch and once it got up to temp the new switch closed, opposite of what I expected.
I then put the torch to the old switch and once it got to temp it came on! I guess the lighter wasn't hot enough. I guess the engine just never ran hot enough before.
Still not sure why the prc3359 would be on when cold, off when hot. I suppose I'll just go back to the old setup.
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Old June 26th, 2013, 07:52 PM
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You have the wrong switch. It is meant to disable the A/C during an overheat... So it is NC. You want PRC3505.

http://forums.lr4x4.com/index.php?showtopic=37904
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Old June 27th, 2013, 02:13 AM
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You're right, John, nice find. Thanks for steering me straight.
I think I will wire it differently than it was originally and take Bill's input and run power to the fan and the ground through the switch.
Thanks everyone!
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Old June 27th, 2013, 10:19 AM
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I just looked up that switch that John mentioned. It is a two-terminal switch which means that power does indeed flow thru it. It does not go ground. Don't reroute the circuit.
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  #9  
Old June 27th, 2013, 03:04 PM
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I needed to know that for a future AC intallation.

Does anyone know of the when the fan clutch open and close on the disco 300?

Gage problem what could cause it to read hot all the time?
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