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Polaris 400 cooling system

2K views 8 replies 4 participants last post by  polman500 
#1 · (Edited)
So I am replacing the Head Gasket on my sons 400 Scrambler - Along with the fan sensor (cylinder head) and the radiator sensor (both were new old stock) - After everything is reassembled is there a way to check the fan operation ? Can one of the sensors be jumped to turn the fan on ?
 
#3 ·
Whatever you do don't heat the sensor with a flame - it can overheat it and cause it to fail. Unplug the sensor and short between the two wires with the key on to see if the fan runs. If the fan runs and you want to check the thermo switch operation, suspend the switch in a pan of water (do not let the thermo switch lay on the bottom of the pan) and heat the water with a torch - just as the water starts to boil the switch should operate and turn the fan on.

Don't worry about putting the wires in the water - it's only 12 volts DC and the water will not conduct the electricity - if you don't believe this, disconnect the wires from the thremo switch and immerse the switch wires into a cup or bowl of water with the key on - the fan will not run or might maybe turn very slowly if there is a high content of impurities are in the water.
 
#5 ·
Yeah - a flame will heat the thermo switch so rapidly it can permanently damage it - maybe not every time, but more often than not - for the cost of a thermo switch it's just safer to use hot water and not take a chance on damaging it.
 
#7 ·
Polman I am still waiting for the new Head Gasket and the 2 Sensors (head & Radiator) Dont want to put it all back together and wait for the fan to come on ,,,, I would rather test it and know that it has power . The Radiator sensor is discontinued and I think I found the last new one on the planet . Dont want to damage anything
 
#8 ·
LOL, Well the thing in the radiator, I guess you can call it a "sensor" is nothing more than a simple fan switch. When it gets to a certain temp it completes the circuit to make the fan switch on. When it drops back below a certain temp it breaks the circuit turning the fan off. That's all it does. You can get one at any auto parts store for a fraction the price Polaris wants for them. The same switch/sensor or whatever you want to call it is used in many small cars and trucks. They may have a different connector but that's easily changed.
They're also readily available on ebay for cheap brand new! Here's a link to one of several. Of course you can test the one you have in a pan of hot water if you like.

https://www.ebay.com/itm/Polaris-Sp...h=item2130559981:g:pa0AAOSwUn9Z6XBT:rk:2:pf:0
 
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