So I have a 98 sportsman 500 4x4 and the fan is not cycling on so I replaced the fan switch at the top of the radiator. It is pushing water as I can see it coming in thru the top of the radiator and I pulled out the thermostat ????? I can connect the two wire across the fan switch and the fan comes on???? Could the brand new switch be bad?

 

Are you leaving the radiator cap off and letting the engine get hot enough to trigger the fan? Plus is the hot light coming on? The sensor on these models send the voltage to the fan motor when it triggers the switch somewhere around 180 degrees.

 

The hot light does come on and with the cap on fan never triggers

 

I guess you've jacked the machine up to bleed all the trapped air out of the system and the radiator is clean. Plus if both hoses are firm and hot,then possibly you may have a faulty radiator sensor or possible it's designed to kick on at a hotter than normal temperature if it's an aftermarket one and the hot light triggers first. Plus on these model you must have enough coolant to cover the sensor or you can burn one up. This was the main reason the later models had the sensor at the bottom of the radiator.

 

Hmm more investigation needed I get in need to test that sensor in some boiling water and probably flush the radiator

 

Does the sensor in the head play any role in a 98 besides light the switch

 

Just triggers the hot light on this model.While you're at it throw the thermostat in boiling water also. You can tell if it opens or not.

 

Done already it doesn't open very much so I left it out for now what king of result should I get if I submerge the switch?

 

Resistance check on the sensor when cold. When warm resistance should drop. When it reaches a certain temp (usually 175-180 degrees) the switch closes allowing voltage to jump to the other wire that leads to the fan. Shouldn't be a ground problem as you said you can jump the two connectors and the fan kicks on.

 

Thx I will let you know what I find