My 04 Grizz has suddenly decided to run the rad fan constantly on a 30 second on, 30 sec off schedule
Rad is clean, it's not overheating??
Could the fan switch be bad?
Water pump getting weak?
Any way to test these??

Thanks

pull the hood and check your rad coolant level

You can test the thermostat! Id check that 2nd after the fluid level!

Fluid is full.
How would a thermostat cause the fan to run every 30 seconds?

Not opening up, causing it to get hot, and run hot! Happens on sport quads alot. Thats what tell the fan to come on, when it gets hot also.

The fan switch on the Grizz is on the bottom left side of the rad, so rad has to get hot in order to turn on the fan. If the thermo is not opening then the motor would get hot but not the rad. The heat light switch is on the motor so if the motor was getting hot the light would come on.
At least to my line of thinkin!

The water pump pushs the fluid into the rad. and the threm. open to let cool fluid from the rad. into the motor. What are you using for fluid? You have to fluid out your old fluid if you use engine ice, or it will gel! around the water pump. One check the fluid level, and also for bubles in the motor. You can work them out. then check all the switch that control any of the fluids.Then look at the water pump, their not bad to rebuild if you have a manual.

I think you had better check, it seems you have your order backwards!
The water pump pushes water thru the thermostat into the top of the rad, cool water can't enter the motor till the thermo opens, so if it's stuck closed the motor gets hot but the rad doesn't. Seems to me if the thermostat stuck open the motor should have a hard time getting up to temperature so the fan shouldn't run at all.
How does air bubbles get into the system if it's never been opened?

Has anybody ever had a water pump go bad on a Grizz??

Just curious if you cleaning the front and back of your rad? So many people think their rad is clean when it really isn't. Make sure you get right in behind the rad and rinse it well, the mud can get caught up in the corners and be baked right in there! Use a garden hose and a shower setting setting and spray both the front and back until you see clean water draining from. Don't use a pressure washer, it can bend the fins and then it won't matter how clean it is, it just won't cool enough. Good luck.........Irv

I have a little rig that mixes water with air pressure. It works very well is not so "abusive" as a pressure washer! It's easy to blow any dirt right out with water from the back, it's also easy to see the water flowing thru the vanes easily.