Cooling Fan won't come on. The fuse is good and fluid level is good. What else could it be? {Paul, NH 1999 Honda Shadow Spirit 1100}
Answer
Check the fan itself. Can you spin the blade by hand? If so, move on to the next paragraph. If not, it may be jammed with debris or the fan motor may be seized. Try cleaning out any road debris you can see. If it still will not turn it is seized and most likely needs to be replaced.
There is also a thermal switch on the radiator. When the temperature gets high enough, this switch will send negative current to the fan. It is usually a large, brass with two wires going into it. Jump these two wires together on the bike side, with the key on, if the fan starts to spin, the thermal switch is bad.
If the fan does not come the thermal switch is ok. Your fan motor may be bad. The fan motor has two wires, one positive and one negative. Using jumper clips, supply positive to the positive wire & negative to the other, from your bike’s battery. If the fan starts to spin, the motor is good.
Both the thermal switch and the fan motor are not inexpensive items to replace. Check the online microfiche for part numbers.
In the above schematic the item number 5 is the Fan Motor Assembly part number 19030-MAA-023. Item number 34 is the Thermo Switch Assembly, part number 37760-MT2-003.
If the fan motor tests good, but it still will not function properly, please do not take the short cut that many shade tree mechanics with a cooling fan problem do, that is wiring the fan directly to the key switch.
When the fan is connected directly to the ignition switch it will run the entire time the bike is running. While this is ok to get you home once, it is not a long term fix. The fan running constantly puts stress on your battery, alternator and electrical system. This just sets you up for a breakdown.
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