My MC-13-250 has problems

[bandito2]

Oh, also that plug on the radiator is either a temperature sender or the temperature sensing switch for the radiator fan. When you first just turn on the key with a cold engine, does the fan come on? If it does then the PO rigged it up that way because the temperature sensing switch is bad or the wires on the connector to it broke off and it was easier to just patch the wires together for full time fan operation. Or the connector itself broke or any number of other things that caused non-operation. Normally your fan should be off unless the coolant gets hot enough to activate the fan switch.

If the fan is running all the time then check the wires to the fan; I'd bet you find some wires twisted together and taped. If he went all out with his remedy then he may have used a crimp connector here and there. But the fan will eventually wear out if it runs ALL the time.

You say your temperature was pegged? Check that when the engine is cold. If it is pegged when the engine is cold then that is another thing you'll need to correct. If not, then if you take another look at the the radiator, you may notice another one of those plugs in the radiator (or somewhere between the radiator and the engine) but with wires that are connected to it. That would be the temperature sender for the gauge and the one without wires to it is the temperature sensing switch for the fan. Or maybe he has swapped the temperature sensing switch wires for the fan switch wires and then (I think) the temp gauge would read either stone cold or pegged hot with no readings given in between because the fan switch is either off or on and the temperature sender has gradual electrical resistance depending on the coolant temperature. That resistance is converted into a graduated display of temperature on the gauge.

I don't really know anything about the particular manufacture brand of your scoot so I can't be specific about where things are or what they look like.
But those temperature senders and temperature activated switches are pretty basic to water cooled engines.
HTH

[bandito2]

One more thing; the radiator does not need electrical power to work. It is passive. It works simply by having coolant pass through it so it can transfer the heat away. It does that by air passing by the tubing with cooling vanes on it in the radiator. The engine provides the power to the water/coolant pump that pushes the coolant around the engine to pick up the heat and then through the radiator to cool it and then back through the engine again. It's a continuous cycle.

If your water pump stops working, or the thermostat stays stuck closed then the coolant mostly just sits there and gathers more heat until it is too much. (then bad things can start to happen to the engine ) Actually a thermostat will stay closed and keep the coolant from flowing around until coolant heats up to operating temperature, then the thermostat opens and lets the coolant flow normally around the whole cooling system.

I hope you guys don't mind me going on and on like this but it seems some are just learning about how their machines work. Understanding how they work makes things less of a mystery and empowers them to fix things themselves. (or at least helps with knowing just what the hell is going on with their bike.)