Modern Vespa

I've noticed lately that when starting the engine, even when the temperature is right at freezing, the cooling fan runs wide open. Turn the key hear the whine.

Before I go buy a temp switch (temp sending unit)part 584676; I would just like to run this by you guys to see if this is indeed the cause. Or could this possibly be some other issue.

Thanks in advance.

I would test the temperature switch with a meter before I bought another one. If the switch is closed when the engine is cold, there's the problem. Switch is bad.

Good idea testing that thing.

Also wonder if it could be the coolant temperature sensor part#82622R sending the wrong info.

Could also be bad connection. Just went thru this on a GTS 250. Search postings

Unplug temp sensor and see if fan still runs. That could eliminate a bad fan relay

If like the GTS 250 there are 2 sensors in that one element. One goes to the dash indication the other to ECU to control fan. If you measure the resistance of each sensor they should be the same

My bets are on the switch. The temp sensor would be sending the temperature to the ECU (and the temperature gauge if the GT200 has one), but I don't think it directly controls the fan.

Yes this model has an analog temp gauge on the dash. It runs cool and has never overheated and after setting a few months noticed that fan coming on when the ignition key is turned on with a very audible whine.

a quick check is to pull the temp sensor connection and see if the fan stops. I would also check the resistance on the sensor.

more likely is that the fan switch has failed, or less likely the fan relay itself.

but I'd check for any loose wires first before buying parts.

Thanks Greasy....good idea.

The temp sensor on the GT200 is nothing to do with the fan - the fan is purely controlled by the thermal switch inline with the hoses - or on the LH radiator, I forget which.

One side of the fan is permanently at +12V, the other goes to ground via the thermal switch.

Thanks for that heads up.
Noticed in the parts diagram that the sensor did look like it was inline with the radiator hose. Well I bit the bullet and ordered both from ScooterWest just to be on the safe side and my luck when torn down it'll be a loose wire. The ole girl has held up fairly good and usually it's a lose connection or a hose that went bad losing suction or some such.

One thing I don't understand is the fact that the fan only runs when the ignition is on - or is it when the engine is running? On the GT200, the fan 12V feed is on permanently, and if the bike overheats the fan will stay running with the engine turned off, until it's cooled down. Perhaps someone has added a relay or somesuch?

thanks for the correction Jim, I was having a moment there.

thermal switch is inline with the hoses on the RH side just below the radiator.

Everything runs normally there is no overheating. The fan runs constantly the moment the bike is switched on, starting, and while running under normal loads.

As we all know the fan kicks in when it hits a thermal setting to keep cool, but this was a new one, hearing that whine while starting or even switching it on to start the start process even when the temp is below 32 degrees and has been sitting and cold as a witches titty. Even here in the deep South...brrr.

Found out the reason for the fan auto on AND the headlights were intermittently going off and on was, after taking the assembly apart to change headlight bulb, noticed a red multi-wire connector on the back side of the speedo/dash, was not quite 'snapped' in properly. Pushed that in and changed the LED bulb while I was there and everything went back to working properly.

So all the folks saying check for loose wires (and or connections) was spot on.