Cooling System Theory: Thermostatic switch operation (fan control) if thermostat is stuck

[captainmurph]

I've managed to get this GL1000 running and now seem to have a cooling problem. The guage moves up quickly toward the redline and the fan didn't seem to come on.

I've bypassed the thermo switch (jumper across rubber cap connector terminals) and the fan runs just fine in this mode. Since it still overheats, I'm assuming that the thermostat is stuck closed.

If I look at the parts fiche, it looks like this thermo switch is located so it will sense the temp of coolant that has gone by the thermostat to the radiator. If that is the case, the switch might be good but never seeing coolant temp hot enough to close and turn on the fan.

Before I pop for nearly $70. for this swtich, can anyone confirm that my hunch is correct?

Of course, I can replace the thermostat and find out that way, but I'd have to drain the coolant again if I'm wrong.

Thanks.

 

[dan filipi]

I've managed to get this GL1000 running and now seem to have a cooling problem. The guage moves up quickly toward the redline and the fan didn't seem to come on.

I've bypassed the thermo switch (jumper across rubber cap connector terminals) and the fan runs just fine in this mode. Since it still overheats, I'm assuming that the thermostat is stuck closed.

If I look at the parts fiche, it looks like this thermo switch is located so it will sense the temp of coolant that has gone by the thermostat to the radiator. If that is the case, the switch might be good but never seeing coolant temp hot enough to close and turn on the fan.

Before I pop for nearly $70. for this swtich, can anyone confirm that my hunch is correct?

Of course, I can replace the thermostat and find out that way, but I'd have to drain the coolant again if I'm wrong.

Thanks.

I would start by removing the thermostat since you are right, if it's not opening> the temp sensor will not sense the hot coolant to turn on and it does sound like the T stat is not opening (if your gauge is reading correctly).
To sort this out, drain the coolant into a large enough pan then add plain tap water for testing. No need to use distilled water if only temporary.
Once the problem is solved drain the tap water and put the coolant mix back in.

 

[mcgovern61]

Pull the thermostat and test it in a pot of water. (Might not be a bad idea to just replace it if it is out.) Here is a video on how to test your fan switch:

viewtopic.php?p=28869#p28869

 

[slabghost]

How are you determining there is overheating? Gauge on the bike? Headers glowing?.Coolant boiling over? Does the fuel gauge read correctly?

 

[danf]

Fan Switch is bad..

 

[scdmarx]

Fan Switch is bad..

Gotcher crystal ball out of the shop already? :smilie_happy: :yahoo:

 

[danf]

Yahhhh crystal ball yahh :Egyptian:

 

[slabghost]

if it is still overheating with the fan running. I'd pull the thermostat and run without.

 

[danf]

I'm pretty sure he is saying he just tested the fan when he says he by-passed it, I don't think he is operating the fan via toogle switch because he didn't say that, my bike's temps. will run up hot too if the fan never stops it but the fan switch on mine has never failed me, Murph, your fan switch is more than likey as old as the motorbike, it would be wise to change it out regardless, even if it's not the problem , I think your troubles will stop if you get a new one..Now if I'm wrong and you are running the fan via toogle, then your thermostat probably is jacking with you and if Joe says to remove it and Dan said to, the, I would.. Autozone has a fan switch for the correct temps , part MT1373 special order, three or four days..$42 but you must either get a plug in for it or rig it up, pig tail style..Oh Murph you could just use a toogle switch to operate your fan too, I like it to operate on it's own though..