What feeds the fan switch relay with power?

P

philanthropy74

Registered
I have a 2000 Hayabusa. I have just had to replace the oil pan (long story, don't ask). When I have fired it up, she runs and she warms up but begins to over heat and will turn off when too hot. I put a 12v to the fans, they work. I checked the fuse for the fan, it was blown so I put a new fuse in and that now has power passing through it. The relay has no power though. When I put a 12v feed to pins C & D, A and B will make and break.....it clicks nicely so the relay IS working but there is no power getting to the relay even though the fuse is in and has power passing through it. When I clip the fan back to the harness, it is on permanently. What feeds power to the relay please?
 
philanthropy74 said:
I have a 2000 Hayabusa. I have just had to replace the oil pan (long story, don't ask). When I have fired it up, she runs and she warms up but begins to over heat and will turn off when too hot. I put a 12v to the fans, they work. I checked the fuse for the fan, it was blown so I put a new fuse in and that now has power passing through it. The relay has no power though. When I put a 12v feed to pins C & D, A and B will make and break.....it clicks nicely so the relay IS working but there is no power getting to the relay even though the fuse is in and has power passing through it. When I clip the fan back to the harness, it is on permanently. What feeds power to the relay please?
Click to expand...
IDK squat but I'll take a chance. The temp sensor has to give the go signal to the relay. If its stuck in the closed position...
Are you testing with yer motor hot? If you are,with the key in run position the fan will run till the temp sensor tells it to shut down,motor running or not.That is normal. Key on,motor cool,fan runs,you have an' issue.
Rubb.
 
I've ordered a new temp sensor but when the bike has cooled down, the fan is still on permanently when its connected and no power to the relay still.
 
It runs with or without the temp sensor connected and when I short the temp switch at the radiator, I hear the relay clicking. The fan is on all the time. It's as if the live feed for the relay is feeding the fans instead. I don't see any wiring issues where someone has overridden the switch or the relay but if this WAS whats happened, where is the most likely place it would have been done?
 
Kiwi Rider said:
Your 2000 model Busa has a thermo switch mounted in the left side tank of the radiator, not to be confused with the “coolant temp SENSOR” which is mounted on the back of the cylinder block.
Test the thermoswitch, I’ll put money on it being the cause of the fault.
Click to expand...
I'm liking this suggestion. Forgive my ignorance here but how do I test it? I have a vom meter, a power probe and a hammer?
Where is a good place to find spaces for the busa? eBay seems sparce....
 
Kiwi Rider said:
Your 2000 model Busa has a thermo switch mounted in the left side tank of the radiator, not to be confused with the “coolant temp SENSOR” which is mounted on the back of the cylinder block.
Test the thermoswitch, I’ll put money on it being the cause of the fault.
Click to expand...
Also, does this address the lacking power to the relay?
 
The thermo switch in the radiator switches power (sends 12v) to the cooling fan RELAY when the temp exceeds 220degF and then cuts the power to the relay when the temp reduces to 212degF
The relay supplies the current to the cooling fan when it (relay) is enegized by the power coming from the thermoswitch and relay cuts power to the fan when thermoswitch cuts power to the relay.
Below is how to test the relay and thermoswitch
Here's a quick way to test if the thermoswitch is at fault . . .
Unplug the thermo switch connector from the radiator.
Did the fan stop?
If so, put a paperclip between the connectors on the plug, does the fan start?
Here's a link that may just help you to understand the circuit . . .
www.hayabusa.org

Cooling fan won't turn on | Busa problems

I got back from a ride and watched my temp go into the red. I checked and know that the fan wasn't coming on. My first guess is the thermo-switch that turns the fan on went bad. Un fortunately, I need a multi-meter which I don't have to test it,
www.hayabusa.org www.hayabusa.org

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Kiwi, best answer yet. So the feed to the relay comes from the thermo switch. Got it. Makes sense. I have already tested the relay and it works.
 
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Kiwi, I've just checked the wiring on the thermo switch. When its plugged in, the fan is on 24/7... hot or cold. When I bridge the loom, nothing happens. No relay click and no fan turning on or off... the fan still runs permanently. Literally no change from the fans running continuously still. What should happen?
 
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Kiwi, I've just tested the thermo switch for continuity in situ on the bike. I don't have continuity. So the switch is open/not making the circuit but the fan connector has a permenant live feed to it dropping down from the fusebox part of the loom. When I take the fuse out and put it back in, the fan starts and stops... is this right?
 
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I think it might be the thermostat. I've ordered a new one just because its cheap and an easy swap but if the bike doesn't think its getting hot, this would explain why the fans aren't coming on
 
philanthropy74 said:
I think it might be the thermostat. I've ordered a new one just because its cheap and an easy swap but if the bike doesn't think its getting hot, this would explain why the fans aren't coming on
Click to expand...
That's unwise. It's best to figure out a problem before replacing parts which may not be bad. The thermostat doesn't send a signal to anything, it just opens at a specific temperature.
 
Mr Brown said:
That's unwise. It's best to figure out a problem before replacing parts which may not be bad. The thermostat doesn't send a signal to anything, it just opens at a specific temperature.
Click to expand...

But given its cost, if its staying shut, the bike wont think its hot because until the thermostat opens, the volume of coolant going round is small right?
 
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