Fan doesn't turn off - any ideas?

[daft1024]

Hi all,


My 99 fzs600 has developed a weird electrical gremlin that we can't seem to fix.  Sorry if this has been posted before. I tried a search but could find this described anywhere.


The fan turns on as usual when it gets hot, but it doesn't turn off. The thermo fan switch is near new - was replaced 2 years ago and it's been working fine turning on and off until around 2 months ago.


The bike doesn't seem to be overheating.


It's like there is a busted relay but I can't seem to find the relay that runs the fan. The wiring diagram doesn't seem to even show a relay on the fan but that doesn't make sense.


Has anyone had this before? I've tried 2 mechanics and an auto elec - but they can't seem to find the issue.


Does anyone know what relay runs the fan or had this issue before?


Thanks in advance!

[unfazed]

There is no relay on the fan circuit.Does the fan go off if you pull the Fan Fuse?Does the fan go off if you pull the connector off the Thermo fan switch?

[daft1024]

No relay! OK that makes sense why we couldn't find one. The auto elec was adamant that fans need one.


When the fuse is pulled it turns off but when the thermo switch is pulled off it still runs!


Does that make sense?


We changed the fuse but it didn't fix the issue. I didn't change the thermo switch as it's only 2 years old (and it doesn't help that there are none in the country).


Do you know it the engine temp thermo switch has anything to do with the fan. The wiring diagram doesn't see to show any interaction.

[limax2]

On a FZS600 is not normal for the fan to come on under normal riding conditions, usually only in slow traffic on a hot day or stood idling for a period. I have a temperature gauge on mine and it very rarely gets above 85C. The fan is only meant to come on round about 100C.
Your problem does seem strange because pulling the plug on the fan switch should break the circuit, so that suggests a short across the plug or the wires to the plug, however if that was the case the fan would come on as soon as the ignition is turned on even with the engine cold. The other thermo switch for the warning light (with a single wire) is on a separate circuit, although still on live when the ignition is on. Sorry I can offer more help, if I think of anything I'll return.

[daft1024]

Thanks for that -it is rather odd. I've had the bike since new and it's always been a cool runner.


I think your right that there must be some kind of break in the circuit. Damn hard to find though. I might try running a new wire and see if that fixes it.

[unfazed]

With the ignition off pull the thermostat connector and check for continuity between the blue and brown wires, if there is continuity here then there is a short circuit in the connector or somewhere between it and the fan connector.

[SamTomlin94]

Do you have a Haynes? I've got one for my fzs600 I can photograph the 'leccy plan/circuits if you need it ?

[BBROWN1664]

Do you have a Haynes? I've got one for my fzs600 I can photograph the 'leccy plan/circuits if you need it ?

Downloads section of this forum has the yamaha manuals in it.

[SamTomlin94]

[quote author=SamTomlin94 link=topic=27306.msg329134#msg329134 date=1652482131]
Do you have a Haynes? I've got one for my fzs600 I can photograph the 'leccy plan/circuits if you need it ?

Downloads section of this forum has the yamaha manuals in it.
[/quote]


:eek :eek :eek  it does?! Sorry I'm a new member here...are there any other treasure troves I should know about?!  :lol