Bikes, Hints'n'Tips > Fazer 1000/FZ1 corner

Help Please - Cooling Fan Not Working

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Falcon 269:
As anyone who knows me knows, I hate troubleshooting electrical problems, so I'm appealing for help. :)  I’ve already hit the Search function which helped me with steps to investigate but a solution has eluded me so far.

Bike is a 2002 Gen 1, 53k miles.  Yesterday I started her up just to circulate fluids and make sure all was well before advertising her for sale.  Last time ridden was a couple of weeks ago and all was fine then.

On start-up, I’m 99% sure that the coolant fan came on as it usually does soon after starting.  Went off with gear selection and I then proceeded to hold the revs around 3k rpm and blip the throttle to get the motor up to temperature.  Usually when I do this I let the coolant get to around 90C and then turn off but this time I decided to let her run to check that the fan came on when the temp reached 98 - 99C.  It didn’t.  The Multigauge coolant temp continued to climb to 104C at which point the coolant overheat light came on - as it should - and I shut her down.

Today I started troubleshooting by applying 12v direct to the fan.  It works fine.

The fan fuse is good.

Applying 12v to the relay contacts I got a ‘click’ suggesting it’s working correctly.  I also substituted another relay and that made no difference to the fan operation. I’m calling the relay itself good.

Earthing the green/black terminal on the relay connector turned the fan on, suggesting the wiring from relay to the fan is OK. 

The temperature readings on the Multigauge were exactly as they’ve been since I fitted the gauge.  Coolant temp rose normally and the overtemp light came on as it should at an indicated 104C.  This suggests that the coolant temp sensor in the thermostat housing is also good.

The coolant overtemp light comes on briefly at ignition on as it should.

However, the fan no longer comes on soon after start with the revs held at 1500rpm plus and the coolant fan does not kick in when the temp reaches 98 - 98C.

I’m stumped at the moment and the only thing I haven’t checked yet is the combination unit in the speedo which should be activating the fan relay when the temp gets too high.  I believe it also has a timer function to run the fan at start-up.

Any ideas, experiences, hail Mary guesstimates would be much appreciated. :)


Hi Mike,
as you've ruled out all other potential fails, I suspect it's the control circuit inside the cockpit. I've detected and reapired such a defect a while ago. Maybe it's the same in your unit.

The picture shows the affected part of the pcb. Most likely transistor TR34 is not working. Ignore the red coloured parts, that's from another, older discussion about manually activating the fan.
According to the marking code (DF) it's a standard NPN transistor, maybe 2SC2463-F (55V, 100mA) (those markings are not clear without ambiguity). Any similar type should also do fine. Also replacing with a wired (non-SMD) type will work. I know, it's not an easy job..
For testing you could replace the temperature sensor by a wired resistor of less than 1700 ohm. That equals ~105°C. The voltage at anode of D32 should drop from 12V down to ~1.5V, the collector of TR34 accordingly (fan relay or equivalent load must be attached).

Hope that helps.

old son:
Still sounds bloody complicated to me!!!

Falcon 269:
Hi Christian,

Many thanks for replying so quickly.  I posted on the FZ1OA as well and grommet there was equally quick off the mark.  He also mentioned you might be the man to have a chat with about this. :)

You both seem to conclude that the problem is most likely on the control board in the instrument cluster.  I'll have a look inside tomorrow for obvious physical signs of failure but testing components isn't one of my talents.  I could probably replace an SMD, though, provided I can get the correct component.

Please excuse my ignorance but could you simplify the process you mentioned for testing by replacing the temp sensor with a wired resistor?  Where would I put the resistor in the circuit and how best to achieve this?  If it can be hit with a hammer, I'm good to go but anything involving wiggly amps and squiggly volts melts my brain cell. :)



Falcon 269:

--- Quote from: old son on 02 March 2020, 07:56:44 PM ---Still sounds bloody complicated to me!!!

--- End quote ---

Damn right, mate. :)

At least you don't have to try and wrap your head around it like I do, though.  :rollin


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