Fans aren't working!!!

[sunspark4600]

My 91 SP seems to have decided it's fans aren't really needed for the whole cooling thing and because of which is now frequentley trying to boiling itself.
I've topped up the coolant but haven't been able to take it apart and check.
Since it was working ok a couple of weeks ago I have replaced the clocks (from MPH to KPH) however the temp gauge is working, the fairing has come off and been put back on and the chain and sprockets have been replaced so something may have been inadvertantly clobbered with my big rubber mallet o'death.
Anyone got any ideas or a rough idea where to start?
Cheers!

[rover220]

bridge the two wires that go to the sensor on the front of the rad.

this should force the fan on, if it doesnt you have a fan/wiring/fuse problem.

[zimm]

what he said,

plus, if the head-gaskets gone (and im not saying it has) the bike will "boil" and spit out coolant way before its actually anywhere near hot enough to switch the fan on as the cooling system gets pressurised.

[masterofinsanity]

does the fan come on when you indicate>?

[sunspark4600]

Cheers guys, I'll try the sensor and indicator thing tonight.
The gasket and cam chain were going to be replaced this winter however I may get it done soon if this is the case I have noticed the past month that the fans were kicking in quite quickly at lights and that it was a bit warm, what am I looking for to see if it's going? If it's simpler I can provide pics of any parts.

[rover220]

if youve been riding and its warm it wont take long sitting at the lights to bring the fan on. nothing to worry about imo.

[Vard66]

Was this resolved, anyone? I'm having similar issues. Just about hit the top end of the temperature gague while making my way through traffic in Swindon earlier.

[masterofinsanity]

vard have you bridged the wires to see if the fan comes on? make sure your knuckles are out of the way of the fan when you do this.

[Vard66]

I haven't, no. I'll try to find a moment or two to do this later on.

[steve87]

i have this problem too.. but i have tried the fan wiring, and the fan works, in my opinion on my bike, i think the thermostat has failed closed, as the radiator is warm, but not reallyhot, when it says the bike is, i have put new coolant in mine, so today, the thermo comes out to be tested to see if its opening..
when the head has gone, the oil should go like milky/ mayo, or the coolant shold turn yellowy shouldn't it?

[masterofinsanity]

when the head has gone, the oil should go like milky/ mayo, or the coolant shold turn yellowy shouldn't it?

in some cases yes but the head gasket can go between the water/exhaust side then the water will evaporate without you knowing, unless you check your coolant levels.

[Caakman400]

Funny, I had the same problem two days ago; noticed the fan didn't kick in when it should and the temp just kept on rising. Great bloody timing for the summer...

Anyway, fan still works, but the thermostat is shot so have ordered a new one.

I could actually hear the coolant bubbling at the red light the other day. Not good.

Which model bikes are you all running? I've got a 95...maybe the lifetime of the part is around 13years or summat?

[Vard66]

'94. I'll check the sensor too. Maybe we could do a group buy...

[steve87]

mines an 89 h1, but has not been used for a few yeas, will be fitting a new fan sensor tomorrow, so watch this space!!!!!

[deviant]

A few easy* checks you can do are:

1) Pull the connector off the fan switch (in the rad) and short across them. If the fan comes on it's the switch or the connector.

2) Check that there is 12V across the connector when it is unplugged from the fan switch.

3) Take the switch out of the rad, measure the resistance across it cold (should be infinite) and with the end dipped in boiling water (should be near enough zero). I've also done this with the switch in the rad and the rad off the bike by tipping a kettle full of water into the rad.

4) Find the connector where the fan plugs into the loom. Cold you should see 0V across it, hot (or with the fan switch shorted out) you should see the best part of 12V.

5) Apply 12V to the fan and see if it spins.

6) Get the thermostat out and check it opens in boiling water, as someone else suggested.


The GPZ has a more fundamental fan problem at the moment - the rim/blades of the fan rotor have actually separated from the hub bit which is fixed to the motor. So the middle spins but the outside doesn't. We discovered this on the way out of nottingham at the start of our holiday, and spent the next two weeks trying to avoid taking it into cities.

*easy if you have a multimeter. If you don't, invest in one for less than a tenner. I value mine that highly in tracing bike electrical problems that I carried it for 2700 miles round Europe - and used it twice.