Right you lot! I'm in need of some techy guru stuff and need yer help lads!

I've got a 88 (89 regd) F-J ... and the radiator fan is refusing to switch on to cool my baby down ... If you keep moving, then all is well .... but a couple of minutes in traffic sends her temperature way too high!

Is this a common problem? Is there an easy fix?

I'm handy wiv a spanner ... so has anyone got any suggestions? .... I'm not sure if its the fan thats bolloxed or a switch :S If its the fan, can it be replaced easily?

Give me a clue Lads Summer's coming and I dont want my girl frazzled

 

You can install a little manual switch for the fan. Just flip it on...
It is a pretty common problem, actually. Seen it several times.

 

Bodge up a couple of wires with a fuse (and a switch to avoid sparking) straight to the fan and connect to your battery. This will at least rule out the fan. Put a volt meter on the wires to the fan, run her in the shed 'til you know the fan should be on and look for voltage. I haven't checked but the fan must have it's own fuse...blown, dodgy contact in the holder or on the connectors somewhere?

 

It's probably a bad connection - the fan switch generally won't go bad - It could be a thermostat but also unlikely (under the right side front panel by the radiator filler)
Fit a separate switch and you should be good to go.


Good idea to check that nothing's caught up in your fan first - ya know, those girls nickers you couldn't find after the last ride......................

 

Yeah I'd go with the manual switch, mine heats up pretty good and fast when in traffic
in the summertime. Change the coolant and add some water wetter type additives , helps with heat transfer.

 

If you're not living in a country where the temperature gets up above 30C very often I'd think twice about the coolant additives.
I've been running some tests on my rad just lately with a digital thermometer sensor glued to the top rear corner of the rad.
The variation in temps between running and standing is amazing.
Currently in the UK the ambient is between 5 and 10 Celsius.
Starting the engine from cold the temperature will reach about 30 degrees within a few minutes of choke and gentle riding, assuming you're not launching straight down the motorway. If you keep moving at speeds of between say 30 to 60 MPH the temp will hover around 25 to 30 C. Push up faster and the temps will drop dramatically. I've been doing 120 MPH and registered only 12C on the gauge. That's stupidly cool!!!!
Coming to a standstill from a good run will see the temperature shooting upwards very quickly past 75C at which time the fan should have kicked in. Once it's buzzing away the temperature will remain at anything between 65 and 75C if you just let it idle. I haven't seen any temperatures higher than this so far.
My cooling system is working normally and the coolant is brand new, so is the coolant cap which keeps all the pressure where it's supposed to be.
As for your fan not working, that's bad news.
I'd be more interested in finding out if the temperature sender is working properly rather than fitting a manual switch. If it were me I'd probably not see that the gauge was trying to bend the needle into the red zone before it was too late.
Take your sender out of the radiator and connect an ohm meter across it. At room temperature you should have high resistance.
Drop it into a cup of water above 80C and you should see the ohms falling to almost nothing. If it's not doing this then it's faulty and you should just replace it.
Check the fuse under the L/H top fairing cover (which is clearly labeled on the underside of the cover) and if all looks good there then check you have voltage at the fan when the ignition is turned on. The fan actually has it's own pair of contacts on the ignition switch so if all else fails, the fan shouldn't.
Hope that helps you find the problem.
I'd be interested to hear anyone else's results from hotter climbs if anyone been as much of an anorak geek as I have.
If this didn't help, sorry to have bored you.
One of the reasons for my little experiment with the thermometer is that I am concerned about the amount of ram air through the rad. I think they over cool and loose performance and efficiency as a result. I have a plan which may transpire in time to come....... watch this space.

 

Hey Shakey,
I think Henry has covered most things but have you checked that you haven't got an airlock? Two reasons why i ask is that your temp seems to go up very quickly considering our not so hot British weather, and you mentioned that the fluid in the rad has been changed recently. You've still probably got a fan switch problem but your eratic temp gauge sounds fishy to me I've been riding my CBR1000 over the last couple of months and been nowhere near the fan coming on.

Gaz

 

Thanks lads .... you've given me some good stuff to go on .... I'll be testing things over the next few days .... I'll let you know the outcome Thanks again

I did a 90 mile run the other week and the old girl was fine ... no temp problems at all ... it's just when she stands in traffic, the fan just doesnt come on at all

 

If the temp gauge is messing you around, there's a red multi plug under the right side fairing, which sometimes gets loose and can stop the gauge. Mine has done it a couple of times, esp after working on the gauge cluster.
I hope it's that simple.................