Radiator Fan not working VFR750F 86'

[hkmac]

Hi All.

Got a question for ya.

Just got a 1986 VFR750F. The Radiator Fan does not appear to be working.

I followed the wiring diagram (to the best of my limited ability) and found an unplugged lead attached to the top of the tank.



This lead had next to it a lead to connect to it....



And when i connected to two .... the fan came on... and stayed on... non-stop... going full bore....

My first thought was that the temp reader to turn the fan off and on was faulty... but cant find that anywhere... (as I said... limited ability)

Then i saw the electrical point on the corner of the radiator itself....



and now I'm real confused as it looks like that's where this loose wire is supposed to go... but plugging it in seems to do nothing... even with the engine running hot.....

Anyone able to shed some light on this?

Cheers in advance..

[masonv45]

The Fanstat closes the ground loop - which causes the fans to run.

If your fanstat is bad, or you want to turn it on manually, all you have to do is short the fanstat to ground - which is what wiring the fanstat directly to ground did.

My guess is the PO had a switch hooked up where the wire comes off the tank. This way he could turn on the fan manually.

Many riders did this when their bike stopped cooling as well as it should have. This just masks the issue of a dirty radiator or a bad fanstat. The stock cooling system does just fine when it is in good working condition.

Test the fanstat and if it passes, see how quickly the bike heats up and causes the fans to come on. If it is too soon, then your radiator probably needs to be "boiled out". Most radiator shops will do this for $30-$40.

[hkmac]

Thanks mason...

That answers it exactly... for the life of me... I couldn't figure it out...

Cheers...

Love the avatar BTW..

[Army86VFR750]

About where on the gauge should the fan come on? The previous owner said the steam from the radiator would burn his leg and short out the electronics in heavy stop-n-go to no-go traffic. To me, that seems too hot!

Today it was about halfway through the gauge and no fan. I never had it hot enough to make steam, but never sat in too much traffic either.

Thanks!

[squirrelman]

You need to keep a close watch on the coolant level, making sure system is full. start the bike with radiator cap off and run for about 45 seconds to eliminate air from cooling system, then turn off engine, and add any additional coolant, and replace cap.

The fan should kick in when you reach about 2/3 to 4/5 of the range to Red Zone.

(Fan will not start below half-scale.)

The manual switch costs less than $5, while the Honda thermoswitch sells for over $50 and is known to be failure-prone. So guess which i recommend after my 18 years of VFR ownership....?????

[masonv45]

Fix it right: CoolingSystem - SabMagFAQ

Replacement fanstat from $14.99 and up.

The steam coming out of the radiator means that the radiator cap's pressure was too low or the bike overheated...probably because the fanstat failed and the fans didn't come on.