Hey all,
The cooling fan on my '87 cane has never worked properly since the day I bought it. The problem has something to do with the thermostatic switch, because when I ground the wire going to the fan, everything works fine.

Thinking the switch was my problem, I bought a new one and installed it. Same problem. The kicker is that I don't know if the bike is actually getting hot enough to trigger the switch because I recently installed an aftermarket coolant temp sensor.

I placed the sensor in the upper radiator hose (the one connected to the upper right side of the radiator). My clymer manual says that the fan should kick on somewhere between 208 and 216 so I let the bike warm up to 220*F. The fan didn't budge so I shut the bike down in fear that it was getting too warm.

So I guess my question is, would the coolant be that much warmer near the fill cap than it is in the radiator? Can I let the bike warm up to 230 or 240 to see if it trips the sensor?

I guess I could move the sensor to the lower radiator hose since it's closer to the sensor, but that would mean buying some new hoses...Just thinking out loud here.

What are your thoughts? This is driving me nuts!

 

Check the cooling fan fuse.

Also, check all of the connections for the cooling fan making sure they are tight.

Your fan has nothing to do with your coolant temp sensor. There is a separate fan switch screwed into the left lower portion of your radiator. Get yourself a multimeter or test light. Unplug the connector from the fan switch and set the multimeter to the DC Volts or test light. Connect whichever testing mechanism you have to the positive battery terminal and the alternate end to the fan switch(where you unpluged the wire from) When the bike is cool, there should be 0 V or the test light should be off. When the bike is warm, there should be current. So let the bike idle until it gets hot, as in your temperature gauge is almost MAX and retest, there should be voltage now, or if using a test light, it should be on. (This test confirms your cooling fan switch works).

Last but not least, if everything else checks out fine, you will need to remove your radiator and take the cooling fan apart (Extremely simple to do) There are 3 screws on the back of the cooling fan motor, take those out and it comes apart. With it apart, look at the 2 brushes inside that make contact with the stator portion of the fan. Look for corrosion and that they move in and out freely, as well as arnt worn down too far that they dont make contact anymore. If this does end up being your problem, a auto electric shop (rebuilds starters and alternators) can fix this for you for about 20 bucks.


Hope this helps.

 

tds94probe, thanks for the reply but I don't think you read my whole post.

I know the fuse and all the wiring is good because when I ground the fan switch wire the fan works fine. The radiator is also grounded properly so there is no reason the fan should not work. The LAST possible thing that could be wrong is the fan switch itself, but I just bought a brand new one from the dealer.

What are the chances that the fan switch I bought was broken when I got it?

Thinking that maybe the coolant wasn't getting hot enough I let the bike idle until my aftermarket digital temp gauge read 235*F. The fan still wouldn't turn on and there was cooland spewing everywhere. I also thought that maybe there was a giant air buble in the system and the fan switch wasn't submerged in coolant. I filled the system to the brim, burped it, leaned the bike over and everything elso I could think of to remove air bubbles. Still didn't help.

So what now? Go back to the dealer and demand that they give me a new fan switch? I doubt they'll go for that but you never know. I am so sick of this bike right now...

 

Check your radiator mounts for corrosion, clean them up so they make good connection to the frame.

 

When I string a voltage meter between the radiator and the positive battery post I get 12.9v. But I will take the radiator off and have a look. Thanks.

 

Hi, did you ever sort this out? I have the exact same problem and its driving me nuts.

 

Sorry, I haven't had much time to mess with it. One of these days I'll pull the switch and test it to find out if that's the actual problem. I'll let you know how it goes.

 

My friend just puchased a 1988 CBR600f and the fan comes on with ignition.

I'm assuming one of the previous owners had the same problem as the OP and just wired the fan straight to ignition.