Hi....got an 06 SY250 with no fan. Fan works off a direct 12v battery feed but not from the bike's power supply. Wiring has been modified but looks okay and the ignition side is fine. Was thinking regulator for the fan but it looks like it has a rectifier and a capicitor in the circuit. Anyone know how to eliminate one or the other or which is most likely to be the culprit? Thanks in advance.

Edited February 13, 20215 yr by hoodie2

Check what is going on with a multi-meter.

The most common reason for the fan not running on a trials bike is the thermostatic switch not making/closing.

Thanks for the reply. I should have mentioned that bridging the thermostat wires makes no difference. The bike runs fine otherwise. What I'm wondering is do failures of the fan condenser and failures of the rectifier have different symptoms. I'm trying to eliminate one. The fan doesn't seem to activate at all. If it was just a condenser fault would I get the fan running intermittently?

Yes

Maybe

What did you find when you measured the voltage at the fan?

Edited February 14, 20215 yr by feetupfun

Output to the fan is 3v dc. That help?

 

Also only have a cheap multimeter so not able to measure the fan condenser capacitance. On a 2k ohm resistance setting though the condenser will charge to open circuit on either polarity. I think that tells me the capaciter is good so I'm leaning towards thinking the rectifier is not giving me enough voltage dc. That sound reasonable?

Edited February 14, 20215 yr by hoodie2

It is good to know that you are getting some voltage at the fan because it means that the stator coil is working.

Yes the DC voltage at the fan is too low.

I don't get what you're saying about the capacitor except that you think it s OK.

Okay thanks for the help. I'll replace the rectifier and see how I get on.

Replaced the rectifier and still only getting 3v dc and no fan. I'm now thinking the rectifier converts ac to dc but the condensor is whats boosting the voltage. Will have to try a known good condenser. Anyone know what value the fan capacitor should be? Might be able to test it at work with a better meter.

Swapped out the condenser and still no fan. Rechecked output from stator and was getting little or nothing. Checked the stator and found a clear break in the windings. Will swap out the stator and see if that sorts it. 

Just to round this off I changed the stator and that sorted it. Could have saved myself some time and money if I knew how to use a multimeter properly. Every day's a school day!