Hi all,

i have got a gas gas 321 2001 with rectifier/fan issues, i get ~10v ac from the voltage regulator, then at the rectifier when input the multimeter on the red and black wires to and from the fan (with the fan disconnected) i get ~25 to 30 volts, which is going to cook the fan pretty quick, when i earth the black wire i get ~ 10 to 12 volts, not sure what is happening there if anyone has had similar issues ? And could help please 

 

Thanks Anth

Multi-meter sucks for reading AC an oscilloscope is the way to go, that said it sure does sound like you have the multi-meter on the wrong settings.  Start with the stator output, that is where you should see lots of non-regulated non-rectified dirty voltage coming out, your lights originally use non rectified power with the AC voltage controlled only by a regulator that sends excess voltage to ground (make sure the ground connection is solid and if that is not happening your regulator is fried.)  your fan motor is the only thing requiring DC volts so after the thermostat switch you have the full wave bridge rectifier.  That rectifier contains 4 diodes and is the part that will most likely fry if your voltage regulation fails.

If voltage output from the stator gives wild numbers inspect the stator coil for damage from heat and test the continuity on the coil windings.  From the yellow wire output to ground should read 0.1 to 0.2 ohms as per the GasGas wiring schematic.

That was my first trials bike.  I have attached Jim Snell's wiring diagram.  Pretty sure I had to replace the thermo-switch at some point.  Best way to test the fan is by connecting it to a 12-volt battery.  The regulator (Transval) is probably a Zener diode clipper.  Remember that any voltage you measure without its load (fan) will be somewhat higher than when it's loaded.  

The thing Snell calls the DC Converter is just a bridge rectifier.  Here's a YouTube on how to test it.

 

Simple Zener diode will be mounted on a heat sink and shielded from melting anything.  Time was when you could buy that fridge rectifier from a local radio shack store for 4 bucks, dating myself.

On 4/17/2024 at 3:19 PM, konrad said:

That was my first trials bike.  I have attached Jim Snell's wiring diagram.  Pretty sure I had to replace the thermo-switch at some point.  Best way to test the fan is by connecting it to a 12-volt battery.  The regulator (Transval) is probably a Zener diode clipper.  Remember that any voltage you measure without its load (fan) will be somewhat higher than when it's loaded.  

The thing Snell calls the DC Converter is just a bridge rectifier.  Here's a YouTube on how to test it.

 

Thanks, im not sure which terrminals refer to which on the youtube video though, and how that translates to the rectifier 🤣🤣 i’m not so great with electrics, engines yes 

Yellow wires are the wavy line.  Black is negative.  Red is positive.