Cooling Fan

[Bill L]

On my 2018 Sector 250 the cooling fan has stopped working. The fan and thermostat switch both test good alone with fuses. There is no power to the thermostat switch. Feed wire is red with black stripe. Wire diagram is little help as it shows feed as another color. Where does the fan power come from? Ideas?  Thanks 

[T-boss 410]

Not sure if this will help, but I assume the power to the fan comes from the ignition switch. I say that because there's some members here that have wired the fan on their UTV to run constantly when the UTV is started. They do so with a short jumper wire on the temperature sensor wire plug at the radiator. With this in mind, I believe that the fan's power supply is from the ignition switch. Don't know how it's wired to supply the power to the fan, though. Maybe someone will chime in that has made this modification.

[Bill L]

It looks like the power comes from the ignition switch and goes to the fuse box and the to the fan switch. Wire diagram is not very useful. Looks like everything electrical (lights, horn, power port and more) are powered by the wire from the ignition switch. Seems like a large load for a small wire. 

[Pop Bob]

I had the same problem on my vector 500. I could not easily trace the power supply from the radiator sensor fan switch back to its origin. I wound installing whole new bus for accessory use in the glove compartment. I ran a fused #8 wire to a relay and trigger the relay on when the ignition switch is turned on. I then ran a fused wire to the sensor/fan switch. It works fine, no problems yet. I also installed an indicator light on the dash to show when the fan is running. I thought that was easier than tracing the harness plus I have no decent schematic. It also gave me a nice power point for adding other accessories like light bars and whip lights

[Bill L]

It looks like the power comes from the ignition switch and goes to the fuse box and the to the fan switch. Wire diagram is not very useful.

[Bill L]

Since the fan only draws about 3 amps I tapped into the dash power port that is fused. Fan works as it should but I would like to know what broke.

[T-boss 410]

Did you check the original wire dedicated for the fan coming from the fuse box to the fan? Just curious if it had power. Maybe an issue with the fuse box. 

There's no relay for the fan?

[Bill L]

Seems somewhere in the harness the fan feed wire changes color. Wire diagram shows no relay of even a fuse. Ignition switch feeds the fuse box that feeds the fan circuit off the fuse box. Problem could be in fuse box but hard to tell since my wire colors don't match my factory wire diagram colors.

[Ben1098]

Surprise answer.  The units are Yamaha Rhino clones.  Yamaha put in a SERIES DIODE SNUBBER........ready for this.......inside the wiring harness.  The Massimo 500 units have this diode on the passenger side wiring harness trunk line about half way down the vertical run of the wrapped harness bundle (buried inside the bundle to boot).....along with a wire color change at the diode.  Let's make it easy here!!!!!!!!!

Not worth digging and cutting the wrap for the diode.  Feed is the ignition switch ON lead.  When the diode OPENS, the circuit end at the diode.  I would tie a wire to the IGN switch ON lug, fuse with a inline 10 A, and then to the itty bitty red/blk wire.  Do this jack leg fix and then jumper the fan thermo switch to test....and don't look back.

[T-boss 410]

So, what's the diode for?

[Bill L]

The diode in the harness makes sense but I wonder why it does not show up in the wire diagram. I saw 2 diodes in the fuse box, not sure what they do. You are 100% correct to rewire the fan circuit and walk away from the problem. I tapped off the dash power socket as it is fused and the cooling fan uses low amps. I just like things to be correct. Thanks for the reply.

[Bill L]

When you are driving your utv the wind turns the fan making it a generator so they add a diode to prevent back feed to the electrical system. Just my thought, might be there for another reason.

[Ben1098]

This SERIES snubber diode is to BLOCK the reverse EMF (voltage spike) created when the power is interupted by the thermo fan switch (current stops and the magnetic field of the DC motor collapses).

In industrial applications with the control voltage circuits using 24 VDC,  the relays will have a SHUNT snubber diode across the coil relay terminals (cathode on the + 24 v terminal and the anode to the - side..........that is put in backwards.  The PLC's electronic driver switch, hates to have a back hit from the relay coils turn off (- spike components of the waveform) EMF spike.  120 VAC control voltage circuits relays do not require the diode (would fry on power up).

A good visual example is to take an old style Ignition coil and feed 12 Vdc to the + post with and the - or gnd post tied to the - side.  Coils were actually 6-8 V and the resistance wire in the harness (GM) or the Chrysler ballast block dropped the voltage to 6 V.  Touch and remove the +12 v feed wire....notice the reverse voltage arc flash.....better yet, for a shocking example of what NOT TO DO is grab a good ground and touch the bare wire end of the feed when opening the circuit....the hole in your finger tip will grow back.  The magnetic field from the current flow is stored energy........cut the current flow.....the energy has to go somewhere (other than to the high voltage side of the coil.  That is why points burn up with a pit and a mound.  The size of the capacitor (condenser) is "matched" to the ignition coils "L".  The capacitor value size above or below the "ideal match" value will result in the deposit (triangle mound) to be on the base contact or the movable arm contact.  The worst thing to do to an old points ignition motor.....TUNE UP.  New points and condenser.  If the points had little deposit transfer, the capacitor was a good match.......long point service life......only to be thrown away and a new RANDOM value capacitor installed THAT NIGHT NOT BE A GOOD MATCH.  Time to quit.