2004 500 cooling fan not coming on.

[Gwbarm]

Unplug the fan from the wiring harness and run extra wires from the battery and attach to the fan plug.

[Mech]

Gw's suggestion will be the way to test the fan.

The fan and the temp light though both have their own temp sensors, so if it's just the light playing up, it might be it's switch.

output.pdf

[BLR81471]

I got the fan to start when putting 12V to it. I have changed the sensor at the bottom of the radiator. It still overheats.

What should i try next? 

Is the Diode a cause?

Thermostat?

What triggers the fan to turn on? Because it will begin steaming and the fan wont turn on.

[Mech]

If the diode was open circuit it would stop the fan coming on.

Check power is getting to the temp switch with a test light, not a gauge, then unplug the switch and bridge across the plug on the bikes wiring with a wire. That should make the fan go. If the fan doesn't go then, check there is power getting to the fan's red wire using a test light. If there is power to the fan, bridge across the diode with a piece of wire and see if the fan goes. To bridge the diode you can just put a wire from black wire of the fan straight to a good earth.

[Gwbarm]

There should be 12 v going to the sensor, on the wire that plugs into the sensor, when temp gets hot enough the sensor makes contact and sends 12v to the fan. It definately could be the thermostat, with the radiator cap off get it up to operating temp and see if there is water movement within the radiator if there is the thermostat is working. Im not sure about the diade i havent looked at a wiring diagram.

[Mech]

Diagram up further. The diode's between the fan and earth.

[BLR81471]

15 hours ago, Mech said:

If the diode was open circuit it would stop the fan coming on.

Check power is getting to the temp switch with a test light, not a gauge, then unplug the switch and bridge across the plug on the bikes wiring with a wire. That should make the fan go. If the fan doesn't go then, check there is power getting to the fan's red wire using a test light. If there is power to the fan, bridge across the diode with a piece of wire and see if the fan goes. To bridge the diode you can just put a wire from black wire of the fan straight to a good earth.

What are you referring to when you say Temp Switch? I have a Temp Sensor on the bottom of the radiator. It leaves there with two plugs. One that goes to the fan and one that goes to the diode and the battery I assume?

If I disconnect the diode does that mean the fan will not operate at all? Has to be grounded in order for fan to operate?

[Mech]

There are two temperature sensing switches. One is wired back to the dash with a violet wire, and the other one has two red wires. The switch you are looking at is in the lower left of that wiring diagram I posted. 

The power for the fan comes from a fuse to the temperature sensing switch connector in a black wire with a red stripe (blk/red), Then the switch's wires are both red, and one of them comes back out of the switch and goes to the fan motor when the switch closes. It goes through the fan motor and comes back out on a black wire as far as the fan's connector where it turns into a black wire with a white stripe as far as the diode, and after the diode it's a black wire connected to earth.

And yes, the diode has to conduct to earth for the fan to operate.

Edited March 13, 2024 by Mech

[BLR81471]

On 3/13/2024 at 6:05 PM, Mech said:

There are two temperature sensing switches. One is wired back to the dash with a violet wire, and the other one has two red wires. The switch you are looking at is in the lower left of that wiring diagram I posted. 

The power for the fan comes from a fuse to the temperature sensing switch connector in a black wire with a red stripe (blk/red), Then the switch's wires are both red, and one of them comes back out of the switch and goes to the fan motor when the switch closes. It goes through the fan motor and comes back out on a black wire as far as the fan's connector where it turns into a black wire with a white stripe as far as the diode, and after the diode it's a black wire connected to earth.

And yes, the diode has to conduct to earth for the fan to operate.

Still trying to solve this problem.

Replaced the sensor on the bottom of the radiator.

Removed thermostat and tested it. It opens in boiling water then closes when cooled.

Check the Diode and it seems to test as required. .8 one way and infinite the other.

Checked Fan fuse and its good.

What do I need to do next? 

I have run the machine at idle for like 15-20 minutes and it begins to steam from radiator. The fan does not come on. Im not sure if there is anything else in the fan circuit that I need to check?

I see there is a sensor beside the thermostat with a single wire going into it. Is that the temp light sensor? Does that have any affect on the fan turning on?

How can I test my radiator cap to see if that has anything to do with my problem.

Any help would be greatly appreciate.

[Mech]

Have you looked at that wiring diagram I posted for you at #32?

There are two temp sensor switches, one has one wire and the other has two. They use different coloured wires.

If you follow the recommendations/test procedure in #34 it should find the fault with the fan, if there is a fault with the fan.

Most engines won't overheat in fifteen minutes of idling from cold. It may be that you have a blown head-gasket, faulty water pump,  blocked radiator, or a radiator that's dirty on the outside. If you take the radiator cap off and let it idle with a full to the brim radiator, there shouldn't be any bubbles coming up in the filler. I'd check that.

[BLR81471]

6 minutes ago, Mech said:

Have you looked at that wiring diagram I posted for you at #32?

There are two temp sensor switches, one has one wire and the other has two. They use different coloured wires.

If you follow the recommendations/test procedure in #34 it should find the fault with the fan, if there is a fault with the fan.

Most engines won't overheat in fifteen minutes of idling from cold. It may be that you have a blown head-gasket, faulty water pump,  blocked radiator, or a radiator that's dirty on the outside. If you take the radiator cap off and let it idle with a full to the brim radiator, there shouldn't be any bubbles coming up in the filler. I'd check that.

Yes I looked at the diagram and saw the two sensors. As I mentioned I’ve replaced the one in the radiator. Not sure how to test the other. Does it affect fan operation?

I’ve put power to the fan and it runs. Are you suggesting I should test this another way? Because I don’t understand your procedure in #34. If it powers on with direct voltage is there something I’m missing? 
how would I know if I blew a head gasket?

power seems good on machine when running. I’ve run it with radiator cap off and don’t notice bubbles but will try again. Maybe I’ll video it so you can see. 

[Gwbarm]

Does the temp light come on when the radiator start to steam

[BLR81471]

8 minutes ago, Gwbarm said:

Does the temp light come on when the radiator start to steam

Right now I have only had the machine on idle for like 20 minutes and had it lightly steam/overheat. Mainly because all the plastics are off. So i have not been out riding which is when it typically makes the red light come on. The last ride I was on before taking it apart it had the red light on and some pretty good steam.

[Mech]

#41 I'm not sure which sensor is fitted where on the bike. I only know one has one wire and one has two.

If putting power into the fan makes the fan run then the fan is ok. My test procedure is testing which place along the wiring system the disconnect is that's preventing it from going.

The most common sign of a blown head gasket is bubbles coming up in the radiator.

Steam could be caused by the air being very cold ? Warm water always looks like it's steaming if the air over it is cold enough. Even a farm pond can look like steam's rising up off it.

If the engine is really overheating in fifteen minutes of idling it could be the thermostat, the water pump, the head-gasket, a blocked or dirty radiator.

[Gwbarm]

Steaming to me means there is aa leak in the cooling system somewhere letting the steam escape, not sure if the fan would keep that from happening, i would try running the fan directly from the battery and see if it keeps it cool enough and prevent the light from coming on and steaming.

[Mech]

Good plan Gw..