Radiator fan not coming on on SP1 HELP - Honda RC51 Forum : RC51 Motorcycle Forums
 
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post #1 of 3 (permalink) Old 08-24-2010, 09:28 PM Thread Starter
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Radiator fan not coming on on SP1 HELP

I live in Texas and bought this RC a few months ago. Love it, but the other day at a stop light my heat light came on. I switched the temp gauge on and saw 255! thankfully the light turned green and I took off, and the bike was air cooled at about 210 - 230 the rest of the ride, depending on how fast I was going. It was about 110 outside.

I took the bike home and let it idle to 218 and the fan did not turn on. I reached in there to turn the blades and the fan was very snug up against the radiator, is this normal? I could turn it but it seemed like it would be stressful for a motor to have this resistance. Checked and fuse and it was blown, but even after I changed it fan still does not work.

I tried to hotwire the fan to the battery to test it but I got somewhat confused on which plug to wire. I blew another fuse in the process. The only one that seemed to possibly be my source of power was a small black plug that plugs into a housing on the front of the left radiator. It has a black/blue wire and a green wire.

Anyway, What should I do to test this? Any help is greatly appreciated; i don't want to burn up my motor. Love this bike to death.
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post #2 of 3 (permalink) Old 08-24-2010, 11:06 PM
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The fan should spin very easily with a flick of your finger tip.
The fan is close to the radiator, but shouldn't rub against the radiator.
If there is no obstruction, and the fan is difficult to turn, then the fan motor bearings are shot. Time to replace the motor.

You'll need to drain the coolant and remove the radiator as the fan and it's mount are bolted to the radiator.
Once you've removed the radiator, then it's easy to swap out the motor.

The SP1's only have one fan, and it's directly controlled by the fan switch which is mounted into the left radiator. Very simple.

The SP2's have two fans, and are controlled by a temperature sensor and the ECU which signals the fan relay to activate the fans. More complicated.

To check the SP1 fan motor:
1) With no blown fuse and engine at operating temperature, pull the connector from the fan motor switch mounted into the left radiator, then ground the connector. The fan should run.
2) If the fan still won't run, measure the voltage at the black/blue and green wires on the 2-pole fan motor connector just below the fan switch. You should read battery voltage.
- If there is battery voltage, the fan motor is bad.
- If there is no battery voltage, then check for blown fuse or open circuit in the wiring.

Last edited by SubSailor; 08-24-2010 at 11:18 PM.
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post #3 of 3 (permalink) Old 08-25-2010, 03:58 AM
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Quote:
Originally Posted by SubSailor View Post
The fan should spin very easily with a flick of your finger tip.
The fan is close to the radiator, but shouldn't rub against the radiator.
If there is no obstruction, and the fan is difficult to turn, then the fan motor bearings are shot. Time to replace the motor.

You'll need to drain the coolant and remove the radiator as the fan and it's mount are bolted to the radiator.
Once you've removed the radiator, then it's easy to swap out the motor.

The SP1's only have one fan, and it's directly controlled by the fan switch which is mounted into the left radiator. Very simple.

The SP2's have two fans, and are controlled by a temperature sensor and the ECU which signals the fan relay to activate the fans. More complicated.

To check the SP1 fan motor:
1) With no blown fuse and engine at operating temperature, pull the connector from the fan motor switch mounted into the left radiator, then ground the connector. The fan should run.
2) If the fan still won't run, measure the voltage at the black/blue and green wires on the 2-pole fan motor connector just below the fan switch. You should read battery voltage.
- If there is battery voltage, the fan motor is bad.
- If there is no battery voltage, then check for blown fuse or open circuit in the wiring.

+1 to SubSailor

The only thing I would add is the engine does not have to be on or warm to check the fan. The key does need to be on. You also may have a bad ground on the radiator. This is supplied through the black connector. You may want to ground the wire from the fan motor switch to the battery ground using an extra long wire.

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