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We have a John Deere 850D that is getting hot. The fan is not coming on. Don't know if its the fan or the fan switch. Is there a way to check the fan to see if it is it not working? Or check the fan switch?
 

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Disconnect the electrical connector at the fan and run 12volts directly to the fan. If it runs at least you know it is good.

The cooling fan is protected by a 25 amp fuse. Is it OK

The radiator fan temperature switch (closing temperature)...... 199 +/-5 F

Engine coolant temperature light switch(closing temperature)....232 +/- 5 F

The radiator fan is switched via a relay.

There are two coolant switches. One for fan and the other is for the dash light.

1. Are you getting 12 volts at the coolant sensor when above its trip point? If yes the coolant sensor is OK

2. Is there 12 volts on the red relay supply wire from the fuse block? If yes, fuse is OK. If no, check the 25 amp fuse or corrosion at the fuse block.

3. Is there 12 volts at the red fan supply wire when engine is above trip point? If yes fan motor is suspect. If no and the other two above are ok, likely to be the relay.
 

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Iowafarmersteve,

If you private message your email I can forward a few pages of the electrical diagram in PDF format.

200mph
 

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OK THANKS. My e-mail is [email protected] Got the fan running now. There was a mud dabbers wasp nest stuck on the fan bracket that would not let the fan turn. Got it took off and fan will turn now when I put power to it. I think the thermostat is stuck shut now. As the hot light will come on now before the radiator get warm. Picked up a new thermostat tonight but haven't got it in yet. Hope it hasn't hurt the relay now as it had blown the 25 amp fuse. But would still like the pdf of the wiring diagram. Will let you know if the thermostat fixes it. Thanks Steve
 

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Iowafarmersteve,

PDF sent. Please confirm receipt as the file size is over 10Mb and I'm on a very unreliable internet connection.

Hope you solve your overheating problem. Are you certain the water pump is turning (pumping)?

Good luck!
 

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Thank so for letting me know it was received.
 

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The thermostat fixed it. Every thing is working as it should now. Now we don't have to take the cab less one to feed cattle when the weather is bad. Thanks Steve
 

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Iowafarmersteve,

If you private message your email I can forward a few pages of the electrical diagram in PDF format.

200mph
Could you send me that PDF the fan motor works in our 855d gator but we are getting no volts to the motor. Would a closed radiator cause it to not get voltage for some reason? [email protected]
 

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Did you check the fuse and fuse holder electrically? Ditto with the relay and radiator temperature switch.

The temperature switch that turns on the radiator (sends signal to relay) is located in the radiator. If the temp switch is jumped at its connector, the fan should turn on. (This would mimic a hot engine or made temperature switch)

Post results of your voltage checks and hte simple test above.
 

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I've change the temperature switch and the thermometer/sensor located at the thermostat. I am reading temperature on the display screen, however when the gauge, reaches 4 bars (when switch should activate) I am getting no voltage. My boss told me to send that.
 

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Did you check the fuse and fuse holder electrically? Ditto with the relay and radiator temperature switch.

The temperature switch that turns on the radiator (sends signal to relay) is located in the radiator. If the temp switch is jumped at its connector, the fan should turn on. (This would mimic a hot engine or made temperature switch)

Post results of your voltage checks and hte simple test above.
I've change the temperature switch and the thermometer/sensor located at the thermostat. I am reading temperature on the display screen, however when the gauge
reaches 4 bars (when switch should activate) I am getting no voltage.
 

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I've change the temperature switch and the thermometer/sensor located at the thermostat. I am reading temperature on the display screen, however when the gauge
reaches 4 bars (when switch should activate) I am getting no voltage.
Can you be clearer on where you're seeing no voltage?

In post #10, suggested "Did you check the fuse and fuse holder electrically? Ditto with the relay and radiator temperature switch."

What are the results of this suggestion. By results, I'm asking for voltage readings. Is there battery voltage supplying the fuse(s)? Is there battery voltage to the relay?

Can we assume the coolant system is full with no air pockets that could prevent thermal switch from operating correctly?
 
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