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Discussion Starter #1
Can someone tell me at what temp the low speed fan should come on? or point me to an earlier discussion?
I don't believe my fan is coming on until the highspeed relay is engaged.
Thanks.
 

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Can someone tell me at what temp the low speed fan should come on? or point me to an earlier discussion?
I don't believe my fan is coming on until the highspeed relay is engaged.
Thanks.
Low speed fan comes on at 226 and off at 219. High speed comes on at 235 and off (back to low speed) at 226.

Running the AC will cause the cooling fan to run as soon as the system pressure reaches “normal” high side pressure.

It is quite common for the voltage dropping resistor inside the fan motor to have a mechanical failure. I have seen three instances of the 1 ohm internal resistor failure in the last year. If this happens, the fan will never go to low speed. The resistor failure is much more common than a relay failure.

My two cents,

Mike
 

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Discussion Starter #4
Mike,
Your point about the resistor is an interesting one. I replaced the stock fan last year with one of your fans, so does that problem still exist with your model fan?
THX
 

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Mike,
Your point about the resistor is an interesting one. I replaced the stock fan last year with one of your fans, so does that problem still exist with your model fan?
THX
No, that problem disappears with the change to my fan. The one ohm resistor is that massive 100 watt brown ceramic part inside the shroud. I have never seen one fail.

You may have a relay issue. You can test the relay by running the air conditioner in the driveway. When the system comes up to “normal” pressure, the fan will come on to low speed. Keep in mind that you will need to have warm enough temps to get the Freon head pressure up to 200 psi.....

Regards,

Mike
 

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Discussion Starter #6
So, I've done some troubleshooting on the fan situation and this is what I've found:

With the AC turned off, the fan does NOT kick in at all until the temp reaches 235. It stays on until the temp drops to 219, then the fan stops and the low speed fan does NOT kick in. (not good!)

With the AC on, the fan kicks in at 225 and stays on until the temp goes down to 219, at which time it shuts off. (which sounds like normal operation)

Does this sound to you or the others like a low speed relay issue or something else?
If its a relay, do you know the part number?
Thanks for your help, Mike
 

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So, I've done some troubleshooting on the fan situation and this is what I've found:

With the AC turned off, the fan does NOT kick in at all until the temp reaches 235. It stays on until the temp drops to 219, then the fan stops and the low speed fan does NOT kick in. (not good!)

With the AC on, the fan kicks in at 225 and stays on until the temp goes down to 219, at which time it shuts off. (which sounds like normal operation)

Does this sound to you or the others like a low speed relay issue or something else?
If its a relay, do you know the part number?
Thanks for your help, Mike
Since you did not specify anything about fan speeds...... I'm going to make a guess at the operation of the fan.

With the AC turned on, the fan comes on at high speed and then shuts off. I would wager that the fan never operates at low speed..... Operation with the AC turned on has absolutely nothing to do with water temperature.

At high speed, the fan will move a lot of air and make enough noise that you can hear it in the cabin with the windows up and the AC on.
At low speed, the fan will be absolutely silent.... even when you are standing alongside the truck with the hood open. You will probably have to look to see if it is actually spinning.

If I am correct, your low speed circuit inside the fan motor has failed..... I'm not convinced of a relay problem. In 12 years, I have only seen three bad relays.....

If you want to replace the relay, it is the black (30 amp) one on the driver's side inner fender.

Let me know how this turns out.

Mike
 
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