So I have a 389 with a 6nz in it recently it started to make a noise right before the ac kicks the engine fan on and it only does it with the ac on if you hit the fan switch it does not do it best way to describe noise it sounds like a train horn that barely has the valve open what could this be Thanks in advance
Humming when ac kicks on engine fan
Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by Blue2547, May 18, 2021.
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Hose to fan hub leaking ?
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If the A/C is kicking the fan on, and that's the only time you hear the noise, could it be your expansion valve?
Trucker61016, Blue2547 and skallagrime Thank this. -
(Sorry gpd, just wanted to finish that line of thinking so people know WHY that would happen)God prefers Diesels Thanks this. -
Trucker61016 Thanks this.
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The fan normally kicks on when the refrigerant pressure reaches 250 PSI.
The pump should shut off at 300 PSI to protect the system. I am wondering
if the switch is failing and turning the fan on when the pressure is too highGod prefers Diesels Thanks this. -
Gas to liquid and back is weird, especially when we start tampering with it in applied engineering.God prefers Diesels Thanks this.
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