After 10 years of ...... resting, my 91 Z-28 is going back together with a nice fresh Corvette 5.7. I have two wires down by the starter, one is for the Knock Sensor, and I believe the other to be for the fan switch. I don't remember where the switch and sensor go? I have the Knock Sensor in the block drain hole, and don't know where the fan switch goes? Do I have the wrong sensor in the drain hole? Thanks for your help. Cbob
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Ghettobird52
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Mar 7, 2020
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Knock sensor sounds like its in the correct location, bottom passenger coolant drain hole on block. The fan switch is on the head between cylinders 6&8, also a coolant hole.Originally Posted by cbob
After 10 years of ...... resting, my 91 Z-28 is going back together with a nice fresh Corvette 5.7. I have two wires down by the starter, one is for the Knock Sensor, and I believe the other to be for the fan switch. I don't remember where the switch and sensor go? I have the Knock Sensor in the block drain hole, and don't know where the fan switch goes? Do I have the wrong sensor in the drain hole? Thanks for your help. Cbob 
fan switch hole is in the passenger side head between #6 & #8 plugs. It's in the same position relative to the head that the temp gauge sender is in the driver side head. Wire going to it should be green with white stripe
OK, Got it. My head has a plug in the hole, so the Vette must have put the sensor somewhere else? Of course now it's going to be a bitch to get the plug out 
If my memory is correct, the computer turns the first fan on according to the temp programmed into the memcal, or when the AC is turned on, then the fan switch brings on the second fan? Or do I have that backwards?
If my memory is correct, the computer turns the first fan on according to the temp programmed into the memcal, or when the AC is turned on, then the fan switch brings on the second fan? Or do I have that backwards?
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Ghettobird52
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Mar 7, 2020
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If my memory is correct, the computer turns the first fan on according to the temp programmed into the memcal, or when the AC is turned on, then the fan switch brings on the second fan? Or do I have that backwards?
I wont be much help with the two fan setup as my firebird came with the single fan option. Heres what i do know;Originally Posted by cbob
OK, Got it. My head has a plug in the hole, so the Vette must have put the sensor somewhere else? Of course now it's going to be a bitch to get the plug out If my memory is correct, the computer turns the first fan on according to the temp programmed into the memcal, or when the AC is turned on, then the fan switch brings on the second fan? Or do I have that backwards?
The fan switch in between 6&8 acts as a heat probe that tells the computer its temp. Whenever the coolant between cylinders 6&8 reaches whatever is programmed in the computer for temp turn on point for fan, it turns fan on. So technically from what i know in a stock setup, the fan turn on point can be changed via computer and it uses that temp switch inbetween cylinders 6&8. it doesnt use the coolant temp sensor to turn on the fan, from what i know.