Need Help! Hot Wiring The Cooling Fan...
10-25-2010, 03:34 PM
#1
Racer
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Need Help! Hot Wiring The Cooling Fan...
The cooling fan is not coming on. Relay terminals behind fan appear to be melted on the female end. Does anyone have a wiring schematic for the cooling system? Can someone explain in explicit detail how to hot wire the fan in order to confirm whether it's working or not. Pics on how and what will greatly help as I can't afford any mistakes with wiring.
Already used the search function... It's a great tool, but hasn't been of any help in the specifics I'm looking for.
Already used the search function... It's a great tool, but hasn't been of any help in the specifics I'm looking for.
10-25-2010, 05:04 PM
#2
Burning Brakes
10-25-2010, 05:23 PM
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The Search tool can be very useful 
Look at my reply there; 20 bucks says it is your exact problem too.
Last edited by PowerLabs; 10-25-2010 at 06:49 PM.
10-25-2010, 08:24 PM
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Take care buddy...
10-25-2010, 09:45 PM
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The fan motor is a stepper motor and it is controlled by a Pulse Width Modulator (PWM) module; the shiny metal box bolted on to your fan casing. The fan circuit is exceedingly simple: The PCM sends out a square wave signal to that shiny metal box via a thin gauge green wire (turns red after the first plug; still easy to identify because it is the only thin wire there), the shiny metal box has 12V (power AND ground) available to it at the plug at ALL TIMES (even with the car off), the box simply switches power on and off to the motor at a frequency determined by that square wave signal, which, in turn, is being commanded by the PCM itself, directly. There is a 60A fuse on the line (found on your fuse box) and nothing else. You can jump it by simply jumping the two black wires and the two red wires on the PWM plug, BUT, as I said before, when you pull the plug, it should be quite obvious where the problem is. There are only 3 wires: Power, Ground, and signal, and at the PWM module you have two power (From car and To fan), two ground (from car and to fan), and, again, one signal (from PCM). Again, as I said, the "from car" ground and power come right off the fuse box and are always live.You already said the female connector on the plug is molten. This is about as common as candy in haloween on these cars. I've explained why on the other thread so I'll save myself the typing; but take my word for it; it is the problem, soldering the wires is the solution, and it will come back if you don't
Last edited by PowerLabs; 10-25-2010 at 09:50 PM.
10-26-2010, 10:10 AM
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There is no fan relay on C6 Corvettes The fan motor is a stepper motor and it is controlled by a Pulse Width Modulator (PWM) module; the shiny metal box bolted on to your fan casing. The fan circuit is exceedingly simple: The PCM sends out a square wave signal to that shiny metal box via a thin gauge green wire (turns red after the first plug; still easy to identify because it is the only thin wire there), the shiny metal box has 12V (power AND ground) available to it at the plug at ALL TIMES (even with the car off), the box simply switches power on and off to the motor at a frequency determined by that square wave signal, which, in turn, is being commanded by the PCM itself, directly. There is a 60A fuse on the line (found on your fuse box) and nothing else. You can jump it by simply jumping the two black wires and the two red wires on the PWM plug, BUT, as I said before, when you pull the plug, it should be quite obvious where the problem is. There are only 3 wires: Power, Ground, and signal, and at the PWM module you have two power (From car and To fan), two ground (from car and to fan), and, again, one signal (from PCM). Again, as I said, the "from car" ground and power come right off the fuse box and are always live.
You already said the female connector on the plug is molten. This is about as common as candy in haloween on these cars. I've explained why on the other thread so I'll save myself the typing; but take my word for it; it is the problem, soldering the wires is the solution, and it will come back if you don't
Warning: I will drink $20 worth of said adult beverages next time I'm over if I am right
The fan motor is a stepper motor and it is controlled by a Pulse Width Modulator (PWM) module; the shiny metal box bolted on to your fan casing. The fan circuit is exceedingly simple: The PCM sends out a square wave signal to that shiny metal box via a thin gauge green wire (turns red after the first plug; still easy to identify because it is the only thin wire there), the shiny metal box has 12V (power AND ground) available to it at the plug at ALL TIMES (even with the car off), the box simply switches power on and off to the motor at a frequency determined by that square wave signal, which, in turn, is being commanded by the PCM itself, directly. There is a 60A fuse on the line (found on your fuse box) and nothing else. You can jump it by simply jumping the two black wires and the two red wires on the PWM plug, BUT, as I said before, when you pull the plug, it should be quite obvious where the problem is. There are only 3 wires: Power, Ground, and signal, and at the PWM module you have two power (From car and To fan), two ground (from car and to fan), and, again, one signal (from PCM). Again, as I said, the "from car" ground and power come right off the fuse box and are always live.You already said the female connector on the plug is molten. This is about as common as candy in haloween on these cars. I've explained why on the other thread so I'll save myself the typing; but take my word for it; it is the problem, soldering the wires is the solution, and it will come back if you don't
Warning: I will drink $20 worth of said adult beverages next time I'm over if I am right
Just a thought, but will some basic speaker wire suffice just to test the fan motor?
10-26-2010, 12:25 PM
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For a split second it definitely will. Try and keep the motor running with speaker wire though and you'll melt the insulation off and start a fire.
10-26-2010, 01:30 PM
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When you hardwired yours, did you cut the connectors off and use the existing wires, then solder it together?
10-26-2010, 06:08 PM
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10AWG would be plenty. But if all you want is to just verify that the fan works, even a simple paperclip in between both grounds and then both positive wires at the plug would do. Just don't leave it on for long; blip the fan on; it'll either work or not work; there is no need to keep it running if it works.
I actually used a tiny screwdriver to pop the spades off the connector, then I cut the wires as close to the spades as possible, stripped them, and soldered them into the PWM controller. For the top plug, I removed the spades from both connectors, coated them in solder primer, plugged them in, heated them with a small blowtorch and soldered them together. I used heat shrink to protect them and then taped over the heat shrink. No way it is coming apart again! Unless I need to service something, in which case I will de-solder it.
06-29-2013, 05:34 PM
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There is no fan relay on C6 Corvettes The fan motor is a stepper motor and it is controlled by a Pulse Width Modulator (PWM) module; the shiny metal box bolted on to your fan casing. The fan circuit is exceedingly simple: The PCM sends out a square wave signal to that shiny metal box via a thin gauge green wire (turns red after the first plug; still easy to identify because it is the only thin wire there), the shiny metal box has 12V (power AND ground) available to it at the plug at ALL TIMES (even with the car off), the box simply switches power on and off to the motor at a frequency determined by that square wave signal, which, in turn, is being commanded by the PCM itself, directly. There is a 60A fuse on the line (found on your fuse box) and nothing else. You can jump it by simply jumping the two black wires and the two red wires on the PWM plug, BUT, as I said before, when you pull the plug, it should be quite obvious where the problem is. There are only 3 wires: Power, Ground, and signal, and at the PWM module you have two power (From car and To fan), two ground (from car and to fan), and, again, one signal (from PCM). Again, as I said, the "from car" ground and power come right off the fuse box and are always live.
You already said the female connector on the plug is molten. This is about as common as candy in haloween on these cars. I've explained why on the other thread so I'll save myself the typing; but take my word for it; it is the problem, soldering the wires is the solution, and it will come back if you don't
Warning: I will drink $20 worth of said adult beverages next time I'm over if I am right
The fan motor is a stepper motor and it is controlled by a Pulse Width Modulator (PWM) module; the shiny metal box bolted on to your fan casing. The fan circuit is exceedingly simple: The PCM sends out a square wave signal to that shiny metal box via a thin gauge green wire (turns red after the first plug; still easy to identify because it is the only thin wire there), the shiny metal box has 12V (power AND ground) available to it at the plug at ALL TIMES (even with the car off), the box simply switches power on and off to the motor at a frequency determined by that square wave signal, which, in turn, is being commanded by the PCM itself, directly. There is a 60A fuse on the line (found on your fuse box) and nothing else. You can jump it by simply jumping the two black wires and the two red wires on the PWM plug, BUT, as I said before, when you pull the plug, it should be quite obvious where the problem is. There are only 3 wires: Power, Ground, and signal, and at the PWM module you have two power (From car and To fan), two ground (from car and to fan), and, again, one signal (from PCM). Again, as I said, the "from car" ground and power come right off the fuse box and are always live.You already said the female connector on the plug is molten. This is about as common as candy in haloween on these cars. I've explained why on the other thread so I'll save myself the typing; but take my word for it; it is the problem, soldering the wires is the solution, and it will come back if you don't
Warning: I will drink $20 worth of said adult beverages next time I'm over if I am right
When you said ( The PCM sends out a square wave signal to that shiny metal box via a thin gauge green wire (turns red after the first plug
do you mean there should be 12 volts to the green wire? My fan is not working, plugs are not melted. The green wire is showing to be grounded... I can throw 12 volts to it and the fan will come on.. What activates the thin green wire?
01-16-2016, 05:46 PM
#13
Crappy that this thread died before it was fully answered, so I thought I'd complete it.
The thin PWM wire gets a pulse width modulated square wave of -12V from the ECU when the ECU decides the fan should be on. It's either grounded or open.
This means to test the fan plus fan controller, you can tap into the thin wire at the fan controller (maybe stick a paper clip in the back of the connector where the thin wire goes in, or install a tap connector), and short it to ground (touch it to the crossmember). You'll see the fan come on, then stop. That's because you're not giving the controller a pulsed square wave, only a constant signal. If you let go and touch it again, the fan will come on again, then go off. If you touch the wire to the crossmember and let go in quick succession, the fan will continue to run. To get it to run faster, let go quickly and touch it for longer, let go quickly, touch it for longer. The fan will run faster, because it's getting a square wave that's grounded more than 50% of the time. And that's how the fan speed controller works!
To get back to the OP's question, the easiest way to hotwire the fan is:
-disconnect the big connector from the fan control module at the bottom right of the fan, and leave it disconnected
-make two short jumper wires (1" to 2" long) of 10 gauge wire with male spade connectors on both ends
-jumper the two red wires together, and jumper the two black wires together (ie: plug the first jumper wire's spades into the first and second slot, and the second jumper wire's spades in the third and fourth slot)
-the fan will come on
-for bonus points, if you want to wire the fan to a manual switch, then replace one of the jumper wires with a relay, and run the relay control wire(s) to a switch in the cabin.
-you could try running 10 gauge wire to a switch inside, without a relay, but the switch might burn out given the large amount of current going through the fan when it's on full power! So a high capacity relay is recommended (50A or 60A).
The problem in my case was that the PWM signal was interrupted somewhere along the way, so the controller never got a signal from the ECU, and my fan would never turn on. So I ran my own wire directly from the ecu terminal to the pwm controller, bypassing the car's wiring. You will have to look up in the schematics which ECU pin to tap into.
Another point: PowerLabs said the fan motor is a stepper motor. It must not be if jumping the two black and two red wires makes it run. It must be a normal motor. A stepper motor would only step one cog and stop if you applied constant voltage. Also, stepper motors have more than two terminals to drive them.
The thin PWM wire gets a pulse width modulated square wave of -12V from the ECU when the ECU decides the fan should be on. It's either grounded or open.
This means to test the fan plus fan controller, you can tap into the thin wire at the fan controller (maybe stick a paper clip in the back of the connector where the thin wire goes in, or install a tap connector), and short it to ground (touch it to the crossmember). You'll see the fan come on, then stop. That's because you're not giving the controller a pulsed square wave, only a constant signal. If you let go and touch it again, the fan will come on again, then go off. If you touch the wire to the crossmember and let go in quick succession, the fan will continue to run. To get it to run faster, let go quickly and touch it for longer, let go quickly, touch it for longer. The fan will run faster, because it's getting a square wave that's grounded more than 50% of the time. And that's how the fan speed controller works!
To get back to the OP's question, the easiest way to hotwire the fan is:
-disconnect the big connector from the fan control module at the bottom right of the fan, and leave it disconnected
-make two short jumper wires (1" to 2" long) of 10 gauge wire with male spade connectors on both ends
-jumper the two red wires together, and jumper the two black wires together (ie: plug the first jumper wire's spades into the first and second slot, and the second jumper wire's spades in the third and fourth slot)
-the fan will come on
-for bonus points, if you want to wire the fan to a manual switch, then replace one of the jumper wires with a relay, and run the relay control wire(s) to a switch in the cabin.
-you could try running 10 gauge wire to a switch inside, without a relay, but the switch might burn out given the large amount of current going through the fan when it's on full power! So a high capacity relay is recommended (50A or 60A).
The problem in my case was that the PWM signal was interrupted somewhere along the way, so the controller never got a signal from the ECU, and my fan would never turn on. So I ran my own wire directly from the ecu terminal to the pwm controller, bypassing the car's wiring. You will have to look up in the schematics which ECU pin to tap into.
Another point: PowerLabs said the fan motor is a stepper motor. It must not be if jumping the two black and two red wires makes it run. It must be a normal motor. A stepper motor would only step one cog and stop if you applied constant voltage. Also, stepper motors have more than two terminals to drive them.
Last edited by steel_3d; 01-19-2016 at 02:35 AM.
01-17-2016, 11:36 AM
#14
Instructor
I'll add my experience with a similar problem - which turned out to be bad grounds.
https://www.corvetteforum.com/forums...won-t-run.html
martysauto provided some very useful guidance on testing the circuit.
https://www.corvetteforum.com/forums...won-t-run.html
martysauto provided some very useful guidance on testing the circuit.
08-17-2020, 10:49 PM
#16
Drifting
The suggestion to install a separate fuse box is a good idea. I did in on my 68 convert with big block and electric fan. The Pulse Width Modulation controller is also a good idea that I did not consider, but will add to my system. The fan comes on suddenly with a big power surge and starting them slowly will help.
