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My original cooling fan set up had spal fans hardwired to the controller. The original wiring from pcm to controller has hardwired. The plug that has issues with melting on factory set up was bypassed and wires soldered. What factory wires are used to connect the controller for the Prospeed dual fan set up to pcm?
Where you bypassed the plug that burns up, use that small wire to connect to the new SSD relay on the prospeed fans. That small wire is the signal wire to the ECM.
There are 2 wires that connect to the prospeed controller. What other wire do I use to connect? The bigger black wire is the ground and bigger red wire power.
Right hand side of the PWM connector connects to the OWM wiring connector to pull the ECM control signal from the ECM only.
On the left hand side wiring connector from the PWM, will have Black wire that need to be connected to ground on the chassic, and the red wires that need to be connected to 12v positive source (engine fuse box terminal will work).
If you burnt up the OEM connector on the side of the radiator, then you can buy a replacement connector to keep that OEM connector to keep it all plug and play. GM sells them wired so you can just solder the tail it back to the oem wires with heat shrink wraps, or you can just buy the plug kit with pins instead.
The prospeed fans get there power direct wire from fuse box power Conection. Also has ground that connects to ground near lower radiator. The connection from controller to pcm only has 2 wires. The pcm Barnes has three. One is not used.
The prospeed fans get there power direct wire from fuse box power Conection. Also has ground that connects to ground near lower radiator. The connection from controller to pcm only has 2 wires. The pcm Barnes has three. One is not used.
Correct, the output side of the PWM get its power from the battery and chassis ground directly, and the input control side of the PWM is only grabbing the ECM radiator control wire, and 12 volt power.
So the fans get wired directly to the battery positive through the PWM, and the PWM is just control the postive wires of the fans to pulse the fans.
So this is the reason that the PWM needs major power on the output side of the PWM since it will be the side that is seeing all the load of the fans, while the input control side of the PWM is pulling minimal power from the ECM and small ground wire to pulse it SSR instead.
What confuses me is that the 2 outside wires of the origin factory harness plug are red/black and green. The inside wire of the harness is black. In the new controller only the 2 outside wires is used. The in side wire on the connection is empty. so small red wire is trigger and red and black ground. Black wire in center of factory oem connector is 12 volt? I always thought ground wire was black. See pic.
I would recommend wiring the power feed wires for the fans directly to the battery rather than the fuse box stud. Without going into electronics overload, the PWM switching of the fans on/off creates LOTS of noise that will cause your ECM to read incorrect voltage levels and will throw off various things on the car. The battery serves as a large enough capacitor to dampen this out so the ECM won't see it.
Then again, if your battery doesn't have provisions for attaching ring terminals, you may not have another option.
Thanks for the info. I have the Mechman 240 amp alternator with direct wire to the fuse box post. Will that work?
The alternator itself isn't the problem. To illustrate what I'm talking about, here are some scope grabs:
fuse box voltage with fan ramping from OFF to ~22% duty cycle fuse box voltage with fan at ~33% duty cycle fuse box voltage with fan switching off (manually)
As you can see, the voltage is very stable at ~ 14.2 V when the fan is off. When the fan is on at some medium duty cycle, your ECM "sees" anywhere from 14.5 V to 12.5 V, depending on when it samples the voltage. This affects all sorts of things, from injector pulse widths to timing to things that are probably buried in the OS invisible to any tuner.
Attaching the fan wires to the battery will produce an inherently more stable waveform because the battery will absorb much of this voltage fluctuation.
The cause of this is that the fans are switched on and off very rapidly in ~ 60 A pulses. Without going too crazy here, this causes big positive and negative voltage spikes every time the fans are pulsed on and off. This can be solved/mitigated by the installation of a large flyback diode at the fan. I brought this issue up to D3PE/Prospeed some time ago, before I bought the fan system, but it was dismissed as "not a problem". It very obviously is. When I have some time to get the car on the lift next week, I'll take some readings of what things look like with the wires on the battery and also how things look with the flyback diode installed. If things look good enough, I'll be reaching out to Prospeed about it, and I may post a tutorial on how to fix this issue if they are not receptive.
I still think this is by far the best cooling option out there for the C6 platform. I'm running mine with a standard size DeWitts radiator and it performs incredibly, except for the electrical issues it causes.
EDIT: looking at the solid-state relay datasheet posted above, on page 2, there is a note saying "Inductive Loads Must be Diode Suppressed". A fan is a large DC motor which is a very large inductive load.
Last edited by njedwardz; May 22, 2019 at 07:26 PM.
I would recommend wiring the power feed wires for the fans directly to the battery rather than the fuse box stud. Without going into electronics overload, the PWM switching of the fans on/off creates LOTS of noise that will cause your ECM to read incorrect voltage levels and will throw off various things on the car. The battery serves as a large enough capacitor to dampen this out so the ECM won't see it.
Then again, if your battery doesn't have provisions for attaching ring terminals, you may not have another option.
I just recently replaced the battery on my 2017 Yukon Denali (battery went completely flat without a battery tender over a 2 month time period... like 1.6vdc!). GM is using a really nice snap-on positive terminal block on their batteries for those connections that require a direct battery connection. I would also fuse this connection.
Those scope meters are nice!
I wonder if an AGM battery would also exhibit the same capacitive characteristics as a standard lead-acid battery?
Last edited by mikeCsix; May 31, 2019 at 11:14 AM.
I finally had some time to put the car on the lift today, and I found out that prospeed actually DOES install flyback diodes! Which is good! I can’t imagine what the noise would look like if they didn’t.
Since I had the heatshrink cut off already, I decided to replace them with the beefier/faster diodes I had ordered. I did not notice much difference in the noise.
The scope grabs are taken directly at the fan this time instead of at the fuse box. Tomorrow I will add the PWM signal on a second trace for overlay to see exactly where those spikes are from.
As an EE, I’m honestly a bit confused by why there is still so much noise here. Will do some thinking and consultation.
Diodes installed by ProSpeed New Schottky diodes installed Zoomed in view showing pulses resulting from ~125 Hz PWM Zoomed out view showing lots of noise still present
Wow what a difference. Never saw coolant temps get over 190 on a 92 degree day.
Can the Prospeed be installed on a stock radiator and shroud by removing from bottom of car? I have the car on a lift at the moment. If so...anyone have removal pics?
Last edited by TTZ06VETTE; Jun 10, 2019 at 01:51 PM.
An interesting appnote for sure. Implementing this would require converting to a high-side drive as well. I am interested this approach.. maybe I'll get around to building a proof of concept one day..
I'm almost wondering if swapping the SSR to a high-side config would change anything on its own.
Last edited by njedwardz; Jun 11, 2019 at 02:42 PM.
Just did this last month with ECS blower and stock radiator. Only issue is had to reroute the heater core hose to the top of blower rather than leave it underneath. Cut out the factory tee, use a pex tee and clamps off the 90 position then run new hose over the blower. Haven't had super hot humid yet but at 88 outside and ac on full I topped out at 210. Great improvement so far.
Prospeed Cooling fan install wiring help
