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Hey guys, I've got a 2009 Z06 with Fan issues. The car has a Dewitts radiator with the SPAL dual fan and factory fan module. A couple evenings ago I got stuck in traffic and the car got hot on me..it went from 220 to maxing out the gauge in about 30 seconds (fans never came on). I pulled the car over and shut it off, with steam and coolant spilling out of the overflow reservoir. I was close to home so I just waited for it to cool down and limped it back. Put in fresh oil and topped off the coolant yesterday, during which I inspected the infamous 3-prong fan connection that seems to be a widespread issue, and it seems ok, no melted plastic or anything. The center ground connection is very slightly discolored compared to the sides, but not physically damaged in any way. After inspection I plugged it back in and started the car to see if the fans would work, and miraculously they did. Temps stayed at ~200 idling in the garage.
Fast forward to today, I started the car to test the fans again and no bueno. Neither the A/C being on nor the temp getting to 220 turned the fans on. Jacked the car back up to re-inspect that plug (no change). I did hot-wire the fans at the module connection per this video:
and the fans worked. This tells me: (A) Everything "upstream" of that fan module connection is good, 3-prong connector and fuse included. (B) My issue lies with either the fan module itself or the ECM sending the signal to turn the fans on. My problem with this is how did they work yesterday and not today if either of these were the case...
I tested voltage at the power to the fan module connector (blue circle in pic below) and got 13 volts. I also tested at the trigger wire (red circle) and got 0 volts. Is that what I should expect with the car off?
All this to say I'm still not sure what's going on here but I have a slight hunch that I have an iffy connection at the 3-prong fan connector since that's such a common problem it seems. What am I missing here?
Last edited by Hawgdriver25; Feb 8, 2021 at 08:27 AM.
Reason: Wrong video link
OEM PWM controls the fan on the ground side, and the postive side will be 12 volt hot when the car is turned on.
Ref voltage comes for the ECM.
As for using the PWM on a dual fan set up, not really designed for that load, since the OEM fan uses about 18 amps, while a dual set up fans can pull over 40 amps isntead.
So my guess with OEM PWM in play, you may have burnt it, or may just be the up line coupler is burnt up instead.
As for the correct PWM controller for the dual fan set up so you don't burn up another OEM PWM again (look at my post #8 bottom for the needed ST relay that works with the ECM reference voltage) https://www.corvetteforum.com/forums...ring-help.html
After several shorted plug/wiring repairs I added DeWitts brushless single fan along with the DeWitts radiator and the wiring and cooling issues are long gone.
The single brushless fan bypasses the oem harness completely and draws way more airflow and runs more efficiently. Not a cheap upgrade however.
OEM PWM controls the fan on the ground side, and the postive side will be 12 volt hot when the car is turned on.
Ref voltage comes for the ECM.
As for using the PWM on a dual fan set up, not really designed for that load, since the OEM fan uses about 18 amps, while a dual set up fans can pull over 40 amps isntead.
So my guess with OEM PWM in play, you may have burnt it, or may just be the up line coupler is burnt up instead.
As for the correct PWM controller for the dual fan set up so you don't burn up another OEM PWM again (look at my post #8 bottom for the needed ST relay that works with the ECM reference voltage) https://www.corvetteforum.com/forums...ring-help.html
By up line coupler you mean the 3-prong connection on the passenger side of the radiator that tends to burn up, correct? That one looks good, with the center (ground) connection being very slightly discolored compared to the other two connections. Do you know of a way that I can test my OEM PWM for function? Like I stated above, the fans were working one day, and not the next, so it's possible that the PWM got burnt but I don't think I buy it.
The PWM will pulse the ground side to chassis, and the faster it pulses, the faster the fans will spin.
So if you have a meter that can show a load up to 50 amps, just pull the ground off the PWM to the chassis, wire it through the meter back to the chassic ground again, and look for the pulses on the meter amp reading. Hence turn on the A/C, which will turn on the fan when the motor is running. This way you don't have to wait for the engine to come up to temp before the ECM will kick the fan on.
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On the Solid state relay, you want the DC100 series to work with the ECM reference voltage (4 volt turn on, to 32 Volts), and the last letter with 2 numbers with be the amperage rating (that you want to de-rate as well). https://www.masterelectronics.com/cr...-45158261.html
So since are running a dual fan set up that can spike to above 40 amps for both fan at start up/running full blast, you want to run a DC100 relay rated at 60 amps.
So the solid state relay you need for the dual fan set up, will be a D100DC60. https://www.masterelectronics.com/crydom/dc100d60-45158261.html
Also, make sure to mount the relay to metal with heat transfer paste between the back of it and bare metal under it, and the metal you are mounting it to has enough area to work as a heat sink. Hence something like this, since the aluminum sheeting used for the fans, has enough material to work as a heat sink as well.
Last one, and if the fan is running, but motor is not cooling down, check your A/C condenser and radiator for gravel and sand that are stuck in there veins.
The down and dirty, pull the top cap off between the two off and tape up the front of the TB, and you have enough room to get a garden hose long reach spray wand with 90* tip between the two to wash such out. Hence start by spraying from the back sides of both, to drive the debris out the front's, since this is the way that the such got trapped into both, the flush out front to back next on both units next.
Top cap removed so you get between the two,
How much gravel and sand can get wedge in the veins.
I prefer a tip like this,since it gets into tighter spaces,
But the the radiator genie water wand will work for less money.
also, comes with the air spray wand that works around the shop for other needs as well.
Thanks, Dano! I do want to try one more thing before I pull the trigger on that project. Who can point me towards a scan tool that's not expensive but advanced enough to force the fans on for diagnostic purposes? If I can force the fans on with a scan tool and they work, then I'll know my problem is likely not the fan module but something with my tune.
Thanks, Dano! I do want to try one more thing before I pull the trigger on that project. Who can point me towards a scan tool that's not expensive but advanced enough to force the fans on for diagnostic purposes? If I can force the fans on with a scan tool and they work, then I'll know my problem is likely not the fan module but something with my tune.
Turning the A/C on while the motor is running, turns the fan on from the prospective of the ECM.
Short of that, you can cycle the fans with a Tech II (again, from the prospective of the ECM), so if you have a Windows 10 laptop, then VX GM Nano, that will come with cracked Tech2win.
Also, since its a MDI 1 clone, works with GDS2, Tis2000, and even TDS (which make it even better than a tech II clone, since it covers the GM cars all the way up to 2020).
Dano has some good suggestion here I think the PWM box could be gone I know I had one go on mine. The AC condensor will get clogged with stuff and can effect cooling. By you hot wiring the controller the fans to come on would suggest the controller is gone. I would also check the ground to the fan - it is right by the passenger side hood strut you will see a bunch of ground wires there bolted to the frame. Of course if you can fix it with a new controller box great. I did like the guy from Hawaii above and went with a 500 Watt (draws about 32 amps) brushless route and put it in a stock housing. I have a single wire there going to controller box so computer sees a fan is there. The actual control is done by a little PWM they sell you with the fan. In your case pursue the wiring and a new controller. I would also check the 60 amp fan relay in the under hood fuse box one guy on here had one go along with the wiring in the box.
Last edited by double06; Feb 13, 2021 at 09:34 AM.
Quick update...it ended up being the connector that typically burns up. Specifically it was the middle, ground wire that seems to have been the culprit. I cut and spliced that wire and the fans have been working great now. Let this be a lesson learned...even if the connector is not obviously melted, it can still be the issue.
Dano, seriously thank you for all the info. If my stock pwm does ever fail I will know exactly what to do to upgrade it.
Quick update...it ended up being the connector that typically burns up. Specifically it was the middle, ground wire that seems to have been the culprit. I cut and spliced that wire and the fans have been working great now. Let this be a lesson learned...even if the connector is not obviously melted, it can still be the issue.
Dano, seriously thank you for all the info. If my stock pwm does ever fail I will know exactly what to do to upgrade it.
No worries, and like to think of the up line coupler as the slow blow fuse when it does a melt down. Hence in OEM, it will melt, before you do a melt down of the PWM and it connector next.
So with the cut and spice of the middle connector now hard wired, either fan running a lot more due to change in tune settings, or just the new fan pulling more amperage that the PWM and it wire gauging was designed for, here is going to be your next "bundle of Joy" shortly instead.
Cooling Fan Issues
