In all my old F-bodies I could hard wire one of the fans to run when the car was off. Any tricks like this for the vett?

Going to the track tomorrow and it's going to be hot, want to cool the car down as much as possible between runs.

Thanks!
Jason

 

yeah, someone a while ago did exactly that and reported that he experience no issus / cel. i don't recall the user name, do a search you might be able to find it. good luck at the track.

 

The Corvette has a single fan, its speed is varied by the ECM via a PWM waveform (basically, the ECM pulses the voltage on and off very rapidly and varies the ratio of the time the voltage is on to the time it is off to control the fan's speed). Maximum on time is 90%. In other words, the average voltage fed to the fan when fan speed is maximum is 90% of battery voltage (minus about 0.2 volt for switching transistor saturation), or 12.22 volts. Lower fan speeds are achieved by reducing the ratio of voltage on time to off time in the waveform, thus resulting in a lower average voltage at the fan.

So you have to be careful when hotwiring the fan, or you can damage the FCM (which is just a transistor switch pulsed on and off by the ECM). The safest way to wire it would be to use diode steering to eliminate the possibility of backfeeding the FCM directly with battery voltage, which could fry it (and possibly the ECM too). Basically, you configure a pair of diodes as an OR gate, with one side fed from the battery by a switch, and the other side fed by the FCM as normal. The output of the OR gate feeds the fan. This is how a RV dual battery isolator works too (but the diodes in a dual battery isolator are configured opposite polarity from what you need here, so you can't just use one of those, you'd have to wire it up with two individual power diodes). Wired right, this is foolproof, and can't damage the FCM.

Another lower tech method is to just be sure you disconnect the FCM leads to the fan whenever you connect the fan directly to the battery. A DPDT switch could be used to do that. Fan negative is the black wire connected to pin 1 of the FCM. Fan positive is the red wire connected to FCM pin 4. Just be sure the FCM isn't trying to drive the fan when you throw the switch, the resulting transient could blow the FCM. In other words, only throw the switch when the fan is stopped.

The highest tech way to achieve your goal is to reprogram the ECM to run the fan until coolant temperature reaches a desired value. Stock, the ECM won't run the fan with the engine off unless coolant temperature is over 235 degrees (or A/C head pressure is above 249 PSI). But this can be reprogrammed to any temperature you desire.

 

Great info! You da MAN!!

 

http://forums.corvetteforum.com/show....php?t=1345426

here you go with all the instructions / how to. good luck.

 

Wiring it that way is a bit risky. Without using diode steering, there's a possibility the transient when the switch is thrown will damage the FCM. I'd also note that if you're doing this for cool down between rounds at the track, an underhood location for the switch would be fine, thus avoiding the necessity of penetrating the firewall.

 

just by the fan switch from cartek comes on at start to let you know its working then at 181 with 160 therm in hot weather like this heeps my temps at 175-180 om starting line well worth the money plus cool on road

 

Ive given thought to having a manual toggle switch located in the cabin (hidden away in case i have to take the car in for GM warranty service) to run the fan at full speed especially when the A/C is on. I find it somewhat annoying listening to the fan winding up then slowing down when im slow driving or at a stop light. Im going to use a s.p.d.t relay mounted right at the box for the Fan so when i throw the toggle, i deliver full battery voltage to the motor and at the same time interrupt the signal from the ECM/fan box. Ill cover the relay terminals with some liquid rubberized sealant in case water gets splashed up on it. I think the A/C's Condensor will get cooled more due to higher airflow across it which should make the Cooling work even better ; plus, engine temps/oil temps can be kept reasonable on very very hot days.

 

The beauty of owning it is that you can do what you like with it - mod it to please your needs.

However, on this one, I am not sure the benefit outweighs the downside of extra running of the fan for time and voltages higher than designed for, and therefore possible premature wearout of the fan motor.

Something tells me: "Don't touch the fan:"

 

I had the fan temp turn on temp lowered with HP tuner. I have not raced the C6 enough to give you any info on how it is working. I still need to install a 160 thermostat. My tuner was shipped the wrong one so I am waiting to run back up there and have them put it on.

With a 160 thermostat and lowered fan settings in my C5 I could almost always launch at 180. Don't want to launch any cooler than that with a LS1 anyway. It starts to slow up any cooler than 180. I found 180-190 to be the best temp for qtr mile performance in my C5, plan to try same in C6.