V1 Radiator Fan Wires

[averageJOEschmo]

I'm building a Goblin A/T, which means my radiator is in the back and I have two fans. Because the radiator is in the back, I did not need to extend the fan wire to the front and my plan was to connect directly to the existing fan wires. I want to make sure I'm doing this right because don't know this electrical stuff at all.

In the A/T build video, @Lonny uses 3 wires to connect the two fans:

From the stock wiring diagram, I am making the assumption that they are the gray wire (A11) and the light blue wire (F10) coming from the black multi plug in the engine fuse box, and a ground:

So I'm thinking this is how Lonny wired it (option 1):

Or would it be better to wire it like this, splitting the gray wire and cutting the light blue (option 2):

Or because it seems the light blue wire was used in the old videos to extend the fan wire:

Should I wire it like this, splitting the light blue wire and cutting the gray (option 3):

 

[Desert Sasqwatch]

The original Cobalt wire diagram is set up for operating a 2 speed fan with the two relays - Fan 1 and Fan 2. The Fan 1 light blue wire feeds a resistor to lower the voltage to feed the fan for low speed thru the yellow wire. The fan high speed is directly fed by the gray wire from Fan 2 relay.

Since you have 2 cooling fans on the radiator, I would recommend wiring per your option 1 drawing. You still retain the temperature control for operating one fan for 'normal' temperatures and kick in the second fan for higher operating temperatures. My best guess is Lonny would also follow this same logic to use these same parameters.

 

[Gtstorey]

Just to be clear, the later models don’t follow the above as far as fan type and wiring. They use a 3 relay system and 2 single speed fans that swaps the fans from high and low by running them in parallel or series.

 

[Desert Sasqwatch]

To be clear, the schematics for the 2006 2.4 supplied in the first post align with your donor?

 

[averageJOEschmo]

To be clear, the schematics for the 2006 2.4 supplied in the first post align with your donor?

Yep, my donor is a 2006 Naturally Asperated 2.4L Automatic

 

[Desert Sasqwatch]

So the options you described in your original question are valid and the wiring is dependent upon 2 relays - as per the 2006 schematics. Hopefully the comments about later models is not confusing this item?

 

[averageJOEschmo]

I guess if Lonny used a later model then maybe that would explain the 3 wires? Honestly this wiring stuff is all confusing...

This might be a dumb question but if I go with option one, does that mean the fans are only running on 6 volts?

 

[Desert Sasqwatch]

Feeding the Fan 1 relay light blue wire from the BCM F10 directly to one of the new radiator fans will bypass the fan resistor yellow wire that has the reduced voltage (which would probably be between 6-9 volts). This will power the new fan at full speed with 12 volts from the Fan 1 relay.

Feeding the Fan 2 relay gray wire from BCM A11 provides 12 volts to the other new fan.

 

[averageJOEschmo]

Thank you Sasqwatch!

 

[Joebob]

I would go with Option 3 for 2 reasons. First, since Lonny reviewed the schematics and understands the system better than most, he chose the Blue wire as the safer bet to run the system as the ECU should always demand slow speed more often than high speed. Second, with the original system, there is only 1 motor with the system designed to only power the system one at a time. To me if the ECU wants low, it will power motor 2 in your Option 1 and Motor 1 when the ECU wants high, but not with motor 2. Option 2 would wait until the ECU demands high flow before turning on the fans at all. I think the safest plan is to do Option 3 since you have no natural flow and wire both fans to the blue circuit. The 80 watt fans should pull less than 15 amps total so the single 30 amp fuse should be ok.

Joe

 

[Ross]

To help me figure out the options, I made these tables. I'm with Lonny and Squash on this one.

Stock 2.4L Cobalt

ECU Desired cooling	ECU Dark Green wire	ECU Dark Blue wire	Fan 1 Grey wire	Fan 1 Yellow wire
Low speed fan request	12V	0V	0V	6-9V
High speed fan request	12V	12V	12V	6-9V

Option 1 (Lonny, Squash and my choice)

ECU Desired cooling	ECU Dark Green wire	ECU Dark Blue wire	Fan 1 Grey wire	Fan 2 Lt Blue wire
Low speed fan request	12V	0V	0V	12V
High speed fan request	12V	12V	12V	12V

Option 2

ECU Desired cooling	ECU Dark Green wire	ECU Dark Blue wire	Fan 1 Grey wire	Fan 2 also Grey wire
Low speed fan request	12V	0V	0V	0V
High speed fan request	12V	12V	12V	12V

Option 3

ECU Desired cooling	ECU Dark Green wire	ECU Dark Blue wire	Fan 1 Lt Blue wire	Fan 2 also Lt Blue wire
Low speed fan request	12V	0V	12V	12V
High speed fan request	12V	12V	12V	12V

If you are willing to swap to the LSJ fuse box, you also could follow the LSJ wiring, and get this fan result:

LSJ Option

ECU Desired cooling	ECU Dark Green wire	ECU Dark Blue wire	Fan 1	Fan 2
Low speed fan request	12V	0V	6V	6V
High speed fan request	12V	12V	12V	12V

 

[Desert Sasqwatch]

Keep in mind this is an AT kit build with the radiator in the back. The radiator fans are the airflow source, not airflow through the nose. Having a strong cfm from the fan running on 12 volts - one or both - is probably the best recommendation.

 

[Ross]

Why did Chevy decide to go to the extra expense (3 relays) on the LSJ to run both fans on 6V?
It would have been easier to just wire the 2 fans with 2 relays.

Option 2 might flow more air when the ECU desires a low speed fan, but it also uses twice as much power (wattage), and makes twice as much fan noise according to this thread. Maybe Chevy just wanted quieter fan noise at low speed fan. Both options are the same when the ECU desires a high speed fan.

Or maybe the air flow is better with both fans at 6V. Does the air go in a circle with one fan at 12V and the other at 0V?

Option 2

ECU Desired cooling	ECU Dark Green wire	ECU Dark Blue wire	Fan 1 Grey wire	Fan 2 also Grey wire
Low speed fan request	12V	0V	0V	0V
High speed fan request	12V	12V	12V	12V

LSJ Option

ECU Desired cooling	ECU Dark Green wire	ECU Dark Blue wire	Fan 1	Fan 2
Low speed fan request	12V	0V	6V	6V
High speed fan request	12V	12V	12V	12V

 

[averageJOEschmo]

Thanks for the discussion everyone, I really appreciate all the input and helping me think through this.
I'm starting to lean towards option 3 so both fans are spinning at the same time and that way I get airflow evenly across the whole radiator, even at low demand. The biggest drawback with approach seems to be a higher power consumption but efficiency isn't the primary objective with this build. Does my logic seem sound?

 

[Ross]

Why not go with Option 1?
The ECU is designed to turn on a bit of fan when it needs a little bit of cooling.
The ECU is designed to turn on a lot of fan when it needs a lot of cooling.

Option 3 just goes to full fan right away... even when the ECU only wants a little bit.
Up to you, I was just wondering why Option 3?

PS, I have played with the fan settings in HP Tuners on my LSJ. You can set different temperatures. Not sure about the 2.4L ECU.

 

[averageJOEschmo]

If I'm understanding correctly, option 1 will only control the difference between low and high cooling needs by running one (for low) then two fans (for high). This sound fine and was my original plan, however in low cooling situations, when only one fan is running, the air flow will only be across half the radiator. It might not be a big deal, but I like the idea of even air flow, even if its more than it needs, across the whole radiator rather than having one side be getting cooler while the other is still hot. It seems like this will just cause a temperature differential that could warp or lead to undue stress on the radiator.

Other than a bigger power draw, is there any downside to having a bigger response to a low cooling need?
Would this lead to the system cycling on and off more frequently? And is that a problem?

 

[Ross]

The coolant circulating thru the radiator only drops a few degrees, so the aluminum won't cool down much. The air changes temps a lot, but not the coolant.

My LSJ only uses the fan on hot summer days. The rest of the year it never turns on. But you have a different Ecotec, and may be driving slow on a dirt road, so you might use the fans more than me.
Any of your options will work, and keep the engine cool. The only downside I see is fan noise.

 

[Desert Sasqwatch]

No radiator stress for a temperature difference between sides - which it will have regardless as hotter fluid enters the radiator and leaves several degrees cooler. Having one Fan pulling air on one side of the radiator will have no detrimental effects.

My take on option 1: install Fan 1 at the radiator exit side to get maximum cooling effect when running lower temperatures. Higher temperatures will kick on Fan 2 for the cooling boost for the incoming fluid.

 

[averageJOEschmo]

This is great info guys. So the next question is what direction does the fluid flow through the engine? Hot out the top?

 

[Ross]

The hottest coolant flows out of the head, on the passenger side of the goblin, thru the passenger lower frame.
Then thru the radiator, and back down the drivers side to the thermostat.
The thermostat leads to an aluminum pipe under the exhaust, then to the coolant pump and into the engine block.
Here is a thread on it... probably knows more than I do, as I am just piecing this together today.