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Super Road Rocket Pilot
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Discussion Starter #1
I know this has been discussed many many many times in the past, how to lower the operating temperature of the fans to make them come on sooner and cool the engine and make it run at a lower operating temperature. There have always been only one way discussed to do it, change the programming in the computer that controls the turn on temperature either with a handheld programmer for $100 or have a company tune the computer for several hundred.

What is never discussed (at least I never ran across it) is the simple idea of installing an adjustable aftermarket cooling controller. Basically just bypassing the electronic command signal from the computer with an adjustable analog controller that is widely available across the world.

Looking at the schematics for a 2006 (earlier models seem the same) it looks simple enough. Personally, if I did it I would just remove the low speed fan setting and use the high speed only. The low speed circuit uses the internal resistor in the fan and it commonly goes bad with prolonged use, just connect the components to the high side.

The relay and wiring is all there, all you need to do is purchase an inexpensive 10 amp automotive temp controller for $20-$30, remove power and -

1. Disable the dark green wire for low speed control by cutting at the bottom side of the schematic between the relay and computer and terminate both ends. Or, I guess you could simply remove the #1 relay......
2. Cut the dark blue wire for high speed ground, terminate the computer side, connect relay side to ground.
3. Use the pink wire from Ignition at the top side of the schematic as the power wire for the controller. The other side of the pink wire is now going to be the signal wire to turn on the fan relay #2, wire it up accordingly to the controller.
4. Connect the temp sensor probe to the radiator
5. Once everything is connected, dial in your desired turn on temperature at controller, done! You will now have high speed fan movement when the fan turns on at your temperature setting and you will be bypassing the problematic resistor in the OEM fan.

I know the SE auxiliary fan has a controller, this would be simpler to install since everything is already there, all you are doing is splicing into or cutting existing wiring to prevent the relay signal from the computer from coming on at a higher temp. Doing this will not affect any computer controls since all the sensors are still sensing data and compensating for any change in operating conditions.

This sure seems like a better idea to control the fan if all you are looking to do is modify the turn on temperature.


 

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2004 Slingshot Yellow
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Would have to make sure this don't defeat the signal from the A/C compressor to turn on the high speed.
That may be a discrete signal from the ECM instead of a hard wired relay like the old days.
Here my A/C runs 9 months of the year!
Greg
 

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@Dragon2U - good thought but it would defeat the ability of the cooling fan to come on with AC operation (high side pressure). I know the Radiator temperature would then go up and turn on fan but would it effect AC performance?

This would also cause the Check engine light to come on and codes P0480 and/or P0481 DTCs to be set.

The computer monitors the ground control circuit drivers for the two relays. It expects to see close to 12 volts on this circuit when relay is commanded off and close to 0 volts when relay is commanded on. If either of these is not correct it will set one of these codes. P0480 relay #1 (low speed) P0481 relay #2 (high speed).

You could wire in one of these add-on devices however it would require its own relay and you would then splice into (not instead of) the high speed fan motor feed wire. There would then be two methods to turn on high speed fan. The add on sensor and/or the stock circuit wiring. The stock circuitry is rated at 60 amps - therefore the add on circuitry would have to be a least the same.
 

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Super Road Rocket Pilot
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Discussion Starter #5 (Edited)
Would have to make sure this don't defeat the signal from the A/C compressor to turn on the high speed.

Greg
Hmmmmm, AC performance. Not sure of the degradation due to no fan. I think it would be minimal since the idea is to run the fan on at a 190 to 200 turn on temp instead of 226 but it is a good point. Maybe another relay??


@Dragon2U - good thought but it would defeat the ability of the cooling fan to come on with AC operation (high side pressure). I know the Radiator temperature would then go up and turn on fan but would it effect AC performance?

This would also cause the Check engine light to come on and codes P0480 and/or P0481 DTCs to be set.

The computer monitors the ground control circuit drivers for the two relays. It expects to see close to 12 volts on this circuit when relay is commanded off and close to 0 volts when relay is commanded on. If either of these is not correct it will set one of these codes. P0480 relay #1 (low speed) P0481 relay #2 (high speed).

You could wire in one of these add-on devices however it would require its own relay and you would then splice into (not instead of) the high speed fan motor feed wire. There would then be two methods to turn on high speed fan. The add on sensor and/or the stock circuit wiring. The stock circuitry is rated at 60 amps - therefore the add on circuitry would have to be a least the same.
Sure, the AC system might have a very very slight affect for a short time until things warmed up. With the AC "on" the fan should not take long at all. You are still going to have air flow while driving, just not when stopped.

Hmmmmmm, are you sure a code would be set due to no connection to the relay? I did not think there was a discrete for that. If the computer is looking for a signal through the low speed relay you could just disable the low speed power to the fan line and let the low speed circuit function as is but without power to fan. This would take care of the low speed code. And since the fan will be turned on sooner than the OEM specs, I would suspect that the high speed error would never occur since the cooling would already be active and it would never send the signal unless there was an overtemp which would mean a bad fan anyway. Or would you need to connect the high speed sense wire to a ground?

My concept would connect to existing wiring and relays, all you would need is the controller and temp sensor.

Or you could just get the external fan sold by Mike @ S/E....
It comes with the controller....

Frank....
Yes, the $250 aux fan includes a fan, relay and controller, but my thought process was to create a cheaper ($20) alternative to programming or adding more expensive equipment. Adding the aux fan will not change things the same as programming with a $200 handheld programmer or a $600 "pro" tune.


All good points for sure. The concept might work or need a little tweaking, just thinking out of the box to provide a inexpensive alternate idea...... :smile2:
 

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Why not just get a programmer? I have Diablo sport u71-93 tuner. I uninstall GM tune & install a 87 octane tune. Do not run Horsepower tune when cruising. Fans come on sooner & cut off when desired temperature is reached. No cutting into wiring & works with current wiring & resistors. Yes I have Simple engineering fan. Have not had a problem with my SSR over heating. I also use the orange coolant & have bleed all the air out of cooling. My first trip to Fort St Down river cruise. Temperature was over 210 degrees. I went looking for a alternative since I have not been well? Accepted by car people here in Toledo Ohio. Found Diablo sport tuner at 4 wheel diversified in Maumee Ohio. I went to Telegraph Rd & Woodward Ave Dream cruise in Michigan with no over heating problem. Yes I do still run A/C with snowflake tuned on. Blowing cold air across my feet is the way to go. Minimal purchase of $200 & I can always go back to factory tune when I take my 2004 SSR for service. GM will not work on your SSR if wiring is altered.
 

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Hmmmmm, AC performance. Not sure of the degradation due to no fan. I think it would be minimal since the idea is to run the fan on at a 190 to 200 turn on temp instead of 226 but it is a good point. Maybe another relay??




Sure, the AC system might have a very very slight affect for a short time until things warmed up. With the AC "on" the fan should not take long at all. You are still going to have air flow while driving, just not when stopped.

Hmmmmmm, are you sure a code would be set due to no connection to the relay? I did not think there was a discrete for that. If the computer is looking for a signal through the low speed relay you could just disable the low speed power to the fan line and let the low speed circuit function as is but without power to fan. This would take care of the low speed code. And since the fan will be turned on sooner than the OEM specs, I would suspect that the high speed error would never occur since the cooling would already be active and it would never send the signal unless there was an overtemp which would mean a bad fan anyway. Or would you need to connect the high speed sense wire to a ground?
:
I would be concerned about high side AC pressures with cooling fan not coming on except with radiator temp.

Yes I am sure about codes. The computer can only monitor the circuit it controls. The relay coil circuit (direct output). It can not monitor the high current fan feed circuit (indirect output). So even removing a relay will set a code but unplugging or removing the fan WILL NOT set a code.
Please read attached copied from service manual.
 

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Daily Driver
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Or if you have a hard time with pdf documents...

DTC P0480 or P0481
Circuit Description

The following DTCs are for the cooling fan relay control circuits controlled by the powertrain control module (PCM):

• DTC P0480-low speed cooling fan relay control circuit

• DTC P0481-high speed cooling fan relay control circuit Ignition 1 voltage is supplied to the cooling fan 1 relay from the IGN E fuse. The PCM controls the low speed cooling fan relay by grounding the low speed cooling fan relay control circuit.

Ignition 1 voltage is supplied to the cooling fan 2 relay from the IGN E fuse. The PCM controls the low speed cooling fan relay by grounding the low speed cooling fan relay control circuit. The PCM grounds the cooling fan relay control circuits through an internal solid state device called a driver. The primary function of the driver is to supply the ground for the component being controlled. Each driver has a fault line that is monitored by the PCM. When the PCM is commanding a component on, the voltage potential of the control circuit should be low, near 0 volts. When the PCM is commanding the control circuit to a component off, the voltage potential of the circuit should be high, near battery voltage. If the fault detection circuit senses a voltage other than what is expected, the DTC will set.

COOLING Fan Operation

The low speed cooling fan is commanded ON when the coolant temperature reaches 108°C (226°F) . It is turned OFF if the coolant temperature lowers to 104°C (219°F). The high speed cooling fan is commanded ON when the coolant temperature reaches 113°C (235°F). It is turned OFF if the coolant temperature lowers to 108°C (226°F). When the A/C is ON and the coolant temperature reaches 85°C (185°F) , the low speed cooling fan will be turned ON at vehicle speeds less than 56 km/h (35 mph).

If engine temperatures are to low for cooling fan operation the PCM will command the cooling fans to cool the A/C condenser. The low speed cooling fan will commanded on at 1379 kPa (200 psi) . Then commanded off at 1034 kPa (150 psi). The high speed cooling fan will be commanded on at 1586 kPa (230 psi). Then commanded off at 1482 kPa (215 psi).
 

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I would be concerned about high side AC pressures with cooling fan not coming on except with radiator temp.
COOLING Fan Operation

The low speed cooling fan is commanded ON when the coolant temperature reaches 108°C (226°F) . It is turned OFF if the coolant temperature lowers to 104°C (219°F). The high speed cooling fan is commanded ON when the coolant temperature reaches 113°C (235°F). It is turned OFF if the coolant temperature lowers to 108°C (226°F). When the A/C is ON and the coolant temperature reaches 85°C (185°F) , the low speed cooling fan will be turned ON at vehicle speeds less than 56 km/h (35 mph).

If engine temperatures are to low for cooling fan operation the PCM will command the cooling fans to cool the A/C condenser. The low speed cooling fan will commanded on at 1379 kPa (200 psi) . Then commanded off at 1034 kPa (150 psi). The high speed cooling fan will be commanded on at 1586 kPa (230 psi). Then commanded off at 1482 kPa (215 psi).
Autoprof is right on target here and Bruce is supplying the exact reasoning.

The Air Conditioning system depends on the computer control of both low speed and high speed fan to provide "normal" AC operation. If the system does not have a low speed, the cooling fan will cycle in high speed.

Clearly, the simplest method of causing the cooling fan to run is to have the compressor running. This will provide consistent airflow across the condenser and the radiator. Net result is that the water temp will be at the thermostat set point all the time.....

Regards,

Mike
 

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Super Road Rocket Pilot
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Discussion Starter #10 (Edited)
Mike,
That would be why everyone likes to get the fan turn on at around the 190 200, to keep the fans on all the time. This mod would likely do that as well if the user set the temp at around 190, it would basically be at the set point of the water thermostat opening set point of 187 and should keep the truck at the 195 200 mark. Having the fan constantly going low to high to off to high to low, etc during a driving cycle has got to be hard on the fans and other associated components. Keeping the system on nearly all the time makes people happier than seeing 235-240 on the gauge even though that is what the engineers like.


Thanks Bruce.
The highlighted areas you identified in red show that if only one relay was used only as a temp circuit, the temp turn on difference difference would likely be about 5 degrees (185 vs 190) in a running configuration below 35 mph. I say 190 because that is where I set my Superchip programmer to command fan at high speed and I would usually run 200 degrees at that setting.

Driving over the 35 MPH and everything would act normally. I believe that any AC performance for the 5 degree difference at below the 35 mph would be minimal and rarely seen. BUT...... the other condition is the AC pressures which were not highlighted. The AC likes to have the fan on to cool the coils when it is extracting heat from the cabin.

Everyone here knows that the OEM VW fan pulls very little air due to no shroud. I really wonder what AC performance loss there would be by not having the OEM fan come on when the AC system is on recirculate, forcing the engine fan on before the engine is at coolant flow temp. And how often is this circumstance going to happen with the truck at below 190 degrees with an OEM 190 thermostat installed? Seriously, I think it would be only be a matter of minutes before things would operate as normal. Unless you were in the snow belt, but then there would be no need for the fan to blow cold air.

But to solve any question about the AC interface and performance .......
1. Leaving the low speed circuit connected and deleting the power wire to the low speed side fan to prevent the code but disallow operation.
2. Disable the high speed fan relay and installing two 10 amp capable relays in an "either/or" configuration that would control the factory 60 amp relay in the computers place. One relay for the adjustable radiator thermistor control and one relay to sense for the AC compressor power on. Thus, any time the AC system is on, or the engine temp is above your set point (190 ish) the fan would run at high speed.


Again, I know it is super easy just to go out and get a cheap programmer (like I do) and set the turn on temp yourself and bypass all this BS. But, this is just a "what if" exersize. If someone wanted to control the fan operation on the cheap without a programmer I think this alternative would work well. The thing I hate is that everything is being controlled by a computer nowadays. Headlights, turn signals, door locks, wipers, steering, etc..... and soon they will be driving us around without our intervention. It's a plot I tell ya, the machines are taking over :glol

Being an old school aviation electronic technician I guess I have too much time on my hands lately and wonder if there is an alternate way. Maybe not a better way, but a suitable alternative to the mainstream thought process.
 

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One of the SoCal Nuts
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I guess I have too much time on my hands lately and wonder if there is an alternate way. Maybe not a better way, but a suitable alternative to the mainstream thought process.
Isn't that the kind of thinking that got us into this situation in the first place 25 years or so ago?:jester
 

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Being an old school aviation electronic technician I guess I have too much time on my hands lately and wonder if there is an alternate way. Maybe not a better way, but a suitable alternative to the mainstream thought process.
Mike,

I have a similar background in aviation, electronics, instrumentation and control systems...... we should compare notes some time over a couple glasses of iced tea.... for certain, there is always more than one way to get a job done..

I have a few basic requirements for electrical/electronics modifications, whether they are in a business jet or a pickup truck. Some of the more significant ones are:
  • Avoid modification of the production wiring.
  • Avoid adding failure modes to the system being modified.
  • Provide modifications that can be done by the "least common denominator" installer.
  • Keep the installation simple.
  • Provide clear documentation.
  • Make it easily reversible to original configuration.
  • Avoid impact to other systems.
I'm in Las Vegas right now and running out the door to get to SEMA today. Please give me a call on my cell when you have some time. I'd like to share some of my plans for adding to the control system........ 480-225-2123 If I don't answer, please leave me a quick message and I'll return your call when I can...

My best,

Mike
 
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