What causes cooling fans to come on too early?

[randy]

It will be in your tune. Do you have HP tuners?

[72Z/28]

Originally Posted by randy

It will be in your tune. Do you have HP tuners?

Unfortunately I do not have an HP tuner.

I am a bit confused he could not recognize the fan operating temperatures from the tune even though they are wired from the ECU.

[andre68]

Are you using an OEM ECU, or an aftermarket Holley, etc? I am not a tuner of LS engines, so I can't guide you on what scan tool/computer software to use. But I would invest in one so you can check things like this yourself. I can't speak for what your tuner saw on his software. I'd call him and confirm or find a new tuner....you need to see what temp the ECU is looking for when opening the fans. Seeing that you have an LS, the ECU will be relying on a temp sensor located on the driver side head. Unfortunately, an infrared gun on a hose will not match the temperature the ECU is seeing when it turns on your fans.

BTW, when you say overflow tank, do you mean an expansion tank (that has a pressurized cap?) or a recovery tank? (regular threaded cap)
My method will work wherever the pressurized cap is, whether its the radiator or expansion tank.

A recovery tank simply holds discharged coolant from the pressure relief when the coolant is expanding.....this tank will have a simple threaded cap (no pressure rating). If this is the tank you have.....you'll notice that the hose connecting to this tank will be connected to the filler neck of the pressurized cap (wherever that is....radiator or expansion tank). That hole is so close to the opening of the filler neck that the coolant will overflow the open filler neck wayy before it starts filling up the recovery tank.

Here is some info from canton racing: http://blog.cantonracingproducts.com...on_vs_recovery

Assuming the recovery tank is at the correct level and sits above the pressurized cap, no air pockets will be trapped in there.

And just to knock out another obvious, check if your A/C is on (if you have it). The fans may come on sooner when the climate control is on.

[randy]

if you are located near dallas i could pull your tune file quick and tell you.

if you are using HP tuners or can get access its under systems, fans. Lots of fan options there. You dont need to buy credits to read the tune.

[72Z/28]

Originally Posted by andre68

Are you using an OEM ECU, or an aftermarket Holley, etc? I am not a tuner of LS engines, so I can't guide you on what scan tool/computer software to use. But I would invest in one so you can check things like this yourself. I can't speak for what your tuner saw on his software. I'd call him and confirm or find a new tuner....you need to see what temp the ECU is looking for when opening the fans. Seeing that you have an LS, the ECU will be relying on a temp sensor located on the driver side head. Unfortunately, an infrared gun on a hose will not match the temperature the ECU is seeing when it turns on your fans.

BTW, when you say overflow tank, do you mean an expansion tank (that has a pressurized cap?) or a recovery tank? (regular threaded cap)
My method will work wherever the pressurized cap is, whether its the radiator or expansion tank.

A recovery tank simply holds discharged coolant from the pressure relief when the coolant is expanding.....this tank will have a simple threaded cap (no pressure rating). If this is the tank you have.....you'll notice that the hose connecting to this tank will be connected to the filler neck of the pressurized cap (wherever that is....radiator or expansion tank). That hole is so close to the opening of the filler neck that the coolant will overflow the open filler neck wayy before it starts filling up the recovery tank.

Here is some info from canton racing: http://blog.cantonracingproducts.com...on_vs_recovery

Assuming the recovery tank is at the correct level and sits above the pressurized cap, no air pockets will be trapped in there.

And just to knock out another obvious, check if your A/C is on (if you have it). The fans may come on sooner when the climate control is on.

I have OEM ECU with blue and red connectors. Dark green wire (pin 42) and Dark Blue wire (pin 33). Both going from ECU or PCM to fan relays.

Both fans come on as soon as turn on the AC even with cold engine.

By the way, I have a recovery tank not the expansion tank

I have found so many threads in LS1Tech regarding wiring cooling fans and AC with binary or trinary switches. Unfortunately, I could not find a clear schematic that shows wiring trinary switches with dual fans and compressor.

I am just sick of going through the cooling fans wiring, relays as I have to trace all the crapy wiring done by the stupid electrician. This may require dropping the vintage air evaporator just to trace one stupid wire.

Just do not feel like doing this as I have recently rearranged the big mess on the dash wiring, and I still cannot figure out why the stupid tach and speedometer on classic instruments do not work.

[dhutton]

Originally Posted by 72Z/28

I have OEM ECU with blue and red connectors. Dark green wire (pin 42) and Dark Blue wire (pin 33). Both going from ECU or PCM to fan relays.

Both fans come on as soon as turn on the AC even with cold engine.

By the way, I have a recovery tank not the expansion tank

I have found so many threads in LS1Tech regarding wiring cooling fans and AC with binary or trinary switches. Unfortunately, I could not find a clear schematic that shows wiring trinary switches with dual fans and compressor.

I am just sick of going through the cooling fans wiring, relays as I have to trace all the crapy wiring done by the stupid electrician. This may require dropping the vintage air evaporator just to trace one stupid wire.

Just do not feel like doing this as I have recently rearranged the big mess on the dash wiring, and I still cannot figure out why the stupid tach and speedometer on classic instruments do not work.

At least one fan should come on when you turn on the AC if you are using a binary switch. It has nothing to do with the engine temperature.

Don

[randy]

located near dallas at all?

[72Z/28]

Originally Posted by randy

located near dallas at all?

Thanks Randy for the offer, well appreciated.
Unfortunately I do not live in the USA.

I have drown a rough schematic of cooling fans wiring along with compressor and Binary Switch.

I am going to share the link soon to my instagram, and hopefully someone could go through the schematic and correlate with how the fans are operating now based on information given in my previous posts