Radiator cooling fan control

For my LS1 I'm using the 951 radiator and fan.

The wire harness for the LS1 has 2 wires to ground the 2 fan relays. How does the LS1 ECU get the temperature to switch the fans ?

I use the VDO coolant temp sensor connected to PIN 8 – Blue/Yellow to the Water Temp Gauge.

Should I keep the sensor in the radiator to control the fans, and leave the 2 wires from the LS1 ECU.

Thanks for any input.
Engelbert

The LS1 computer uses the temp from the number 1 cylinder as the temp reference that number controls the fan activation. If you do an advanced search for " coolant fans" you can read about the subject. Along the drivers engine compartment side you will see an encased group of wires in a black plastic protective cover with I believe a light blue stripe. Inside the casing is where the temp sensor wires are. They will be red/white and brown/yellow, vifi at the sensor in the radiator.  If you go this route you will be cutting the plug to do this. If you use these wires and connect them to the computer you can use the computer to control the temp at which they activate. Then if you need a place for aux temp gauge the bung could be one. There is a threaded hole on the passenger head #8 cylinder area that could be re tapped for the cars gauge cluster.



If you look in this pic you will see the two wires pulled out of the casing and laying across the engine compartment fender well. Pulling them back obviously gets them closer to the fire wall to be routed back in side the car. a tuning program could be used to change the the activate temp.


So your options after this could be:
1. Use the old radiator temp sensor  bung for auto meter gauge? I did
2. Re tap the passenger head and use that for cars gauge cluster.
the number one cylinder is the one the computer wants for its temp stuff.

Rothaus wrote:For my LS1 I'm using the 951 radiator and fan.

The wire harness for the LS1 has 2 wires to ground the 2 fan relays. How does the LS1 ECU get the temperature to switch the fans ?

I use the VDO coolant temp sensor connected to PIN 8 – Blue/Yellow to the Water Temp Gauge.

Should I keep the sensor in the radiator to control the fans, and leave the 2 wires from the LS1 ECU.

Thanks for any input.
Engelbert

Since you are using the 951 radiator, then just keep it simple and use the stock wiring and relays to control the fans. No need to use the LS1 ecu to control the fans in this case.

Hotrodz of Dallas wrote:

Rothaus wrote:For my LS1 I'm using the 951 radiator and fan.

The wire harness for the LS1 has 2 wires to ground the 2 fan relays. How does the LS1 ECU get the temperature to switch the fans ?

I use the VDO coolant temp sensor connected to PIN 8 – Blue/Yellow to the Water Temp Gauge.

Should I keep the sensor in the radiator to control the fans, and leave the 2 wires from the LS1 ECU.

Thanks for any input.
Engelbert

Since you are using the 951 radiator, then just keep it simple and use the stock wiring and relays to control the fans. No need to use the LS1 ecu to control the fans in this case.

That's what I was thinking. That works for me.

Thanks
Engelbert

I used the original 944 fan control system as well, works fine. But the thermostat is a common failure point so I recommend a fresh stock replacement "while you're in there"...

Rich

Since you are using the 951 radiator, then just keep it simple and use the stock wiring and relays to control the fans. No need to use the LS1 ecu to control the fans in this case.

LOL, That's what I did. Worked like a charm...for 2 weeks. Then the rad temperature sensor failed and nearly stranded me. I made it home by turning the AC on and forcing the fans to run. My fix was to switch it over to LS ECU control.

Gord.