Getting Accurate Factory Temp Gauge with LS swap
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Getting Accurate Factory Temp Gauge with LS swap I've been researching methods of using my factory gauges with my LS3 and spent quite a bit of time by trial and error. Hopefully this thread will help others with this.
Common and easy method is to use the M12x1.5 to 1/2" or 3/8" sender adapter off the port at the back of the passenger side head using your OEM sender.
Trouble is this puts the sending unit probe far way from the water flow so there will be a significant amount of delay and cooling before the sender can see it, for this reason I don't trust it to be accurate.
Next method is to drill and tap your water pump and use the OEM sender. I like this option but you would need an accessible flat location that my Corvette water pump doesn't have.
The last method is to find a sender that fits the M12x1.5 thread and is compatible with your OEM gauge and possibly calibrate the gauge to work with it .
This is the method I came up with.
1), Get a 500 ohm potentiometer and connect it between gauge sensor terminal and battery negative and connect the gauge ground terminal also to battery negative.
2) Connect gauge positive to battery positive.
3) Turn the potentiometer until the gauge needle points to hot, then check the potentiometer ohms resistance at this point, now do the same with pointer at the low side on the gauge, record the ohms.
You will now have the "operating range of your gauge". With mine the needle starts to move above low lowest line at 300 ohms, and hot at 75 ohms.
4) Test your sender by suspending it over a pot of water on a stove with the tip submerged and a thermometer in the water, now check the resistance values at varied temps. Hopefully this matches where you want your gauge to read. If you need to calibrate it you can lower the operating range by adding a resistor in series with the sender, or raise it with a resistor in parallel. You can figure out the resistor needed by testing with that potentiometer as well.
As far as sensors, I found the VDO sensor model 323-092 and the Classic Instruments model SN12MM both to have operating ranges similar to my OEM gauge..
Common and easy method is to use the M12x1.5 to 1/2" or 3/8" sender adapter off the port at the back of the passenger side head using your OEM sender.
Trouble is this puts the sending unit probe far way from the water flow so there will be a significant amount of delay and cooling before the sender can see it, for this reason I don't trust it to be accurate.
Next method is to drill and tap your water pump and use the OEM sender. I like this option but you would need an accessible flat location that my Corvette water pump doesn't have.
The last method is to find a sender that fits the M12x1.5 thread and is compatible with your OEM gauge and possibly calibrate the gauge to work with it .
This is the method I came up with.
1), Get a 500 ohm potentiometer and connect it between gauge sensor terminal and battery negative and connect the gauge ground terminal also to battery negative.
2) Connect gauge positive to battery positive.
3) Turn the potentiometer until the gauge needle points to hot, then check the potentiometer ohms resistance at this point, now do the same with pointer at the low side on the gauge, record the ohms.
You will now have the "operating range of your gauge". With mine the needle starts to move above low lowest line at 300 ohms, and hot at 75 ohms.
4) Test your sender by suspending it over a pot of water on a stove with the tip submerged and a thermometer in the water, now check the resistance values at varied temps. Hopefully this matches where you want your gauge to read. If you need to calibrate it you can lower the operating range by adding a resistor in series with the sender, or raise it with a resistor in parallel. You can figure out the resistor needed by testing with that potentiometer as well.
As far as sensors, I found the VDO sensor model 323-092 and the Classic Instruments model SN12MM both to have operating ranges similar to my OEM gauge..
Last edited by Jimsl78; Today at 03:48 PM.