Coolant Temp Switch for Gauge

[ebnash]

I just received my Prosport water temp and boost gauges so I will be working on that this weekend. Just curious if anyone has tried tapping into the harness for the coolant temp switch that is already mounted on our engines. This sends a signal to the computer and allows us to read water temp through OBD-II, but I was thinking I may just be able to rob that signal for my electrical gauge.

Has anyone tried this? I am not a fan of splicing into the radiator hose because it is not an accurate reading...

Erik

[treyclash]

not sure about that... maybe someone else will chime in pretty soon. plz post pics of everything mounted and what all u did. this will be something ill b looking into very soon. havent heard anywere about tapping the harness so you may b the first guinne pig.

[fishin53]

If you can figure this out, then you are a god. I wanna figure this out. How about tapping into the wire that connects to warning lights in the gauges?

[ebnash]

Originally Posted by fishin53 If you can figure this out, then you are a god. I wanna figure this out. How about tapping into the wire that connects to warning lights in the gauges?

I am pretty sure that the idiot light is a digital output, so it only triggers when a defined temperature is reached. The coolant temp switch should send an analog signal to the computer, so I am hoping I can just tap into this signal for the gauges.

I may not be doing this this week since I have not received my dual vent pod yet, but when I do, I will take pictures of the whole attempt and post them with a write if it is successful.

Erik

[treyclash]

Originally Posted by ebnash I am pretty sure that the idiot light is a digital output, so it only triggers when a defined temperature is reached. The coolant temp switch should send an analog signal to the computer, so I am hoping I can just tap into this signal for the gauges. I may not be doing this this week since I have not received my dual vent pod yet, but when I do, I will take pictures of the whole attempt and post them with a write if it is successful. Erik

good shit thank you. this is going to be very interesting. i ussually sense major fail but for some reason i see success in your future. like i siad this would b the shit to do.

[SSinstaller]

Originally Posted by ebnash I am pretty sure that the idiot light is a digital output, so it only triggers when a defined temperature is reached. The coolant temp switch should send an analog signal to the computer, so I am hoping I can just tap into this signal for the gauges. I may not be doing this this week since I have not received my dual vent pod yet, but when I do, I will take pictures of the whole attempt and post them with a write if it is successful. Erik

The coolant temp sensor is just a thermistor, connected to the ECM, and the sensor ground, as the temp goes up the resistance goes down... The OEM guage may not be a direct display of the sensor output, but sensor itself is accurate and not just for an on/off idiot light..

You can not connect your aftermarket gauge to the OEM sensor.. You'll just end up with a useless guage, and throw off the ECM as well..

Your gauge should have come with it's own sending unit, you need to use it..

[ebnash]

Originally Posted by SSinstaller The coolant temp sensor is just a thermistor, connected to the ECM, and the sensor ground, as the temp goes up the resistance goes down... The OEM guage may not be a direct display of the sensor output, but sensor itself is accurate and not just for an on/off idiot light.. You can not connect your aftermarket gauge to the OEM sensor.. You'll just end up with a useless guage, and throw off the ECM as well.. Your gauge should have come with it's own sending unit, you need to use it..

I agree with you on how the coolant temp sensor works, but the sending unit that comes with the gauge is the same principal. As temp fluctuates, resistance changes and the gauge resolves that with a needle movement. I believe the temp sensor (electrical, not mechanical) that comes with the gauge operates using the same physics, but it is very possible that the resistance calibration is different between the 2 units. I am also not sure if tapping into that wire will disrupt the signal to the ECU, but this is why I plan to try it and see if it works out. I also have a spare coolant temp sensor is case the wire tap upsets the ECM signal.

Unless someone else has actually attempted this with fail, it is all based on theory, correct? I make no claims of success until it is done.

Hopefully someone speaks up if they have failed with this experiment. My only other option is going to be to buy a spare water outlet and see if I can drill/tap a port for the sensor that comes with the gauge, but this will require draining the coolant to install and I would like to avoid going there unless I have to...

I will do without a dedicated gauge before I splice into a coolant hose to get an inaccurate reading of engine water temp.

[m4tic]

Originally Posted by SSinstaller The coolant temp sensor is just a thermistor, connected to the ECM, and the sensor ground, as the temp goes up the resistance goes down... The OEM guage may not be a direct display of the sensor output, but sensor itself is accurate and not just for an on/off idiot light.. You can not connect your aftermarket gauge to the OEM sensor.. You'll just end up with a useless guage, and throw off the ECM as well.. Your gauge should have come with it's own sending unit, you need to use it..

im thinking there is no OEM gauge for 2010+

[SSinstaller]

Originally Posted by bmorrisj im thinking there is no OEM gauge for 2010+

Did not know that...

Regardless, don't mess with the OEM sending unit...

[rghispanic88]

well, where are the pics?