Sharing Water Temp Sensor

For discussing how to choose sensors and create a wiring harness for all Bowling and Grippo versions of the MegaSquirt® EFI controller.
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nqtraderman
MegaSquirt Newbie
Posts: 5
Joined: Sun Jan 18, 2009 4:49 am

Sharing Water Temp Sensor

Post by nqtraderman »

The attached diag shows the temperature sensor wiring on my Jag. Basically the +12v is regulated down to +10v then fed through the water temperature sensor and onto the temperature gauge. The sensor is the 1-wire type but I can swap that to a modern 2-wire sensor for better grounding.

Can I splice into this wire and use this same sensor as the Coolant sensor for the MS ?
thanks
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Matt Cramer
Super Squirter
Posts: 2951
Joined: Sat Jul 03, 2004 11:35 am

Re: Sharing Water Temp Sensor

Post by Matt Cramer »

That sounds like it's a thermal gauge, and it's unlikely you would be able to split the signal with the MS. For this to work, you would need the voltage between the gauge and the sensor to never be above 5 volts, you would need the instrument voltage regulator to be a solid state one that delivers a steady voltage rather than a mechanical unit that is really putting out a square wave, and you would need a high enough resistance inside the gauge to result in significant voltage changes at the junction between the gauge and sensor. Most thermal gauges fail to meet at least one of these rules.
nqtraderman
MegaSquirt Newbie
Posts: 5
Joined: Sun Jan 18, 2009 4:49 am

Re: Sharing Water Temp Sensor

Post by nqtraderman »

Thank you Matt, I'll go with a seperate sensor .
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