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Piggy-backing electronic gauge sensors for ECU

Practical Motorsport Wiring - Club Level

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Hi all,

I have several autometer electronic ultra-lite (stepper motor) gauges installed in the race car. I am converting carbs to EFI and have purchased a Haltech 750.

It would be convenient to use the existing electronic gauge sensors for the ECU. I called AutoMeter, and they said the gauges do not have a signal repeater. They said the 2-wire sensors (temp) were resistance variable, and the three wire (pressure) were voltage variable.

is there a way I can splice the signal to the ECU?


The Pressure sensors you can usually get away with splicing to two different devices, but Temp sensors don't always work as you are adding extra resistance into the circuit. You would need to wire the Temp sensor into a AV input on the ECU so that there is no other pull up to 5V being added in, as happens with a AT input (they are wired to the 5V supply through a 1k ohm pull up typically) and confirm that the temperature being reported doesn't change with the ECU connected.

I would rather run dedicated sensors for the ECU.

Thank you! This was very helpful. I will double-up on my coolant temp sensors and splice my fuel/oil pressure sensors for engine protection.

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