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High current wires next to sensor wires

EFI Wiring Fundamentals

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Discussion and questions related to the course Motorsport Wiring Fundamentals

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I'm laying out a harness for a modified street car, bringing a 1990 Miata into the 21st century. I'm adding a bunch of sensors (IAT, Oil temp, Oil pressure) bundled with some high-current parts. The largest is a radiator fan circuit designed for 50A max. Is this alright or should I try to route them such that there isn't interference? IAT and my Wideband O2 sensor are my biggest concerns. Thanks.

It would be best to route them separately - the problem isn't the actual current, but that every time it's turned on, and off, there is a change in the magnetic field that can cause a spike in the adjacent wires. Those senders shouldn't be too sensitive, unlike crank and cam' ones, but still...

It the fan uses PWM speed control, even more care would be wise.

Oh, don't forget the ground/earth side, too.

Thanks for the input, that's exactly what I was afraid of.

The fan is PWM. is the concern there that you wouldn't see a jump in the data log, just a variable offset that isn't obvious?

Not so much a variable offset, if I understand your question, more a slight voltage spike, either way, as the circuit is switched on and off.

It may not affect those sensors, but something like a crank or can trigger, that relys on voltage fluctuations from the senders, may have problems with the ECU reading the spikes as false signals. It may be unlikely, but why take a chance.

Would this apply to alternator wires also. I am adding a pdm and trying to eliminate the fuse box and relays in the engine compartment. The stock harness runs the alternator wires in a separate harness than the engine controls. I will use shielded cable for the cam position sensor and the injector wires but will I have an issue combining the alternator wires into the same wire harness as the engine controls?

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