I just hooked up a brand new Spartan 2 controller to test it, I connected it direct to 12V via the fused red wire, and the white + black wires direct to the battery (-). In free air, the Green wire indicates 4.95V after a short delay, which is what I’d expect. If I start and run the engine, the voltage on the Green wire goes down to about 2.4V, and moves up and down slightly if I change the revs. This seems to indicate that the controller and the sensor are working correctly, and my AFR is too far off of stoic. After about 3 minutes of operation, I noticed that the controller was getting quite hot. Not too hot to touch, but a lot hotter than I’d expect electronics within its safe operating range to get. I suspect that if I left it powered on for 15 minutes, it would get VERY hot. Is this normal?
Are you sure you have a spartan 2 and not a spartan 3?
Yes, I am. This is the one I purchased:
https://www.justraceparts.com.au/spartan-2-wideband-controller-14point7