Spartan 3 overheats immediately


My brand new spartan3 that I just installed always keeps blinking at about 2 blinks a second.
This is with a brand new sensor you provided.

It does it immediately after cranking when engine is cold and after it has been running for a few minutes.
The car is a 90hp Miata and I don’t believe that it would instantly overheat the sensor.

The AFR readings are also stuck at 13.3.

Connection wise everything looks good, the controller to megasquirt works fine. I have verified that the controller gets power and

Any idea what’s wrong?


Is this forum still active?

I got a response same day as I sent an email, but got stuck in my spam.

Hi Turbogrill or Toalan

Can you provide any details on the fix for this?

I’m experiencing a very similar behavior with a new setup… the red light immediately flashes quickly. My sensor’s heater circuit seems to measure properly with a multimeter.


During the initial heatup it is normal for the sensor to show too hot for a few seconds and then quickly settle to the correct temperature. After the initial heatup the LED should not blink.