I was referring to the gold posts in the position marked "E0" on the edge of the Azteeg board itself. The pair of wires from your extruder thermistor should be plugged in there.
See attached image. The purple arrow at the bottom edge of the image points to where the E0 connector plugs into the board. Pull this connector up about 2mm, without disconnecting it. With the Azteeg controller powered down, reach under the connector with the ohmmeter probes and measure the resistance between the two gold posts. This is the easiest way to measure the resistance of the device that is connected there (which should be your extruder thermistor).
If this resistance really does measure 18 ohms, then you probably have something other than your thermistor plugged in there. This would explain why you get an error message when you run the printer.
If you have the wrong thing plugged in there, then swapping to a different Azteeg controller will not help you! You have to get the wiring correct.
This is a different issue:
If all four of your driver boards are labelled "SD82A", then I think you need to have all three microstepper selection jumpers installed under each driver board. Whosawhatsis should confirm that this is correct for your configuration, and that you are using the correct firmware for that configuration.