Factorio Forums

How to reproduce:

Use the Selector Combinator in Quality Transfer mode with the subsetting 'Select from signal' Input Circuit: Output Circuit: As Expected the uncommon quality is picked and set into the ouput circuit network.

Now remove all signals with normal quality
Input Circuit: Output Circuit: The quality picker is no longer working and does not display the uncommon signal.
This stays true for all quality tiers.
Changing the 'Target Signal' to 'Each' does not work either.
But changing the 'Target Signal' to Uncommon does work. However this only moves the problem to all other quality tiers including 'Normal'

Thanks for the report. This is working correctly:

It is: taking the value of the target signal (normal nuclear fuel) - which is 0 because it doesn't exist - and outputting it with the quality of the best found nuclear fuel (uncommon).

Because the target signal does not exist no value is output.

If this behavior is intended, it’s not intuitive and doesn’t match the description. The tooltip says:
“Searches for the specified signal in the inputs, and picks the highest-quality version of any found signals.”
A reasonable user would expect it to select the input of the given signal type with the highest quality among all available inputs.

Additionally, @Rseding91’s point has a flaw. They said that it “takes the value of the target signal (normal nuclear fuel).” The keyword “normal” implies you can choose among different qualities—and that “normal” quality was selected—but this interface element only lets you pick the signal type (in this case, “nuclear fuel”). You cannot, for example, select “uncommon nuclear fuel.”