Ice forms appropriately (when at or below 0C and within clouds) but won’t clear if the deice pump is just set to Norm. It has to be set to MAX and also selecting max flow to Windshield to clear the windshield or airframe to restore handling. Anything less will not clear the ice or slow it from forming as far as I can tell.
This will occur in very light icing conditions such as 0c or -1C and just clouds. Extreme weather is not required.