Depends on the definition of "crime" in that state.
In WI, a simple equipment violation like that would not be a crime, as the only punishment possible is a fine.
Almost.
Terry says that
if an officer has stopped (detained) someone
and has reason to believe [RAS] that the person is
both armed
and dangerous
then s/he may search (pat down) the person's clothing searching for (& removing) possible weapons for the duration of the arrest (stop).
"Where a reasonably prudent officer is warranted in the circumstances of a given case in believing that his safety or that of others is endangered, he may make a reasonable search for weapons of the person believed by him to be armed and dangerous regardless of whether he has probable cause to arrest that individual for crime or the absolute certainty that the individual is armed."
http://www.law.cornell.edu/supct/html/historics/USSC_CR_0392_0001_ZS.html
Note the conjunction: armed
and dangerous. Have to satisfy both parts.
And simply being armed is not evidence of being dangerous.