  The doubly charged Higgs bosons $H^{\pm\pm}$ searches at the Large Hadron
Collider (LHC) have been studied extensively and strong bound is available for
$H^{\pm\pm}$ dominantly decaying into a pair of same-sign di-leptons. In this
paper we point out that there is a large cavity in the light $H^{\pm\pm}$ mass
region left unexcluded. In particular, $H^{\pm\pm}$ can dominantly decay into
$WW$ or $WW^*$ (For instance, in the type-II seesaw mechanism the triplet
acquires a vacuum expectation value around 1 GeV.), and then it is found that
$H^{\pm\pm}$ with mass even below $2m_W$ remains untouched by the current
collider searches. Searching for such a $H^{\pm\pm}$ at the LHC is the topic of
this paper. We perform detailed signal and background simulation, especially
including the non-prompt $t\bar{t}$ background which is the dominant one
nevertheless ignored before. We show that such $H^{\pm\pm}$ should be
observable at the 14 TeV LHC with 10-30 fb$^{-1}$ integrated luminosity.
