  We investigate the automorphic spectra of the natural weighted adjacency
operator on the complex arising as a $PGL(3,\mathbb{F}_q[t])$ quotient of
$\widetilde{A}_2$-type building. We prove that the set of non-trivial
approximate eigenvalues $(\lambda^+,\lambda^-)$ of the weighted adjacency
operators $A_w^\pm$ on the quotient induced from the colored adjacency
operators $A^\pm$ on the building for $PGL_3$ contains the simultaneous
spectrum of $A^\pm$ and another hypocycloid with three cusps. As a byproduct,
we re-establish a proof of the fact that $PGL(3,\mathbb{F}_q[t])\backslash
PGL(3,\mathbb{F}_q(\!(t^{-1})\!))/PGL(3,\mathbb{F}_q[\![t^{-1}]\!])$ is not a
Ramanujan complex, from a combinatorial aspect.
