Performed diagnostic on commercial units Roseville. Rooftop gas package units. 3 carrier units. Filters 12-20-1 x 4 2 per unit. Units haven’t been serviced in 2 yrs 2017 last time filters where changed. Units aren’t in that good of shape, had some weird wiring issues on unit 2 which is middle unit on roof, tstat front right room. preventing the unit from running. My recommendation is to sign back up on the maintenance plan and slowly start tackling the issues of neglect.