My technician, Richie S., was everything you could want in seeking help with HVAC problems.
I was alarmed by a clanking noise when a multi-task contractor (recommended on the Home Depot pro referral site) changed a filter in such a way that indicated he didn't understand much about the task. Richie came and quickly found the source of the problem and checked over the cleaning of the unit where he corrected another problem. Even though this other person said he built houses from the ground up I will alway go with a certified specialist and Mar Go which is the worry-free choice to do the job right the first time.