I have a Trane XE 80 A/C, gas heater combination unit. For a few months now, there has been a "musty" smell. My A/C guy checked it out and put a liquid chemical cleaner behind the filter that was then spread through the system via the fan (it was not applied to anything directly). That seemed to take care of it for a while, but now the odor is back. Also, the filter, which I replace regularly (3M), has moisture collecting on it to the point that the metal stabilizers in back sometimes have some rust on them. I mentioned this to my A/C person as well, but he just says neither he nor his boss have any idea what might be causing this accumulation of moisture. He also claims the inside part of the A/C unit is "self-contained" and cannot be cleaned (he serviced the condensator (?) outside and cleaned it). I would just get another A/C person, but I have a maintenance contract with these guys (long story of company resales) and would loathe to pay someone else to come out if there's nothing to be done.
I have searched the hvac forums in vain for any information on this type of problem with the XE 80 or even a comparable Trane unit (everybody else just seems to have issues with the gas heater auto ignition). Any ideas? I also searched for a schematic to see whether the unit is really "self-contained" and "doesn't need cleaning" as the A/C guy stated, but I have had no luck there either (Trane's website doesn't list the XE 80 anymore). The unit is 10 years old and mostly used for A/C. Apart from the odor, I have had no issues with it. The odor clearly seems to originate near the unit and not in the vents.
Thanks for any help in advance! KB