www.hvactechgroup.com - forums

Hello! I have been in this house 2
Years , after 2nd summer after cooling season and when heating season started I noticed vents throughout house have a musty/basement-ish smell. The vents do not really smell when heat is running, I usually notice when heat is off and has not ran often (starting again more so now that we are in spring and it's warming up) I had service in winter and tech did not notice it really (heat had been and was running) he checked drain line and filter both good , since then I have changed filter monthly and I pour a little soapy water down drain line every so often. It's a 15 year old
Trane system - I have no other issues with system. Also I do not know if issue persists during cooling season as issue just started last fall. What could be the issue ? Thank you in advance

It's a Trane XL90

Is there a humidifier installed on the system?  There could be an old filter pad that is causing the smell.

Otherwise check the cooling coil pan is clean.

Thanks for reply
No humidifier.

The coil and pan looks like this
https://ibb.co/bgv3CXM
https://ibb.co/D1V8G42
https://ibb.co/SV59v2V
https://ibb.co/vcTK47Y

Thanks again