AC Smells Like Mold

I live in Tucson, Arizona. Last year around this time my heater core exploded all over the interior passenger seat floor. About about a month after I replaced the heater core the air conditioning started smelling like mold. The smell only lasts for about a minute and a half when I turn on my car and then it goes away until I turn my car on again.

I have been told that this problem is anything from mold growing from the condensation on the A/C to my freon going bad.

I had my system flushed and cleaned which stopped the smell until the summer months came around. Then it started up again. I have had my car in the shop about 7 times for this problem. I have also sprayed disinfectant in all of the intakes several times. Nothing seems to help when its hot.

Any help or advise would be much appreciated.

you live in an arid climate, so unless it was allowed to build up, there should be no reason mold has infested the system; however, you did mention a month plus was allowed to elapse before the repair. puddled glycol could have built up in the ducts, and dried there.

open up the duct housings (in other words, take the vents off) and spray a mixture of bleach/water in there via a regular spray bottle, but with a small rubber hose attached to the nozzle to allow you further into and around the duct passageways.
this may or may not take care of the issue. if it diminishes it, you may have to pull a couple of the ducts from the dash to scrub them out.

hope this helps,
chris
nrt racing