Why is mold present on the outside of the furnace/air handler?

Question

I am purchasing my first home, was built 1995. I am 5 days into my due diligence period and today during the walk through I notice mold/mildew on the outside of the furnace/air handler located in the garage. The house was winterized and has been empty since 10/2008. Owners were transferred and relocation company is the seller ( they have only an inspection report to go by so my questions can not be answered) ( inspection was done in oct 2008)

Answer 1

I assume you mean 2007 but the reason there was mold on outside of the air handler is because the condensation allowed the mildew to grow, this can take place for weeks after it is shut-off

Answer 2

If you can see mold on a walk by, the ductwork probably has some in it as well.Check it out.Not an easy fix either short of replacing the effected ductwork.

Answer 3

Is there condensation on the outside of the AH/furnace?  Where is it located in your home (the attic, crawl space, basement)?  Was there mold present in the winter when you were using the heat?

It could be caused by condensation collecting on it because it gets much colder than the surrounding air.

Answer 4

IF the mold/mildew (mm) came from winter time its most likely because the house was not occupied and the temp was let go well down below 50'F. Also be advised that the furnace may have some internal insulation missing or needed. The case of the furnace is usually colser to the indoor temp and wont support mm. If its come from AC use the condisate will be on the outside and will be a problem in the summer months unless you insulate the furnace box to stop the transfer of cool air to the outside warm air in the closet.

You could have water splashing on to the inside of the coil and dripping down causing it to sweat also.

Feel around for cool spots since we are in the cooling mode (assuming Northen Hemisphere).  

The insulation slowes the heat transfer down and usually cuts off the air to metal to air contact allowing the furnace to opperate and the furnace box to not get "as cold or warm" and thus stop the condisate anjd this stops the mm.

Any HVAC guy should be able to do this for you and should not cost over $150.00.

Of cource there may be other needs he may be able to tell you about and if it costs more than I say its just because Im not in your neighborhood and not looking at the problem, so keep thjis in mind if hes qoute is higher (or maybe lower) than my idea.