Moved in new Florida home 3.5yrs ago. Occasionally A/C stops cooling although the unit is running and thermostat is on. Called A/C service about 2 yrs ago who suggested turn off unit in case of frozen pipes and using the shop vac to clear water in the pipes. But this time there is no water buildup and no frost and although unit is running, the house is not cooling off. What else could be the issue? Why does the issue repeat every few months. We lived in our previous (new) home for about 2 yrs and not once we had to service the unit, use a shop vac, or worry about flooded pipes. Could we have received a bad unit? Any ideas / suggestions?

You need to call for service. If the unit is only 3.5 years old and the coils are not frozen and there is no water in the pipes, then it is possibly some capacitor stuck in the open or on position that needs replaced. And no, you didn't get a bad unit. If you live in Florida where it gets extremely humid at night this could also help wear out your unit. I lived in South Florida and my unit would freeze up when it was extremely humid out at night. If the coils were not frosted over it invariably was a component frozen in the open or on position. Easy fix once it's properly tested with a voltmeter.

Thanks for the advice. I called for service and now have some follow-up questions.

It turns out the fan motor went bad and, because we ran the unit w/out the fan, the hard start also had to be replaced. Total $680 ($430 for the fan motor and $250 for the hard start). Thankfully the condenser is OK.

But the unit was very dusty (typical for a Lennox due to bad filter intake installation) so I had another tech come in to do a detailed cleaning. This 2nd person reported that we have mold underneath the coils. It has not spread to any other part within the unit, but to be cleaned the coils must be removed to avoid spreading the mold. This makes sense to me, but I don't really know how bad it is or if it is normal to have 'some' mold in Florida. The estimate is around $625 to take apart and do some special mold cleaning & prevention - Then another $925 to install an Air Purification System that will kill any further mold that is sucked in. We are talking about another $1600.

Questions are -- Is this standard practice or am I being offered a non-essential and expensive fix to an easy to solve problem? Can I get a better deal for cleaning the mold of the coils? Is it true that I 'should' install the Air Purification System to avoid remaining mold in the air going into other parts of the unit? Thanks in advance!!