We purchased a house in 2010. The A/C was working fine, but during day time in hot summer, the upstairs unit can't keep the upstairs below 80 while the downstairs unit can keep the downstairs at 78 degree without any issue. The upstairs was too hot (80 degree) even though it can keep the house at 78 at night time or when there is no sun light outside. So we called in a A/C technician and he checked out everything and he said that the attic is too hot. He recommended the install of the attic fan. But I asked around and my neighbor said that the house has good ventilation and enough insulation. Anyway, I did not do any further action due to some family issues.
Today, I brought a A/C tech from the company who installed the A/C originally. First, he said that everything seems to be working fine because the A/C was able to reach 79/80 degree as he changed the thermostat; it was 12:10 p.m. and outside temp was about 91-92. And he went outside and checked the freon level. He said that both of the units are low on freeon. And most likely, the evaporator coils are leaking. I asked him if there is any possibility that something else is wrong. But he does not see any leak and wants to open up the coil, but I asked him not to do it yet. In the past, one guy opened up the coil and created the leak because he sprung the coil. I wanted to be more careful before I allowed him to do anything he wanted. And the guy wanted the extra money to do the leak detection. If he is sure about the problem, I would like to save the money to pay for the coils...
Anyway, after he recharged the Freon, the upstairs unit can keep the house around 77/78. That is good news. the Freon was low for some reason. He quoted me $$$$ for the replacement of the coils. I am glad that this is not ventilation issue, but I may have to do something to address the freon issue.
1. Both of the units are a little over 5 years old. Warranty has expired for both of the units. But how can both of the units have leaks at the same time. If one unit has leak and other other does not have a leak, I would believe it.
2. Last year, the best temperature it was able to keep was 80 degree in hot summer day. This year, it can do the same thing. But at night, the cool air comes from both of the units. If there was a leak, why does the A/C show the same performance this year?
3. Is there a way I can check the leak of the coils without opening up the unit? I know that there is a detector. I can purchase it, but can I put that it on the return vent and have the same result? The coil has a tube coming out. It has a huge gab. If I stick it in the detector into it...can I detect the leak?
4. Is there any possibility that Freon was low from the beginning of this house? A/C seems to be working fine except it could not cool the house during hot days (94 or higher) outside.
I want to give more thoughts on this issue before I commit myself to any big purchases. Any advice or help would be greatly appreciated.