But lots of people are going to be more likely to pay for unnecessary repairs and replacement than usual because they can't bear the thought of losing their comfort.
I've taken care of 40 plus older residential units for ten years and in that time exactly TWO AC systems have had to be replaced. Both were WELL over 20 years old.
It pays for you to know what your outside unit - the condenser - sounds like when it's running well.
Before a compressor fails it will start to make more noise/ get louder than usual, this may continue for days, weeks or even years. But do make a note of it. Chances of that compressor suddenly failing without warning -getting louder-a re very low.
There are two common failure parts in the condenser:
The power relay called a 'contactor' and the motor capacitor{s}. When the AC suddenly quits working, odds are over 90% it's one or the other at fault.
If the capacitor fails, the fan and/or the compressor tries to run but cant get started.
- Retail price of capacitor: $25-$35
If the condensor fan motor itself fails, it will be relatively hard to turn. It should react like a pedestal fan. Easy to turn.
With thermostat in 'Off' position, try to turn the fan with a ruler or thin wood piece. If it's stiff or hard to turn, the bearings are bad.. actually usually 'dry' but it may not be worth having it lubricated. It has sealed bearing and must be disassembled to do it.
- Chances of fan motor failing electrically - almost zero. If it turns easily, and tries to start but wont.. chances of bad capacitor about 99%.
Retail price of fan motor: $150-$200.
If the outside unit does nothing at all, listen for a faint hum. That is the relay coil trying to start it. It is getting a signal from your thermostat. The A/C breaker may be tripped, in your inside box, the fuse {if any} in the outside box may be blown or the relay may be bad.
- If there's no hum, check to see if you can turn the furnace blower on by changing thermostat switch from 'auto' to 'on', your furnace breaker may be tripped or there's an electrical problem in your furnace controls.
- If there is a hum, the compressor and fan do nothing, and your outside unit is getting power, that relay/contactor is probably bad. Common in ten year old or more.
Ice on lines to condenser unit. Means bad furnace airflow 90% or low refrigerant - not likely because it only happens at a certain point of capacity. Change filter or your furnace blower is bad or blocked air return registers.
If the outside lines have ice, that means your inside coil is a solid block of ice. Turn heat/cool OFF, furnace blower 'ON' and allow at least 2-3 hours for ice to melt. You will likely have water puddling around the furnace when that's done.
Use cheap furnace filters in cooling season. The wet inside coil gets those little bits of dust anyway. and the airflow is better.
more later as I think of it.
