Air conditioners almost always warn you before they quit. The warnings are just easy to explain away in July, when the house is mostly comfortable and nobody wants to think about a repair bill.
Below are the signs worth paying attention to, what usually causes each one, and how urgent it is. Three of them mean shut the system off and call somebody, and we have marked those clearly.
1. It runs constantly but the house never quite gets there
A system that runs all afternoon and holds at 78 when it is set to 72 has lost capacity. The usual causes are a low refrigerant charge from a leak, a dirty condenser coil rejecting heat poorly, a dirty evaporator coil, or a failing compressor that is no longer pumping to specification.
It can also mean the system is simply undersized for a house that has been added onto, or that duct in an unconditioned attic is losing cooling before it reaches the room.
Urgency: get it looked at. Running a system that cannot keep up wastes electricity and puts hours on a compressor that may already be struggling.
2. Warm air from the vents while the outdoor unit is running
If the blower is moving air and the outdoor unit is spinning, but the supply air is not cold, the two most common causes are a refrigerant charge low enough to stop meaningful heat transfer, or a compressor that is running electrically but not compressing.
Urgency: same day if it is hot out. There is nothing to be gained by letting it run in that condition.
3. Ice on the refrigerant line or the indoor coil
Ice looks like the system is working hard. It is the opposite. Ice forms when the coil temperature drops below freezing, which happens when airflow is restricted or the charge is low. A frozen coil starves the compressor of returning vapor and sends liquid refrigerant back to it, which is one of the fastest ways to destroy one.
Shut it off. Turn the cooling off at the thermostat, leave the fan on to help the coil thaw, replace the filter if it is dirty, and call. Do not chip at the ice.
4. The breaker trips, and someone keeps resetting it
A breaker is a safety device reporting that the circuit is drawing more current than it should. On an air conditioner that usually points to a failing compressor, a seized fan motor, a weak capacitor, or a wiring fault.
Shut it off. Reset a breaker once. If it trips again, leave it off. Repeated resets on a hard electrical fault are a fire risk, and they will not fix anything.
5. A burning, hot plastic or fishy smell
Overheating insulation and electrical components smell distinctive, and the fishy or hot plastic version usually means overheated wiring or a component running hot enough to damage itself.
Shut it off at the thermostat and at the disconnect, and call. This is not a wait-until-Monday item.
A musty or sour smell is a different problem. That is usually biological growth on a wet evaporator coil or a stagnant condensate trap, which is unpleasant but not dangerous.
6. New noises, and what they usually mean
- Screeching or squealing on startup: often a failing blower or condenser fan motor bearing.
- Grinding: a motor bearing that has already gone.
- Loud humming with no start: classic weak or failed run capacitor. The motor is trying and cannot get going.
- Rattling from the outdoor unit: loose panel, debris in the fan cage, or a compressor moving on failed mounting grommets.
- Hissing: a refrigerant leak, or a duct leak on the pressurized side.
- Clicking that repeats: a relay or contactor trying and failing to pull in.
Urgency: a humming no-start is often an inexpensive capacitor. Grinding means shut it off before the motor seizes and takes something with it.
7. Short cycling
Starting and stopping every few minutes is hard on a compressor, because the startup draw is where most of the electrical stress lives. Causes include an oversized system, a dirty condenser coil driving head pressure up until a safety opens, a low charge tripping a low pressure switch, a failing thermostat, or a restricted filter.
Urgency: soon. Short cycling shortens equipment life measurably and it usually points at something specific and fixable.
8. Water where water should not be
Standing water around the indoor unit, a wet ceiling below an attic air handler, or an overflowing drain pan means the condensate line is clogged or the trap is dry. It is a small repair that turns into a large one if it sits.
Urgency: prompt, especially with an attic or upstairs unit. If water is near electrical components, shut the system off.
Age is context, not a diagnosis
A well maintained system commonly runs fifteen to twenty years in Colorado. Our dry climate is easier on equipment than a humid coastal environment, and hail is the local variable that shortens condenser life.
Age matters most when it changes the repair math. On a system over twelve years old, a major repair like a compressor or a large leak on an obsolete refrigerant is a genuine decision point rather than an automatic yes. On a system under eight years old, most single component failures are worth repairing without much debate.
Common questions
Should I add refrigerant if my AC is not cooling?
A sealed system does not use refrigerant. If it is low, there is a leak. Adding refrigerant without locating and repairing the leak means paying for the same refrigerant every year and venting it in between.
My AC froze up. Can I just turn it back on after it thaws?
You can, but if you have not fixed what caused it, it will freeze again and each cycle is hard on the compressor. Freezing has two root causes, restricted airflow and low charge, and both need to be checked.
How much does an AC repair typically cost?
Capacitors and contactors are the least expensive common repairs. Motors and control boards sit in the middle. Compressors and evaporator coils are the repairs that trigger a replacement conversation. Any company should be able to give you a firm number after diagnosis, before work starts.
Is it worth repairing an air conditioner that uses R-22?
Sometimes. R-22 has not been produced or imported since 2020, so the cost of a significant recharge is high and rising. A small electrical repair on an R-22 system can still make sense. A large refrigerant leak usually does not.
If something on this list sounds familiar
GoodFellas runs air conditioning service across Northglenn, Thornton, Westminster, Broomfield, Arvada, Longmont, Boulder, Brighton, Erie, Lafayette, Louisville, Superior, Wheat Ridge and Commerce City. Our technicians diagnose first and quote before they start work.
Call (303) 457-4328 or request service.
