How car A/C works, and why it stops

Your air conditioning moves heat out of the cabin using a refrigerant that circulates in a sealed loop. When it stops blowing cold, the usual causes are a refrigerant leak, a compressor that is not engaging, a cooling fan that has failed or a blend door stuck on heat.

A/C is also what dries the air for your defroster. If the windshield fogs up and will not clear in fall and winter, the A/C system is often the reason.

Signs your A/C needs service

Air from the vents is warm or only slightly cool
Cold on the highway, warm at a stoplight
Weak airflow even on the highest fan speed
Musty smell when the A/C starts
Windows fog up and are slow to clear
Clicking or rattling when the A/C switches on

How we test and repair A/C

01
Performance test
Vent temperature, system pressures, compressor and fan operation.
02
Find the leak
Leak detection so the cause is fixed, not just topped up.
03
Repair
The leaking or failed part is replaced after you approve the quote.
04
Evacuate and recharge
The system is vacuumed down and refilled by weight to the exact amount on the under-hood label.

A/C questions we get asked

Does my A/C need a recharge every few years?

No. Refrigerant is not used up. A system that needs topping up has a leak, and the lasting fix is finding it.

Why is it cold on the highway but warm in traffic?

At speed, air is forced through the condenser at the front of the car. At a stop, an electric fan has to do that job. Warm air at idle often means the fan is not running or the system is low on charge.

What causes the musty smell?

Moisture collects on the evaporator behind the dash, and a clogged cabin air filter makes it worse. A new cabin filter is the first step, and the evaporator can be cleaned if the smell stays.

Can I use a recharge can from the store?

It can get you through a week, but it is easy to overfill the system, which also makes it blow warm. Cans with stop-leak sealer can gum up the system and service equipment.

Which refrigerant does my car use?

Older cars use R-134a. Most newer models use R-1234yf. They are not interchangeable, and the label under the hood says which one your car takes and how much.