AC and Heater Problems: What They Mean and When to Get Them Fixed

Crossroad Garage service team · Ellensburg, WA

Ellensburg summers can be hot and dry, and winters can be bitterly cold and windy. A working air conditioner keeps you comfortable on a July drive across the valley, and a working heater and defroster are a real safety issue on an icy January morning or a winter trip over the pass. When either one stops working right, it is worth finding out why.

Common AC problems

• Air is not cold, or only a little cool. This is often low refrigerant from a leak, but it can also be a compressor, clutch, electrical or blend door problem.
• Cold air comes and goes. This can point to an electrical issue, a cycling problem or a component that is starting to fail.
• Noise when the AC is on. A grinding or rattling sound can come from the compressor or its clutch.
• A musty smell. Moisture and debris in the system and a dirty cabin air filter can cause odors.
• Water on the floor. A clogged evaporator drain can send water inside the cab.

Refrigerant does not get used up. If the system is low, there is a leak somewhere. Simply adding refrigerant without finding the leak usually means the problem comes back. We look for the source and talk through the repair.

Common heating problems

• No heat or weak heat. Low coolant, a stuck-open thermostat, a clogged heater core, air in the cooling system or a blend door problem are common causes.
• Heat on one side only. On vehicles with dual-zone climate control, this often points to a blend door or actuator.
• A sweet smell or foggy windows. These can be signs of a heater core leak and should be checked promptly.
• The engine temperature gauge stays low. A thermostat stuck open keeps the engine from warming up, which means less heat and can affect fuel economy.

The defroster is a safety system

The defroster uses the AC system to dry the air and the heater to warm it. If your windshield fogs up and will not clear, or the defrost air is weak, you cannot see well in winter weather. A clogged cabin air filter, a blower motor problem or an AC fault can all affect defrost performance.

The blower motor and cabin air filter

If you can hear the system working but little air comes out of the vents, the cabin air filter may be clogged. Dust from gravel roads and farm country, plus wildfire smoke in some summers, can fill these filters quickly. If the fan only works on certain speeds or not at all, the blower motor, resistor or control module may be at fault.

What we check

• Vent temperatures and system performance.
• Refrigerant system pressures and leak checks.
• Compressor, clutch and drive belt.
• Cooling system condition, coolant level, hoses and thermostat.
• Blower motor, resistor and controls.
• Blend doors and actuators.
• Cabin air filter and evaporator drain.

Tips

• Run the AC for a few minutes regularly, even in winter, to keep seals lubricated. Most vehicles run the AC automatically in defrost mode.
• Replace the cabin air filter on schedule, or sooner if you drive dusty roads.
• Keep coolant at the correct level and have its condition checked before winter.

When to come in

Come in promptly if the defroster cannot keep the windshield clear, you smell coolant inside the vehicle or the engine temperature rises. Schedule a visit for weak AC before the summer heat, or weak heat before winter sets in.

See all of our auto and diesel services, or browse more tech tips on the Crossroad Garage blog.