Heat and Air Handbook

What's your system doing?

Pick the symptom. See what you can safely check yourself, the point where you stop, and what the technician will look at, from the makers' own manuals. We sell nothing.

What's it doing?

You check Thermostat set to heat, furnace switch and breaker on, gas valve on, filter not clogged

Stop You smell gas, or the code comes back after a reset

Technician Ignitor, flame sensor, pressure switch, gas valve, control board

Furnace not turning on

You check Fan set to Auto, a clean filter, and the code on the control board

Stop The burners won't light, or the code repeats

Technician Ignition, flame sensor, limit switch

Furnace blowing cold air

You check Read the light or display through the sight glass and the label inside the door

Stop A lockout code that returns after one reset

Technician Whatever part the code points to

Furnace error codes by brand

You check Thermostat on cool, breaker and outdoor disconnect on, filter, outdoor unit clear

Stop Ice on the lines or the coil

Technician Refrigerant charge, capacitor, contactor, compressor

AC not cooling

What the makers let owners check, where to stop, and what the technician does. Smell gas? Leave the house first, then call 911 or your gas utility from outside.

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How we check.

Makers' manuals by number and date, the federal efficiency and refrigerant rules as they read today, and federal safety agencies. We sell nothing and refer no one.

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