A fault code is the most useful thing a Rheem tells you and the most commonly misread — partly because Rheem uses two different reporting systems depending on the equipment generation. This page is the Rheem-specific companion to our general furnace repair service and our Rheem brand overview, and it splits the two contexts so you are not misled.
Two systems, two places to read the code
Be clear which one you have before you read anything:
- Communicating Rheem / Ruud (EcoNet equipment): the fault appears at the EcoNet Control Center — under the Service window in Current Faults, and in the Fault History, each entry time-and-date stamped — using an alphanumeric alert format. The same fault also flashes on the indoor control board’s LED.
- Conventional Rheem / Ruud (older furnaces and air handlers): a diagnostic LED on the control board flashes the code, read through the inspection port on the lower panel. Some boards use a single LED with short/long bursts; others use two LEDs, one per digit.
The two systems do not share a numbering scheme, so a control-board flash count and an EcoNet alert are read in different places and mean different things. Below, each section is labeled by context.
Conventional control-board LED codes
Older Rheem and Ruud furnaces flash a diagnostic LED — typically a slow blink during a normal call for heat and a repeating pattern for a fault that you count.
Important honesty note: Rheem used several different control boards across furnace models and generations, and the exact number-to-fault map is not uniform between them — a given flash count can mean different things on different boards, and single-LED and dual-LED models read differently. Multiple service references say the same thing: consult the legend on the furnace door or in the unit’s manual for your specific board. Rather than publish a generic flash chart that may not match your board, we describe the subsystems the board flags — and confirm the actual fault on the meter:
- Pressure / venting — the pressure switch did not close (often a weak inducer, a clogged condensate trap, or a blocked vent), or closed when it should be open.
- Limit / overheat — the high-limit opened from restricted airflow: a clogged filter, blocked registers, or a dirty blower. The same airflow chain is in our furnace short-cycling guide.
- Ignition — failed ignition attempts, which after a set count put the furnace into a one-hour lockout (see below).
- Flame sense — the furnace lit but could not prove a stable flame, covered on our Rheem furnace not heating page.
The one-hour lockout
One behavior is consistent across Rheem controls and worth calling out: after a set number of failed ignition attempts or a persistent safety trip, the control enters a one-hour lockout — it stops trying and will not fire for about an hour to prevent gas buildup and protect the equipment. On a communicating system this surfaces as an EcoNet alert; on a conventional board it shows in the flash pattern. It is a safety response, not a glitch, and cutting power to clear it just restarts the same failed sequence. The underlying cause is usually a worn ignitor, a fouled flame sensor, a gas-supply issue, or a pressure/venting fault — which is what we diagnose.
EcoNet alert codes
On a communicating system, EcoNet displays an alphanumeric alert (for example A010_F) and logs it with a timestamp. The codes we can document with confidence:
| EcoNet alert | Meaning | Confidence |
|---|---|---|
| A010-type | One-hour lockout — system locked out to protect against rapid cycling or a repeated fault | High |
| A100-type | Configuration-data restore failure — usually indicates corrupt air-handler control-board firmware (board attention) | High |
| A905-type | Usually indicates an inverter DC-bus under-voltage fault — compressor stops while the air handler runs | Medium |
| A111-type | Usually indicates an EXV/EEV temperature-thermistor fault (the suction sensor that drives the expansion valve) | Medium |
| Coil-temp sensor | Usually indicates a condenser coil-temperature sensor reading out of range — sensor replacement | Medium |
A note on accuracy: Rheem publishes EcoNet alert charts that are specific to each equipment family (air handler, 2-stage AC, inverter), and the alert suffix varies by unit, so we read your system’s exact code against the current Rheem chart for that model. The medium-confidence entries above are phrased cautiously on purpose — we confirm the failed part on the meter before quoting, never from the alert alone.
Reading the code is the start, not the fix
Here is the honest part. A code — LED or EcoNet alert — names a subsystem, not a failed part. A pressure fault can be a $0 clogged-trap clean or a $580–$1,100 inducer; a limit fault can be a filter you change yourself or a heat-exchanger problem you should not ignore; a flame-sense fault can be a $185–$295 sensor clean or a gas-pressure problem. We read the code on arrival, then confirm it on the meter — flame-sense microamps, draft pressure at the inducer, limit continuity, refrigerant pressures, bus voltage — and only then name the part. We do not guess from the code alone, and we do not jumper a safety to force a system to run. The flat $89 diagnostic ($149 after-hours) credits to the repair, so the read-and-confirm step costs you nothing if you proceed.
The SoCal pattern behind the codes
Most of these surface on a schedule. The heating codes (ignition, flame-sense, pressure, limit) cluster on the first cold night in November, when an idle furnace fires hard for the first time in eight months and a dust-coated flame sensor or a tired ignitor finally gives out. The cooling-side EcoNet alerts cluster in the first inland heat waves — a coil that is fine at 80°F cannot reject heat at 104°F in Pasadena or Riverside. On the coast in Santa Monica, Manhattan Beach, and Malibu, salt-air corrosion drives sensor and electrical faults earlier in the unit’s life. Fall and spring maintenance catch most of these before they become a no-heat or no-cool call.
Rheem diagnostic pricing
Reading and confirming the code is the $89 diagnostic ($149 after-hours), credited to the repair. The repair price follows the cause, flat-rate from our SoCal tickets: flame sensor $185–$295, hot-surface ignitor $245–$485, gas valve $385–$685, integrated control board $480–$950, draft inducer $580–$1,100. A cracked heat exchanger ($1,500–$3,500) is the one fault where we quote replacement against repair and red-tag the furnace if it is leaking. Full furnace table on our Rheem furnace repair page; refrigerant-circuit faults are priced with the cooling side on Rheem AC not cooling.
EcoNet and older Rheem systems
We diagnose both the current EcoNet-communicating systems and older conventional Rheem and Ruud units that report on the control-board LED. For the cooling side of a Rheem system, see Rheem AC repair, and the full lineup on our Rheem brand page.