Rheem Furnace Clicking But Not Starting: Causes & Fixes

Last updated Oct 3, 2026 · By fixme.vip Editorial

Rheem furnace clicking but not starting: what it means

“Clicking but not starting” isn’t a numbered fault code — it’s a symptom. On a Rheem gas furnace you hear a repeated click (often from the integrated furnace control board relay or the gas valve) but the burners never light and the furnace won’t run a full heat cycle.

The click is usually the control board energizing a relay or the gas valve as it tries to begin the ignition sequence. When ignition or flame proving fails, the board stops, pauses, and tries again — producing that characteristic repeated clicking. After a set number of failed attempts, the board goes into a lockout and flashes a diagnostic code on its status LED.

On most Rheem upflow furnaces, the control board sits in the blower compartment, so you view the LED through the small window in the lower (blower) door, not the burner compartment. Leave the door in place while you look: removing it opens the door-interlock switch, cuts power to the board, and clears the code you’re trying to read. Rheem and Ruud integrated furnace controls typically report faults as a count of flashes, but what each count means varies by board, so match what you see to the code chart for your specific control.

Because the gas valve and ignition system are involved, this is a pro-level repair once the simple homeowner checks are done.

Rheem furnace clicking but not starting: common causes, ranked by probability

This ranking assumes the burners never light at all. If the burners light and then shut off within a few seconds, a flame sensor problem is at least as likely as igniter failure and is often the first thing to suspect.

1. Failing or dirty hot-surface igniter — the board calls for heat and clicks, but a cracked or worn igniter won’t reach ignition temperature, so burners never light.
2. Control board relay fault — a worn relay on the integrated furnace control (IFC) clicks but doesn’t reliably pass power to the igniter or inducer.
3. Failed draft inducer motor or inducer relay — the inducer relay clicks, but the inducer motor doesn’t start or doesn’t come up to speed. The pressure switch never closes, so the board won’t continue to ignition.
4. Flame sensor fault — burners may light briefly, then the board shuts the valve and re-clicks because it can’t prove flame (overlaps with Flame Sensor Problems).
5. Open or intermittent safety switch — a tripped limit switch, rollout switch, or pressure switch stops the sequence; the board clicks trying to restart.
6. Weak low-voltage transformer — a failing 24V transformer can’t hold relays or the gas valve open, causing repeated clicking and dropout.
7. Gas valve not opening — the valve solenoid clicks (energizes) but fails to open, so no gas reaches the burners.
8. Loose or corroded low-voltage wiring / connectors — intermittent connections cause the board to cycle and click.

After repeated failed attempts, Rheem IFC boards go into lockout, but lockout behavior and duration vary by control board. Many boards use a timed soft lockout that automatically retries after about an hour. A furnace that keeps locking out has a fault that a technician needs to find; resetting it won’t fix the cause. Watch the flashing fault light to pin down the specific fault — see Rheem Furnace Flashing Light and Rheem Furnace Ignition Lockout for code meanings.

How to fix Rheem furnace clicking but not starting: safe checks first

These are the only steps a homeowner should do:

• Gas smell: If you smell gas at any point during the clicking, do not reset the furnace or touch any switches. Leave the home and call your gas utility or 911 from outside.
• Thermostat: Confirm it’s set to Heat and the setpoint is above room temperature. Replace the batteries if it’s battery-powered.
• Air filter: A badly clogged filter can trip the limit switch and interrupt the cycle. Replace a dirty filter with one that matches your existing filter’s size.
• Breaker / furnace switch: Check the furnace breaker and the service switch (looks like a light switch near the unit). Reset the breaker once if tripped.
• One reset: If the furnace is locked out, cycle power at the breaker or switch one time only. Do not repeatedly reset a locked-out unit.
• Vents and registers: Make sure supply and return vents are open and unblocked, which helps prevent limit-switch trips.
• Condensate line (high-efficiency models): If you have a condensate drain, check that it isn’t clogged or backed up, which can trip the pressure switch.
• Panels: Confirm the burner/blower door is fully seated — a loose door opens the door-interlock switch and prevents startup.

If the clicking continues after these checks, stop and call a licensed HVAC technician.

How a technician will diagnose it

A technician will:

• Read the flashing fault code through the blower-door window and note the ignition sequence.
• Measure 24V output from the transformer and check for voltage drop under load.
• Test the hot-surface igniter for continuity/resistance and confirm it glows.
• Check the flame sensor microamp signal and clean or replace it as needed.
• Verify the inducer motor starts and runs, check the inducer relay output on the board, and confirm the pressure switch closes.
• Test the limit and rollout safety switches for continuity.
• Confirm the gas valve opens and gas pressure is correct with a manometer.
• Inspect the control board relays and low-voltage wiring for corrosion or loose connectors; replace the board if a relay has failed.

This sequence lets you sanity-check a quote — a good tech confirms the actual failed component rather than replacing the board blindly.

Symptom, cause and what to do

Rheem furnace clicking but not starting repair cost

Honest US ranges, parts and labor included:

• Air filter (DIY): $10–$40
• Thermostat batteries (DIY): $5–$15
• Hot-surface igniter: $150–$350
• Flame sensor cleaning/replacement: $90–$250
• Pressure switch: $150–$350
• Limit or rollout switch: $150–$400
• Low-voltage transformer: $150–$300
• Draft inducer motor (or inducer relay/board repair): $400–$1,200
• Integrated furnace control board: $400–$1,200, higher for variable-speed or high-efficiency boards
• Gas valve: $400–$1,000+
• Diagnostic / service call: $80–$180 (often credited toward the repair)

Prices vary by region and model. Older, variable-speed, or high-efficiency components generally cost more.

Related codes

Rheem Furnace Won’t Ignite, Rheem Furnace Ignition Lockout, Rheem Furnace Flame Sensor Problems, Rheem Furnace Keeps Shutting Off, Rheem Furnace Short Cycling, Rheem Furnace Won’t Turn On, Rheem Furnace Blower Not Running, Rheem Furnace Flashing Light.