Rheem RGPH-07EAMGR Error Code 3 Blinks (2-sec pause): Limit Switch Is Open
What Does Code 3 Blinks (2-sec pause) Mean?
The 3-blink status code on the Rheem RGPH-07EAMGR indicates the high-temperature limit switch has opened. The limit switch is a safety device that shuts off the gas burners when the furnace temperature exceeds safe operating limits. The blower will continue running to cool the heat exchanger.
The limit switch trips when there is insufficient airflow across the heat exchanger, causing heat to build up inside the furnace. When the temperature inside the furnace reaches the limit switch's setpoint, it opens the circuit and shuts off the burners.
The most common cause by far is a dirty or clogged air filter. A restricted filter prevents enough air from flowing over the heat exchanger, causing the furnace to overheat. Blocked or closed supply and return registers throughout your home can have the same effect. Less commonly, a defective blower motor that is not moving enough air, a defective limit switch, or a loose wiring connection at the limit switch can cause this code.
Common Causes
How to Fix It: Replace the Air Filter and Restore Airflow
What You'll Need
- Replacement air filter (correct size for your system) 🛒 Find at FiltersFast · 🛒 Find at Amazon
- Flashlight
Steps
- Turn off electrical power at the breaker and shut off the gas supply valve Locate the furnace circuit breaker and flip it to OFF. Turn the gas shutoff valve to the OFF position (perpendicular to the pipe). If you smell gas, leave immediately and call your gas company.
- Check and replace the air filter Remove the air filter from the return air duct or furnace filter slot. If it is visibly dirty, clogged, or has not been changed in over 3 months, replace it with a new filter of the correct size. Make sure the airflow direction arrow on the new filter points toward the furnace.
- Verify all supply and return vents are open Walk through every room and ensure all supply registers and return grilles are fully open and not blocked by furniture, curtains, or rugs. Even a few closed vents can significantly restrict airflow and cause overheating.
- Inspect the blower area With the power off, look at the blower wheel through the access panel opening. Check for excessive dust buildup on the blower blades, which can reduce airflow.
- Restore power and gas, then test Turn the gas supply valve to ON and flip the circuit breaker to ON. Set your thermostat to call for heat and monitor the furnace through a full heating cycle.
When to Call a Professional
Contact a licensed HVAC technician if:
- Code 3 returns after replacing the filter and opening all vents
- The blower motor does not seem to be running or makes unusual noises
- The furnace overheats repeatedly even with a clean filter
- You suspect the limit switch itself is faulty
✓ Verified against manufacturer service manual — March 2026