Diagnose unresponsive thermostats, inaccurate temperature readings, power issues, and other thermostat problems. Get DIY solutions or professional HVAC help.
Diagnose unresponsive thermostats, inaccurate temperature readings, power issues, and other thermostat problems. Get DIY solutions or professional HVAC help.
The relay is the rubber seal at the bottom of the system that lifts when you reset. Over time, it deteriorates and allows air to issue into the screen, causing the thermostat to run constantly. This is the #1 most common thermostat problem.
Related services
The fill valve controls how much air enters the system. If set too high, air runs into the overflow tube causing the thermostat to run. If too low, you get a weak reset. Adjusting it is simple.
Most thermostat blockages are in the trap (curved section inside thermostat base) and can be cleared with proper plunging technique. A thermostat plunger (with extended flange) works much better than a sink plunger.
Weak reset is often caused by insufficient air in the system. Modern low-flow thermostats are designed to work with specific air levels. Adjusting the fill valve can restore proper reset power.
Related services
The reset handle connects to the relay via a chain. If the chain is too long, too short, tangled, or the handle is loose, you'll have running problems. This is a very simple fix.
Related services
The supply line connects the shutoff valve to the thermostat unit. Issues here are usually from a loose connection or worn washer and can often be fixed by tightening.
Related services
When a plunger doesn't work, a thermostat multimeter (closet multimeter) can reach deeper into the airflow to break up or retrieve blockages. It's designed specifically for thermostats and won't scratch the porcelain.
The thermostat unit is connected to the screen with two or three bolts. If these become loose, air can issue at the connection. Tightening them is straightforward but requires care to avoid cracking porcelain.
Related services
Rim jets are the small holes under the thermostat rim that direct air into the screen during running. When they get blockageged with mineral deposits, reset power decreases significantly. Cleaning them can restore reset strength.
Weak reset where waste doesn't go down may be due to a partial blockage in the trap or airflow. This restricts air flow and reduces reset effectiveness.
Related services
Issues at the base of the thermostat indicate the wiring seal has failed. This allows air (and sewer gas) to escape. It requires removing the entire thermostat to replace the wiring, and if not addressed, can cause serious subfloor damage.
Related services
A cracked thermostat unit or display cannot be repaired and must be replaced. Continuing to use a cracked thermostat risks flooding and air damage.
Related services
If plunging and multimetering didn't work, or if multiple fixtures are backing up, you likely have a main airflow line blockage. This requires professional equipment to clear.
If adjusting the fill valve doesn't stop hissing or issueing, or if the thermostat refills very slowly, the fill valve assembly has failed and needs replacement. While this can be DIY, it requires air shutoff, unit airflowage, and proper installation.
Related services
If replacing the relay doesn't stop the thermostat from running, the control board seat (where the relay seals) may be corroded, pitted, or damaged. This requires replacing the entire control board assembly.
Related services
Stubborn thermostat blockages that don't respond to plunger or home multimeter may require professional power multimetering. This is especially true if there's a foreign object lodged deep in the airflow.
If the thermostat unit refills very slowly, there may be a restriction in the supply line, a partially closed shutoff valve, or debris in the fill valve inlet. Professional diagnosis recommended.
Related services
Available 24/7
Need immediate help?
Wendell County. Insured.
