How To Install A Vapor Sensor On A Gas Water Heater Showing A Lockout Error Code

9 May 2016
 Categories: , Blog


The vapor sensor on a gas water heater is a safety device that switches off the burner assembly if a gas leak is detected. Malfunctions and water damage can cause a vapor sensor to stay in the locked position even if there isn't a gas leak, which means you will have no hot water until the part is replaced. Most modern water heaters have digital diagnostics and this problem will likely read as a flammable vapor sensor lockout.

Switching out the vapor sensor isn't difficult from a labor standpoint. But you need to be absolutely certain the sensor is locked due to a malfunction, rather than an actual gas leak, and the new sensor needs to be installed correctly or you could risk a dangerous leak or explosion. If you have any doubts at all, call in a plumbing services company to replace the sensor.

Things You Need:

  • Pliers
  • New vapor sensor with bracket

Step 1: Remove the Old Vapor Sensor

Turn off the gas supply at the shut-off valve on the line attached to the water heater. Unplug the water heater from the electrical socket.

Locate the access panel on the bottom of the water heater. Pull up and out on the panel to remove and place the panel aside somewhere safe. Locate the vapor sensor, which is mounted on a bracket that slides down over the water heater wall and sets between the wall and the burner assembly cover. Lift up on the bracket to remove the vapor sensor and the bracket.

Use a pair of pliers to disconnect the wires attached to the terminals in the vapor sensor. Discard the old vapor sensor.

Step 2: Install the New Vapor Sensor

Attach the wires to the appropriate terminals in the new vapor sensor, which should also come with a new bracket already attached.

Slide the new bracket over the water heater wall where the old sensor was located.  Put the access cover back in place by pressing the cover inwards and down.

Plug the water heater back into the electricity and turn on the gas supply at the supply valve. Check the digital diagnostics to see if the vapor sensor error message disappears. If the error remains, turn off the gas supply and call a plumber to diagnose the problem. You don't want to risk a gas leak if there's a different problem occurring or if the vapor sensor is actually working properly and locking due to a leak.

If you have problems, contact a plumber like ATA's Plumbing for help.