If it has been cleaned and serviced annually, the Oxygen Depletion Sensor (ODS) is probably clogged with dust, dirt and/or pet hair. In which case, the ODS is reading the oxygen level in the room as unsafe for operation.
To clean clean unit will require that you take the front of the heater off. You will find screens on each side of the heater, as well as the top. Depending on which model you have and how old it is, you may find screws under the bottom of th heater.
Once you have accomplished the removal of the front of the heater, using a vacuum with a hose and brush attachment carefully vacuum as much of the interior, as well as the burner that you can safely reach with the brush attachment. Using a canned of compressed air with a straw nozzle (like you clean your computer with), blow out the tip of the pilot tip with a quick blast of air. Then look at the pilot assembly ... about 2/3rds down the pilot from where the flame comes out, you'll see a little hole in the side of the pilot. This is the ODS sensor. Place the straw nozzle just barely into that hole and give it a quick blast of air. More than likely, you'll see debris blow out the other side.
If you see any other dust or lint the vacuuming couldn't reach, blow that away with the canned compressed air. Then vacuum the unit again. Reassemble the cabinet and try lighting again. Make sure the control knob is sitting directly in the pilot position, by depressing the control knob down. If it doesn't go all the way in, it's not directly in the pilot position. Turn the knob a hair one way and then the other, unitil the knob wil depress completely. Push the ignitor button and if the pilot lights, hold the control knob in for at least 60 seconds, then slowly release the Control Knob. If the pilot lights and holds, wait another minute and turn it to the on position. If everything works like it should, you're back in business. If not try lighting it again. If the pilot fails to hold again, the Thermocouple will need to be replaced. Contact a local gas fireplace store in your area or is you use Propane Gas contact them for the Thermocouple replacement.
Keep in mind that DESA International is out of business, but some parts like the Thermocouple are still available. You''ll need the Model Number of your heater to be sure an get the right part.
Answers & Comments
If it has been cleaned and serviced annually, the Oxygen Depletion Sensor (ODS) is probably clogged with dust, dirt and/or pet hair. In which case, the ODS is reading the oxygen level in the room as unsafe for operation.
To clean clean unit will require that you take the front of the heater off. You will find screens on each side of the heater, as well as the top. Depending on which model you have and how old it is, you may find screws under the bottom of th heater.
Once you have accomplished the removal of the front of the heater, using a vacuum with a hose and brush attachment carefully vacuum as much of the interior, as well as the burner that you can safely reach with the brush attachment. Using a canned of compressed air with a straw nozzle (like you clean your computer with), blow out the tip of the pilot tip with a quick blast of air. Then look at the pilot assembly ... about 2/3rds down the pilot from where the flame comes out, you'll see a little hole in the side of the pilot. This is the ODS sensor. Place the straw nozzle just barely into that hole and give it a quick blast of air. More than likely, you'll see debris blow out the other side.
If you see any other dust or lint the vacuuming couldn't reach, blow that away with the canned compressed air. Then vacuum the unit again. Reassemble the cabinet and try lighting again. Make sure the control knob is sitting directly in the pilot position, by depressing the control knob down. If it doesn't go all the way in, it's not directly in the pilot position. Turn the knob a hair one way and then the other, unitil the knob wil depress completely. Push the ignitor button and if the pilot lights, hold the control knob in for at least 60 seconds, then slowly release the Control Knob. If the pilot lights and holds, wait another minute and turn it to the on position. If everything works like it should, you're back in business. If not try lighting it again. If the pilot fails to hold again, the Thermocouple will need to be replaced. Contact a local gas fireplace store in your area or is you use Propane Gas contact them for the Thermocouple replacement.
Keep in mind that DESA International is out of business, but some parts like the Thermocouple are still available. You''ll need the Model Number of your heater to be sure an get the right part.