The gas ignites, has a good flame but still only burns for 5 seconds then shuts off, then repeats that cycle. I have completely cleaned any lint and residue from the ductwork and all components of the unit. Run the unit with the front cover on. I have replaced the blower wheel, ignitor, burner assembly and 3 solenoid coils (old style). The flame sensor and hi-limit thermostat have tested for good continuity (could they still be the problem and is there another way to test them?). Are instructions included with the replacement valve? Thank you very much.
Answer Hello Tony,
The only way to check the thermostats is if you are able to monitor and control the temperature where the thermostat is while checking for continuity of same. This is the only way to test the open/shut temperature of the contacts inside the thermostat. This is done at the factory to calibrate the thermostats, (and quality control). The issue can be caused by a high limit thermostat opening prematurely. Most of the time, the issue you are describing is caused by a faulty coil or gas valve. Of course we are not there to conduct the diagnosis, so all we can do is state the obvious. There is also the possibility that neutral can be dropped through the centrifugal switch in the motor. This completes the heating circuit.
I seriously doubt that instructions will come with the gas valve, but it is a simple part replacement. Of course you should dis-connect the power supply and turn the gas off before beginning.