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Coleman DGAT075BDE intermittant short cycle

Posted: Sat Dec 31, 2016 12:57 am
by ds165dgat
The short cycle happens randomly, furnace short cycles one or two times and satisfies thermostat. There are no code errors. The short cycle occurs randomly couple times a week, during my daytime observations. Tonight the furnace short cycled three times and gave an ignition failure code. Reset the furnace with the on/off power switch and the furnace appears to be running a normal heat cycle for the moment. The flame sensor has been gently cleaned about a month ago and I've measure the sensor amps, which range from 1 to 3.5 micro amps for a normal cycle, with average of 2.5 micro amps as indicated on digital meter. The only conclusion I have come to is that the flame sensor getting weak, or control board components getting weak, and or random variation In gas pressure????? The furnace is 20 years old and the flame sensor and control board are original. Do you have any suggestions and what else could I check for.
thanks ds165dgat