Thanks Andy for the information you gave me. I'll try your sugestions. The last thing I did was to replace the intake air diaphragm. I did that on 3/8/03. the ignition sequense started and shut down about 20 seconds later, but withing 5-10 seconds it re-started. it has been running good since then until 3/12/03. The ignition sequence started 20 seconds later it stop and the green led on the ignition control module went out, but the blower fan came on. aprx. 10-15 seconds later the led came back on. The furnace is running normally again. Does this tell you anything? Waiting for your reply. Thanks again.