I AM WORKING ON A COZY W501E WALL FURNACE AND CANT GET THE PILOT TO STAY LIT. i HAVE CHANGED THE GAS VALVE, THERMOCOUPLE,AND THE SENSOR FOR THE HIGH LIMIT. THE PILOT WONT STAY LIT
Pretty much the only thing that will do that is the thermocouple not generating enough voltage for the valve to say it's OK. Usually you need to hold the button for pilot lighting for 60 seconds. You can use a meter to check that it's generating enough power. The thermocouple has to be in the pilot flame properly.
Check this video: https://www.youtube.com/watch?v=suen7QlJl4o
Gas furnace will not light Thermocouple test with the multimeter
Or see this site: How to Test Thermocouple with Multi Meter Heating and Cooling
Answers & Comments
Pretty much the only thing that will do that is the thermocouple not generating enough voltage for the valve to say it's OK.
Usually you need to hold the button for pilot lighting for 60 seconds. You can use a meter to check that it's generating enough power. The thermocouple has to be in the pilot flame properly.
Check this video:
https://www.youtube.com/watch?v=suen7QlJl4o
Gas furnace will not light Thermocouple test with the multimeter
Or see this site:
How to Test Thermocouple with Multi Meter Heating and Cooling