Testing a thermocouple
#1
Testing a thermocouple
Hi, what is the procedure for testing a thermocouple,I assume if I remove the cap tube from the valve I will loose the pilot.
#2
Pilot on = good thermocouple.
Disconnecting the thermocouple in a working application and having the pilot light go out is one way to confirm it's good. It will take approx 60-150 seconds for the valve to snap shut.
To check with a meter you need to use the lowest DC volts scale. The thermocouple tip needs to be kept in a flame. You measure from the center button to the metal tubing. You need to measure 20 millivolts minimum.
Disconnecting the thermocouple in a working application and having the pilot light go out is one way to confirm it's good. It will take approx 60-150 seconds for the valve to snap shut.
To check with a meter you need to use the lowest DC volts scale. The thermocouple tip needs to be kept in a flame. You measure from the center button to the metal tubing. You need to measure 20 millivolts minimum.
#3
In the absence of a test adapter replacing the thermocouple is probably your best course. Taking what has been described is termed an OPEN read. This can be very misleading. Your meter may show a read of say 20 millivolts. However when a CLOSED read is taken it may show as low as zero. Also without performing a closed read there is no way to obtain a DROPOUT read, meaning a check of the gas valve power unit (magnet).
#4
Member
Does the pilot stay on? If so, the thermocouple is good - if not, replace it. Replacements are cheap and easy to install. I've never heard of performing routine testing.