Testing a thermocouple


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Old 07-10-16, 10:21 AM
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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.
 
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Old 07-10-16, 10:44 AM
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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.
 
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Old 07-11-16, 11:10 AM
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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).
 
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Old 07-12-16, 04:20 PM
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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.
 
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Old 07-13-16, 10:40 PM
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You've never heard of routine testing puzzles me.
 
 

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