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Rick
Rick, HVAC Supervisor
Category: HVAC
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Experience:  40+ yrs. experience as a licensed oil & gas technician.
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AO Smith gcv 40 100. Pilot light wont stay on. The thermocouple

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AO Smith gcv 40 100. Pilot light wont stay on. The thermocouple has some kind of transistor in the wiring. DO I NEED a thermocouple with this transistor, or will any from a hardware store work?

Rickheatdoc :

Welcome to Just Answer, I will do my best to help you with your problem

Customer:

OK

Rickheatdoc :

I can't say for sure without a model number but on some new water heaters you have to replace the entire pilot assembly not just the thermocouple. Why do you want to change it?

Customer:

Model gcv 40 100

Customer:

The pilot will not stay lit

Customer:

Owner has been lighting it constantly and now the auto light for the pilot wont work either

Rickheatdoc :

The only time the thermo needs to be replaced is if the pilot goes out when the pilot light button on the gas valve is released after the pilot is re-lit. The pilot could be going out because the air intake vents are clogged. If they are there is turbulence whenever the main burner shuts down which can put out the pilot. If the piezo igniter isn't working either then replacing the pilot assembly may be the best option but before you do I would make sure the pilot burner orifice is not clogged. You should pass a tiny wire through it even if you can see daylight through the tiny hole in the orifice

Customer:

Why does the thermocouple have a transister in the line and can I replace it with one from a hardware that does not have the transistor?

Customer:

IF I NEED TO, That is

Rickheatdoc :

No you can

Rickheatdoc :

can't replace it with a generic universal thermocouple.

Rickheatdoc :

sorry I hit enter inadvertantly

Customer:

Ok, would you possibly have the part number for the pilot assembly?

Rickheatdoc :

Give me a minute to look it up. But before you go and replace it I'd try cleaning the pilot orifice. Of course if you replace the assembly then that won't be necessary.

Customer:

This is a natural gas water heater.

Rickheatdoc :

I know, back in a few

Rickheatdoc :

Ok, first the 'transistor' is a thermal cut out device so if it has 'tripped' you'd have to replace the pilot assembly anyway. Be sure the intake vents are clean and the flue is clear just in case. There is no specific part number for the pilot assembly that I can locate. Go to any plumbing supply house that sells AO SMith and ask for the pilot assembly. You'll need the model and serial number.

Customer:

Thanks for your help.

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