Replace Reliance Water Heater Gas Control Valve

No reset button.
The gas control valve is the thermostat
http://waterheatertimer.org/How-to-troubleshoot-gas-water-heater.html#intellivent

Intellivent gas control can be reset, and Honeywell can be reset under some circumstances.
Otherwise, bad thermostat means replace gas control valve

Gene

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1) Replace gas control valve;
http://waterheatertimer.org/How-to-troubleshoot-gas-water-heater.html#intellivent
http://hometips.me/Mar/How-to-replace-water-heater-gas-valve.pdf

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

Used, Reliance 805 is power vent gas
10 year old water heater that is newly installed.
Unknown gas control valve.
I'm not a fan of installing old power vent water heaters.
Usually these things are so expensive that old one is only replaced when it fails.

120Volt Outlet must have correct polarity and unit must be grounded between ground prong on cord to manifold tube connected to bottom of gas control valve. Test for continuity with multimeter.

Is this an early FV model with air intake located on bottom?
If air intake is clogged with dust, then combustion chamber overheated and tripped FV system. The older heaters need replacement parts and new gas control valve, or entire heater must be replaced.

Replace gas control valve.
http://waterheatertimer.org/pdf/How-to-replace-water-heater-gas-valve.pdf

Copy following link for gas control troubleshoot by type of gas control.
http://waterheatertimer.org/How-to-troubleshoot-gas-water-heater.html#intellivent

Post question on Tank forum with more information about type of air intake and gas control valve and history of water heater
http://www.thetankatwaterheaterrescue.com/forums/forum3/

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

Look at label on side of product for Brand, model and type water heater.
Add a comment with that specific information.
Many of the questions I see are shortened to a few words.

If you have Reliance gas water heater with FV system, then clean air intake located on bottom of water heater using feather duster, or compressed air.
Other causes could be FV event that tripped TCO, and/or shorted out gas control valve.
Or you could have bad gas control valve.
Or dirty combustion parts.
Or all the above.

Inspect and clean air intake.on reliance:
http://waterheatertimer.org/images/Flame-trap-inspection.jpg
Troubleshoot Pilot
http://waterheatertimer.org/How-to-troubleshoot-gas-water-heater.html#pilot
Replace gas control valve:
http://waterheatertimer.org/pdf/How-to-replace-water-heater-gas-valve.pdf

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

Reliance is AO Smith.
Each gas control has identifying information on side of gas control valve. Make sure you order for NG natural gas or LP propane gas, since these are two different gas control valves.
Google search the gas control number and results will show.
Copy following links for more help:
http://waterheatertimer.org/pdf/How-to-replace-water-heater-gas-valve.pdf
http://waterheatertimer.org/How-to-troubleshoot-gas-water-heater.html#intellivent

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

Instructions for lighting Reliance 660 are located on the side of water heater just above the gas control valve.
If you are having other problems, read your product manual, or go to reliance for copy of manual, and read troubleshoot section:
http://www.reliancewaterheaters.com/lit/om.html

Unfortunately Rheem-Reliance does not post service manuals for their product. However other companies do post service manuals that might be similar to your water heater

Copy following link for troubleshoot service manual by type of gas control valve:
http://waterheatertimer.org/How-to-troubleshoot-gas-water-heater.html#intellivent

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

You posted under Reliance gas water heater
You installed a new gas water heater and are trying to light water heater using the piezo igniter.

Not clear is what steps you have taken so far, and which gas control valve is on the new water heater, and what lighting instructions say on side of water heater.
Also unknown if you bled air out of gas line, or if gas shut-off handle is rotated so handle is parallel with gas line.
Read instructions written on side of tank, open link below to double-check installation, and then add a comment with steps you have taken so far, and describe the type of gas control valve on water heater.
http://waterheatertimer.org/How-to-install-gas-water-heater.html

Reliance is Rheem
Replace thermocouple is best start point.
Example Whirlpool manual shows general replacement steps on page 22:
Buy thermocouple at hardware or home center. measure length before going to store.
http://waterheatertimer.org/pdf/Whirlpool-6510397.pdf

Utube videos show how to replace thermocouple

Many things can affect pilot:
Low gas pressure, Water or air or debris in the gas control valve, High-heat event causing ECO to trip requiring new gas control valve, burner and tubes needing clean-out, FV sensor tripped, loose or bad thermocouple.
Manual above shows general steps for doing some of these things, but service technician is probably best choice if thermocouple does not fix problem.

Gas water heaters require periodic maintenance.
If repairs cost more than $330, then buy new gas water heater and install yourself.
Use the old one for a solar collector.
http://waterheatertimer.org/How-to-install-gas-water-heater.html

Upvote the help.
And take advantage of fixya expert assistance live.
For a price, expert works with you while you work on water heater or any do-it-yourself project.
Fixya is always less expensive than a service call.

Reliance is Rheem
Replace thermocouple is best start point.
Example Whirlpool manual shows general replacement steps on page 22:
Buy thermocouple at hardware or home center. measure length before going to store.
http://waterheatertimer.org/pdf/Whirlpool-6510397.pdf

Utube videos show how to replace thermocouple

Many things can affect pilot:
Low gas pressure, Water or air or debris in the gas control valve, High-heat event causing ECO to trip requiring new gas control valve, burner and tubes needing clean-out, FV sensor tripped, loose or bad thermocouple.
Manual above shows general steps for doing some of these things, but service technician is probably best choice if thermocouple does not fix problem.

Gas water heaters require periodic maintenance.
If repairs cost more than $330, then buy new gas water heater and install yourself.
Use the old one for a solar collector.
http://waterheatertimer.org/How-to-install-gas-water-heater.html

Upvote the help.
And take advantage of fixya expert assistance live.
For a price, expert works with you while you work on water heater or any do-it-yourself project.
Fixya is always less expensive than a service call.

If you have error lights on gas control valve, then water heater has thermopile instead of themocouple.
Thermopile will generate more current to power electronics inside gas control valve.
Open following link to identify specific gas control and download possible service manual for that specific product.
http://waterheatertimer.org/How-to-troubleshoot-gas-water-heater.html

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7