Patio Heater won't light

I don't recognize the models number, if your water heater is an electric, check the two-pole circuit breaker in the distribution panel to make certain it has not tripped. If it has, try resetting it. If it will not reset, the heater element is probably bad. If the breaker has not tripped, either the thermostat(s) or heating element(s) are bad.
If it's gas, there are several problems that can cause a heater to not start. First is the pilot lit? If not, try holding the gas control down in the pilot position and light it using a match. (The instructions are on a label on the side of the heater). After the pilot lights, turn to "on" position and it will start to reheat the tank. If the pilot will not relight, either the gas control is failed, or (more likely) the thermocouple has failed. (The thermocouple is a very small copper tube that screws into the gas control and the other end is positioned in the flame of the pilot (it monitors the pilot flame to make certain the pilot is burning and only if satisfied, will allow the gas control to turn on and heat the water in the tank).
Hope this helps.

Is flame clear blue or yellow?
Yellow flame, clean the flame arrestor screen
http://waterheatertimer.org/How-to-troubleshoot-gas-water-heater.html


Flame is blue:
Low gas pressure.
Bad gas control valve.
Dirty combustion parts.
Clean the water heater parts and catch up on maintenance.-
http://waterheatertimer.org/How-to-troubleshoot-gas-water-heater.html#intellivent

Gene

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

does the pilot go out when you let off the button? Or does the pilot not light at all?

If you dont get any gas at all to the pilot the the gas valve is bad.
Of you get a pilot light that goes out when you let go of the button then the therno couple is not reading the flame (needs adjustment so the pilot flame touches it)
did you kink the new thermocouple? or over tighten it at the gas valve.
if it was kinked its now toast,cant straighten them. If kinked and starightened the fluid inside has broken the inner seal and wont work.

What band and type water heater do you have? And about how old is the water heater? Add a comment with more information.

Following general information applies to tank-type residential water heater.
If pilot light is working, then thermocouple is good. Otherwise, if thermocouple was bad, or fallen out of place, then there would be no pilot flame.
Carefully read instructions for lighting water heater located on front of tank ... make sure you have the gas control valve set to ON.
At this point, troubleshoot varies widely depending if your water heater is older and air enters front of heater, or if water heater was made after 2007-9 and has sealed combustion chamber and FV system.'
Troubleshoot also varies widely depending if you have power vent and which type of gas control valve.
Copy following link for troubleshoot by type of gas control valve:
http://waterheatertimer.org/How-to-troubleshoot-gas-water-heater.html#intellivent
Also post detailed question on pro water heater forum.
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

Make sure thermocouple tip is seated inside the burner flame.
Make sure thermocouple is not overtightened. Finger-tight + 1/4 turn.
If the pilot lights, then ECO energy cut off is not tripped, but gas control valve might be bad.
Check color of pilot flame: it should be strong and clear blue.
If pilot flame is weak, or color of flame is yellow-orange: Clean pilot orifice and burner and combustion parts on yearly basis.
Clean air intake screen if applicable.
Increase air supply to water heater. Open a window and see what happens.
Check for adequate draft going up chimney using match under vent hood to see if smoke drafts immediately upwards.
Bleed air out of gas line.
Check gas pressure.

Open following links for troubleshoot resources:
http://waterheatertimer.org/pdf/Pilot-light-will-not-stay-lit.pdf
http://waterheatertimer.org/pdf/Pilot-outage-troubleshooting.pdf
http://waterheatertimer.org/pdf/Vent-spillage-test-atmospheric-gas-water-heater.pdf
http://waterheatertimer.org/How-to-install-gas-water-heater.html#troubleshoot

Better description is needed. Add a comment.
Do you have tank or tankless water heater?
What brand heater and what model shows on label?
If tank water heater, what does gas control valve look like? Is it electronic?
Open following link to help identify tank-type gas valve.
http://waterheatertimer.org/How-to-adjust-water-heater-temperature.html
Does pilot light start up and not stay lit, or is there no flame whatsoever?
What color is the flame?
Are you using piezo igniter or a match to light pilot?
Is there a power vent sitting on top of unit?
What happens when you get more fresh air to unit?

1) Maybe the thermocouple is bad. Or thermocouple is mis-aligned and not sitting in the flame.

2) Probably the technician should have cleaned the combustion parts.

3) Tank-type and tankless water heaters require cleaning on a yearly or semi-yearly basis. This action prevents lighting problems, and help prevent ECO events and that require replacing gas control valve.
Cleaning and general service including cleaning burner, cleaning air intake if that applies, checking for proper venting and vent obstructions, adequate air supply, backdraft, testing thermocouple etc.

4) IF you have tank-type water heater, and do not have electronic gas valve or power vented water heater, the following troubleshoot walk-thru is very good:
http://waterheatertimer.org/pdf/Pilot-outage-troubleshooting.pdf
Example photo showing parts for gas control valve.
http://waterheatertimer.org/images/IMG_9146-gas-control-thermo.jpg

Add a comment for more help

So are you saying that the first initial lighting of the pilot, without turning to on, works o.k., good flame etc, ? If not sure, try lighting pilot only, and leave setting at pilot only, and see if it's a good flame, and get back to me.

if water heater will heat a tank of water before the pilot light goes out you need to replce the gas thermostat