Burner will not light

If its 1 blink every 3 seconds its normal operation.
Otherwise, this is the meaning of the various blinks:

No blinks = no poilet light (not enough power (in millivolts) to keep it lit.
2 flashes = insufficient voltage (in millivolts) to gas valve.
4 flashes = high water temperature (over heat sensor activated.
5 flashes = water temperature sensor failure.
7 flashes = gas control valve / thermostat failure.
8 flashes = Only occurs if the gas control valve or Temperature knob has been turned off And the thermocouple continued to produce electric power.
9 flashes = Combustion chamber temperature sensor open or shorted.
10 flashes = LDO occurrence was detected in the combustion chamber (contaminants).

I would check the thermostats, or possibly the temp sensor (if it has one). Sounds like the water heater is preventing the burner from turning on because it thinks the water temperature is too high (a safety feature to prevent the tank from blowing up, among others). If everything checks out, it may be the computer. The manual usually has explanations of the fault codes, otherwise I would try the manufacturer's website.

http://waterheatertimer.org/How-to-troubleshoot-gas-water-heater.html#intellivent

Call Bradford White or installer

Gene
h

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

You can reset the code by turning Gage all the way up highest setting count to ten turn it to hot could to ten then turn to pilot count to ten and then turn it to desired temp burner should come on. Saves lots of money and time

Raising temperature above 120 degrees requires service call.
Or change dip switch settings and risk voiding warranty and causing service call expense.
http://waterheatertimer.org/Troubleshoot-Rheem-Tankless-water-heater.html#temperature

Earliest versions of Rheem tankless 2006-8 let you set temperature up to 140 degrees F using remote.
However the hotter setting caused error codes because the burner cannot keep up with both high temperature and large volume of hot water rushing through pipe. Especially in winter with cooler incoming water that must be heated more to reach temperature set point.
The burner simply cannot keep up.
So Rheem changed maximum temperature at remote control to tepid 120 degrees, which is not hot enough for folks wanting hot shower, or folks filling whirlpool tub because water in tub cools before tub fills.

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

Crossover, low hot water flow, low water pressure, sediment in water lines or heater, heat exchanger needs to be de-limed, water filter needs to be cleaned, water heater temperature set too high, incoming water temperature too high or too low depending on model, MUD or PUD districts with pressure spikes, dirty faucet aerators, loose wires, bad sensor, faulty PD-board, bad venting, dirty burner and combustion parts, etc.

Crossover
http://waterheatertimer.org/Crossover.html
Clean water filter monthly, de-lime tankless yearly
http://waterheatertimer.org/pdf/Tankless-maintenance.pdf
http://waterheatertimer.org/pdf/Rheem-De-lime-tankless.pdf
No error code:
http://waterheatertimer.org/pdf/No-Error-Code.pdf
Overcoming fluctuating temperatures:
http://waterheatertimer.org/pdf/Bosch_Overcoming_fluctuating_temps.pdf
Resources:
http://waterheatertimer.org/Troubleshoot-Rheem-Tankless-water-heater.html

Depends on gas control valve, and if cause is overheating high-limit event or FVIR flammable vapor event.
Turn off water heater when using flammable vapors, clean burner parts to prevent overheating.

1) GSW Residential power vent gas water heater with FVIR system:
Some models have intelli-vent gas contol
Others have robershaw gas control with auto-reset

2) Parts manual shows #15 'auto-reset' high limit switch on the blower
http://www.gswpartsonline.com/model/27484
http://www.gswpartsonline.com/schematic/137/view

3) Possible manual:
http://www.gsw-wh.com/pdfs/GPD135NInstall.pdf
Shows resettable lockout page 15
Water temperature must be 120 degree F or lower for reset. Unplug power cord, and then plug back in and wait 15 minutes or 60 minutes depending on gas control valve.
Some intelli-vent controls must be replaced when 195 degree high limit event locks out the water heater.
If high-limit lockout repeats, then gas control must be replaced.
Also clean burner parts, air intake, and make sure flame is clear blue. and not yellow-or-orange.

4) Intelli-vent service manual might apply to your water heater:
http://waterheatertimer.org/pdf/Intellivent-service-manual.pdf

If FVIR flammable vapor event locked out heater, then unplug heater and plug back in.
Immediately press two temperature buttons. Wait for green light to blink. Release buttons.
Page 34 in troubleshoot chart.

5) Take a moment and rate answer:
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.

This condition can be caused by 4 different problems, or combination of these problems.
Good indicator would be to check temperature of water inside tank.
Put bucket under TP overflow tube and release water into bucket, then use cooking thermometer to gauge temperature. Stand back from scalding water that can shoot out of overflow.

If tank temperature is 120-130:
1) Crossover is suspect:
http://waterheatertimer.org/Crossover.html

If tank temperature is low:
2) Bad gas control valve thermostat is suspect.
I believe Rheem 41VRP50N has Honeywell or White Rodgers electronic gas control valve.
Open following link to identify gas control thermostat and see typical error codes.
http://waterheatertimer.org/How-to-adjust-temperature-on-water-heater.html#Honeywell
Replacement gas valve can be purchased from Rheem.

3) Combustion parts and tubes need cleaning, and bleed gas line for air and water contaminants.

4) Water heater has sediment build-up coating burner transfer surface and covering thermostat.
http://waterheatertimer.org/Clean-sediment-out-of-water-heater.html
Year of manufacture for Rheem water heater is 2nd two digits of serial number, so XX03.. would be 2003.

Add a comment and say what you did to solve problem.
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.

2 flashes = high water temperature (the water heater comes set at 120, and you can set it lower or higher)
3 flashes = sensor failure (temperature sensor similar to a thermostat on regular water heater)
4 flashes = upper element
5 flashes = lower element
Links below are for Whirlpool manuals
http://www.whirlpoolwaterheaters.com/support/Manuals.aspx
http://waterheatertimer.org/pdf/Whirlpool-energy-smart-electric-manual.pdf

The water heater is working right now.
If the elements go out, they are available at any hardware store.
The temperature sensor is easily replaced and can be ordered from Whirlpool.
You might want an extra temperature sensor on-hand so repairs are not delayed.
Link below shows the product in detail.
http://waterheatertimer.org/Whirlpool-Energy-Smart-electric.html
Let the water heater do its job until it fails.

Here are a couple things to look for:

1) flashing burner light - a flashing burner light indicates the unit is getting an error code
common error codes:
A. continuous flashing - ignition failure or abnormal combustion; look for visible water in the machine indicating a leak, check gas pressure, debris or buildup on flame rod/igniter plug, or clean unit with compressed air
B. 3 flashes - error 16, abnormal outlet water temperature; typically this code indicates you'll need to descale you unit
C. 4 or 5 flashes - exotic error codes; you should contact Noritz technical support to deal with these codes

2. If there is no flashing code, try increasing the hot water flow. In the summer time you typically use less hot water; this can result in intermittent operation of your tankless heater. Increase water flow by either: A. cleaning your showerhead and removing scale deposits B. widening your flow restrictor C. Remove your flow restrictor in the showerhead

3.If none of these resolves your problem, you probably have debris in your flow sensor. Contact Noritz technical support for a walkthrough on removing debris from a flow sensor.