Would high winds and rain cause pilot light on a rannai tankless water heater to go out?

SOURCE: Bosch 125 Tankless Water Heater - Water not hot enough

Sounds more like the venturi in the watervalve of the tankless water heater is clogged. I would recommed rebuilding it and paying close attention to properly relubing the pushrod and cleaning the venturi.

SOURCE: burner will not light

Try this web site!
http://www.protankless.com/BoschProHome/GasProducts/BoschGWH425HN/tabid/506/Default.aspx
Copy & Paste to Google search engine.

SOURCE: lighting the pilot light

The steps involved can vary slightly depending on your furnace model and pilot valve type, so if possible try and find the instructions inside the furnace door cover or in the instruction manual. This is for a gas fired furnace, but applies to any gas-fueled appliance including water heater. Two of the most common types of pilot valve body assemblies either have a red reset button and a gas valve or no reset button and a valve knob that can be depressed. But whichever type you've got, if you have an older model furnace with a standing pilot (flame is lit all the time) then this is the basic procedure.

• Turn you thermostat to 80 degrees or to a setting that will demand heat. Make sure the thermostat is in "Heat" mode.
• Go to the furnace and find the pilot valve. The pilot valve body is a box shaped device into which the main gas line will run and is located near the gas burners. It will usually have a gas **** or valve knob that reads "On, "Pilot" and "Off." Locate this gas **** or knob.
• Turn the knob or gas **** to the "Off" position and wait about 3 minutes for any residual gas to clear away.
• Find the pilot. It's located near the gas burner tube assembly in the furnace.
• Get your match or lighter ready. Sometimes the pilot is hard to reach. If possible, try and use a long fireplace match when you light it. If you don't have a fireplace match then a butane BBQ grill lighter works well too. If you don't have that, then you can fasten a match to the end of a stick when you light the pilot

• If you have a pilot with a red Reset button, turn the gas valve from "Off," to "Pilot."
• If you have a pilot with no red button, turn the knob from "Off" to "Pilot."
• Place the lit match or ignited lighter tip at the pilot and depress and hold the button or depress the knob as appropriate. Depress the button or knob for about 30 seconds. This maintains gas flow to the pilot until the thermocouple gets hot enough to open the main gas valve.
• Once the pilot stays lit, slowly release the button or knob and turn the gas **** or knob from the "Pilot" position to the "On" position. This will ignite the burners and keep the flow of gas supplied as required for the burners as called for by the thermostat.
• If the burners fail to ignite then it may be because the thermocouple did not get hot enough to open the gas valve. Wait a few minutes and then repeat the above procedure. This time hold the red reset button or depress the knob for about 45-60 seconds.
• Once the main furnace burners ignite, adjust the thermostat to the desired setting.
• If you've followed the previous steps on lighting the pilot and it still does not light after, or will not stay lit, then you probably have a problem with the thermocouple or an adjustment needs to be made to the pilot. You'll need a furnace service technician to replace or repair these parts. You may find that the pilot lights, but it is an anemic looking flame. That's a different problem we'll look at in the next section.
  
• If the pilot lights but the flame is a weak yellow flame, it will not get hot enough to heat the thermocouple to its set point allowing the gas valve to open.
  A natural gas flame should be a bright blue with the tip of the flame having just a tinge of yellow. A propane flame should have a bluish green flame with a tinge of yellow at the tip. The flame should be strong enough to hit the thermocouple tip about 1/2 inch from the tip end. If the flame is weak or shaky looking, check to see that a breeze or draft is not blowing on it. Adjusting the Flame
  There is usually a small screw on the pilot valve body that will adjust the flame. You may have to refer to the manufacturer's instructions to find the screw. Turn the screw as needed to adjust the flame throw. Yellow Flame
  A yellow flame is caused by lack of air and incomplete combustion. It can be caused by a dirty pilot tube tip. Split Flame
  This is caused by dirt in the pilot tube. Take a needle or small nail and gently clean the tube. Flickering or Wavering Flame
  A flame that flickers is usually caused by a draft.
  

SOURCE: Tankless water heater pilot light will not stay on

It is most likely the water valve stuck open, telling the controls to heat water, that it thinks is flowing through it, but without actual flow it overheats. Depending on how comfortable you are with taking it apart yourself, you could open the valve to see if it just needs cleaned out, or if you have a ruptured diaphragm or some other cause.

Ned C Cook

• 3433 Answers
• Posted on May 06, 2009

SOURCE: no hot water, pilot light lights but no burner ignition

Thermo coupler may be defective. it controls the main gas valve by closing main if pilot is out. make sure thermo coupler bulb is positioned over and near tip of pilot flame, but not in the flame. Thermo couplers are inexpensive and easy to change out.