Hi We have a Bosch 25e ranout of gas today delivery tomorrow. I have connected 9kg emergency bottle but Pilot light gone out and unit wont ignite. how do I restart?? Thanks Noel

refill the gas bottles and then if that doesn't fix it, get a technician out as it may be the pressure switch not opening the gas so that the pilot light ignites the burner

I believe this is a hydro-sparker pilot ignition then burner on when T-Couple/Flame Sensor acknowledges pilot lit.
W/O the signal feedback the Gas Valve will not open and light burner.
This is a Technician Service Job as you have insufficient knowledge to DIY this potentially dangerous LP/NG Control Valve/Sparker Assembly
I assume that lack of knowledge by your lack of a Manual for the Unit
You cannot force ignition on a hydro-sparker manually.

First suspect is air in gas line or dirty combustion parts.
Typical gas water heaters today suggest cleaning burner parts yearly, including bleeding air out of gas line.
Use a burner brush to clean tubes:
http://www.rvparts.com/product-85-91872

Other suspect could be faulty wiring or bad gas valve.

Check to make sure the flame of the pilot is hitting the thermocoupling. If not then you can use compressed air to clean the pilot port and relight and check again. If the flame is hitting the thermocouple, then it may need to be replaced.

The gas regulator might have failed , not allowing any gas to flow, or the draft regulator is failing not allowing the burnt air anywhere to escape and for no new air to enter for burn.

combi or standard if combi pressure too high and will be blowing off your high pressure release valve which would stop your boiler from igniting best of luck

In general, large button from gas valve push in & hold 20-30 secs at same time push electronic lighter/ignition button to light pilot. Remember to hold in only gas button. the pilot light heats up a thermo couple [u can see this in the flame] and when hot enough allows the main gas through and the pilot to remain on.
If not then either thermo couple not heated for long enough or
it may need replacing

get a long stick match, a flashlight remove lower inspection cover, find thermocouple and pilot light will be next to it,turn gas valve to pilot light and hold down,stick the match in by thermocouple till the pilot lights and hold valve down till pilot stays lit,this may take a minute or more,then release gas valve and see if pilot stays lit, if not retry,if it wont stay lit,the thermocouple is defective and needs replacement

First check your gas supply, gas in bottle or lines? I know, this is basic & I'm not having a shot at you, but you'd be surprised at how many times it gets overlooked.

If you do still have gas supply, evident by that low hiss when you hold the pilot feeder button in (you might have to lean in close to hear it), then you need to check that the piezo is working. This is the bit which produces the spark to ignite your pilot. You will be able to see it sparking at the pilot outlet when you push the button (if you're looking in the right spot).

Ok, you have gas & a working spark? Not sure which buttons to press?

You mentioned the manual no longer being in a helpful condition...do you know which of the 4 buttons, 2 taps, 1 slide control & 1 dial do what?
Well just in case, here we go in simple form... first button on the left is the pilot feeder (lets gas through the pilot), second button from the left is the 'ON' button, third from left is the 'OFF' button & the fourth from the left is the piezo ignite button (gives you that much needed spark!). The slide controls your flame (how much gas gets fed to it). The dial, below the pushbuttons & slide, controls how much water flows through the system which then helps regulate the heat. Make sure the taps on your gas & water lines to the unit are on. There you go...2 taps = gas & water supply, 4 buttons = pilot gas, on, off, piezo (spark), 1 slider = gas/flame control, 1 dial = water flow control.

Ok let's see if we can light it! Water & gas supply turned on, slider set about 25% from left, dial set roughly in the middle, push in button 1 (1st from left) & hold in for about 10 seconds, you should hear a very faint hiss from pilot area. Yes? OK, keep holding button 1 in & press & release button 4 several times until pilot lights, you may not see a difference but if you can't see it and it does light you will hear the faint hiss change to a soft fluttering sound as the flame consumes the gas. Still OK? if so then the next step is to push in button 2 quite firmly & then release button1 as well. If all works as planned you will shortly have hot water supply restored.

If the above has not worked then your hot water service may just need a service to clean everything up & maybe replace a few worn or excessively corroded parts. Otherwise ,if there are no blockages in supply lines etc, then it may be time to replace it.

You neglected to say how long you've had it.

Cheers, hope this has helped.

Dennis

Hi Welcome to fixit.com
Make sure the gas/propane is on and or working elsewhere in the house. If the piolet wont light ....and its a standing flame piolet ....its the thermocouple gone bad. Please rember to leave me some positive feedback ! Thanks !