My boiler keeps cutting out to a red light when the heating is on. I also have a problem that the hot water keeps going cold and often has to be run for a few minutes before it warms up again!

Recently been serviced (1 month ago) with a sensor replaced as this was meant to be the problem with the red light and hot water!! Help please!!

Fed up mum of three, October 2008

Did you sought the problem out who’s advice did you use?

Lee, January 2020

big thanks Rob, was on the verge of calling out a plummer - on a bank holiday weekend - when all it needed was to press the 'little red button '

Steve R, April 2017

Philip brown was right you actually helped me thank you very much. I did as you said and my problems solved 100% thanks again👌🏽😊.

Kamran A, August 2015

Some of these answers are frightening. Removing combustion panel to get it to work etc. That panel maintains the "room sealed" aspect of the boiler and as such the boiler should never be operated with the panel loose.

I'm all for people trying to sort there own problems however when it comes to gas related appliances you must have Gas Safe Registered engineers working on them. Yes this comes at a cost but these people have went through years of training to understand the safety side of gas appliances. Please please please be more vigilant. No point saving a few quid to only end up putting people in danger by negligence

Gary - Registered GSR Engineer, March 2015

Sabre 35he

Hot water ok, heating starts ok but boiler stops after about 30 second from cold.
I think the overheat start cuts it out. Possible that the heat exchanger needs cleaned.
Would you know if there are filters fitted to the flow and return valves and if so they could cause overheating in the exchanger.

bal, February 2015

Cutting out after 10 mins or failing to re-ignite is a very common fault with the Sabre HE boiler. It's easily fixed.
Switch off the boiler at the mains. Take the main cover off. Unclip the the front cover and remove it. Remove the three screws holding the faceplate to the condensing chamber. Remove the faceplate. This is to allow access through which to remove the Venturi valve. Remove the tube to the Venturi valve (top one). Feed a flexible thin wire through the venturi valve to prevent it dropping when unscrewed. (I used a small length of garden tie.) Unscrew the retaining nut. Push the venturi valve along the ducting to the access plate hole or try and grab the end of the valve with a claw grip while pushing the wire.
Clean inside the valve. It only takes a minute piece of dirt to prevent the valve from working. Reassemble using the same method as removal. Job Done.

Philip Brown, March 2014

Found the little red button and it worked. Thank you for the tip. Cheers. Martin

Martin, November 2013

Im having trouble too with the hot water it seems to stay on for a couple of mins then go cold. After about 10 - 20 secs it start to warm again as you can imagine very frustrating has anybody got any ideas? is the technical helpline worth calling/ Im no plumber.

Dave H, April 2013

some of these reply messages are really frightening as people are breaking combustion chamber seals and MUST only be done by a gas safe engineer !!!!!!!!!!!
if not done correctly it could lead to carbon monoxide products entering the room !!!!!

a registered gas safe engineer !!!!!, February 2013

I found mine to have the siphon housing blocked with limescale, this wouldnt allow water which would normally flow down the condensing pipe to flow.
Ultimately the siphon filled with water and the float ball then cover the venturi pipe port.
I just had to take the siphon off, completely clean it of limescale, blow through the condensing pipe to ensure its not blocked then refit the siphon and run the boiler.

Dave B, January 2013

I've had issues with a Sabre 29 HE combi boiler since moving into a new house that had one installed. Initially in the summer time we only used it for instant hot water. It quickly developed a problem of cutting the flame out about 8 seconds after firing up for the hot water demand. This turned out to be a faulty ignitor/flame sensor.The igniter was creating the spark and firing up the flame, but the flame wasn't be sensed and consequently the gas valve was being closed again as no flame signal/ignition confirmation was being sent back to the board. Turns out the ignitor and flame sensor are one in the same thing. Initially I thought they would be seperate items. Replacement of the ignitor/flame sensor fixed that issue. The second issue we had was when we tried to use the central heating. I noticed that the water pressure was rising to 3bar and over, triggering the overpressure release valve, and evacuating the system to the outside pressure release pipe. I would then have to charge the water pressure back to I bar before it would reset, only for it to do the overpressure thing again about an hour later. After some research I thought the expansion vessel had failed and that was casuing the overpresssure issue. It turned out that the stainless braided flexible pipe going to the expansion vessel was blocked with hardened sludge. Cleaning this sludge blockage away and making sure the expasion vessel was charged to correct air pressure resolved the over pressure issue. Finally I also noticed that when central heating was running it often cut out after say 30 mins running and went into the 0.5 sec green light flashing mode, only to start up again a few minutes later. If set to higher central heating temperature settings it would also make a kettling sound and the go into lock out mode (red light). The over temperature switch on the pipe coming directly from the main heat exchanger that runs down the right hand side of the firebox would have to be pushed back in to reset the system. This overtempraturing happened even more quickly when direct hot water was required. The hotter you set the DHW, the quicker it would lockout and start running cold water to the hot water taps. Before starting to buy replacement parts I would advise that the system be stripped down and internal piping examined for sludge blockages. I did this and found that the outgoing pipe coming from the main heat exchanger had become serioulsy restricted just before entering the by-pass cassing. This had been the cause of the kettling and overheating. As the pump was trying to pump the water around the system and through the heat exchanger, the restriction causing the pipe narrowing was slowing the passage of water through the heat exchanger to such an extent that it was kettling and causing the overtemparture lock out. After clearing these blockages and checking the pump was functioning properly, the system worked without anymore issues. Piping hot central heating and DHW.

GBarker, February 2012

hi my saber lights up when i turn the water on after 2 minutes it cuts off i have cleaned venturi pipes straight one no problems the 90degree one i blew it out with compressed air line as this boiler is in my tyre garage i have a compressor i used a bicycle pipe to fill the air in the expansion tank fan comes on but the burner doesn't light how ever if i blow in the top clear tube connected to differential valve it will light up but cut out again my email is please help

redcar, August 2010

Same here, cleaned out Venturis so go get it guys LOL
PS. anyone having problems with the timer swith not working on AUTO?

James Scotland., June 2010

i had the same problems as above.

sabre 29he runs the central heating for 10 mins then cuts out and displays red led.

actual symtom was, CH would run until it got upto temp then cut off, but the boiler wouldnt re ignite when the temp dropped again. i bought a new NTC sensor off ebay for £5.80, but it didnt cure the fault.

i discovered that the boiler would reignite when hot if i undid the clips on the siver panel with the glass window and it sucked some air in. further to that i discovered it was the pressure switch at the top which wasnt operating when the fan started and the boiler wanted to ignite, but would if the silver panel was unclipped.

i had found a thread on this site that said 'if the venturies were dusty it would cause this fault'. so i cleaned the venturies with a cotton bud. the lower venturie (on the fan housing in the top right of the boiler connected with clear tubes) is a straight pipe, so is easily cleaned with a cotton bud, and the cotton bud was dirty from cleaning this. but the problem comes with the upper ventury as this has a 90 degree bend inside the fan housing, after cleaning with a cottonbud i reassembled the boiler and now it wouldnt fire up at all.

i had to remove all relivent screws holding the hood and fan motor, and pull hood out about 3" so could put two fingers in the fan housing and take the upper ventury out (after unscrewing the brass retaining nut) and i discovered a blob of jointing compound just on the inside edge of it. this is down to poor assembly at the factory. the ventury was cleaned and boiler reassembled.

the boiler now fires up much much quicker then it ever did. meaning hot water as soon as the tap is switched on and no more red led.

toasy warm, north lincs., September 2009

i had the same problem with my boiler cutting out to a red light. after fitting a new NTC SENSOR wich cost £12.65 all was well. ihave a sabre/vokera he29. part number 10027352. the location of this is on the top right hand side inside the part of boiler that has a round glass window to view burner. dont forget to disable from electric and drain system of water first.hope this is helpfull as gas engieers certainly do know how to charge you a small fortune

carl, January 2009

Hi there - I had the same problem by the sounds of it but I have found the answer to fixing it! In my case, the boiler was firing up, radiators were coming on etc but then approx. 30 mins later, as the heat reached a point and the thermostat turned the flame off, it was seizing up before it could re fire and the red light was coming on. I would then have to reset the system by turning it off then on again but the same problem would occur a few mins later. I got a CORGI registered plumber out who did loads of tests but was flummoxed by the problem as the boiler would work fine with the internal cover off (exposing the ignition to more air) At first he thought it must be a problem with the fan or the thermostat but after nearly 3 hours of testing we discovered the problem: A very VERY small amount of dirt had built up on the inside of the 'Venturis'. These are little pipes that are attached to the fan (on my SABRE HE 29 they have clear air tubes attached to them) Apparently, despite the grime being almost invisible to the eye, if these are even slightly blocked will affect air pressure going into the ignition area and stop ignition working. If this sounds like the same problem, get your boiler repair person to clean these venturis out thoroughly with cotton buds. It worked for me! Good luck!!

Glenn, October 2008

Hi. Just in relation to this - I'm having exactly the same problem as the fed up mum of three. I can get the boiler going again by switching the boiler off and on again at the main switch but after an hour (max) the light goes red and it needs to be restarted. This wouldn't be a major problem but obviously the timer isn't able to switch heating on if the system has locked out so we're waking up in a very cold house!
Rob - I wanted to ask re your answer. Does your suggestion solve the problem for a long period of time or just until the next lock out?

Glenn, October 2008

Hi, Who did you get to service your bolier? my sabre keeps playing up the same but I know how to fix it but im starting to get fed up with taking the cover off to reset the problem.
If you want to fix yours all you need to do is un do the 3 screws on the bottom and take the white cover off. once you have done this there is a big silver pannel with a little glass window on it you need to take this silver cover off I would suggest with the boiler turned off. once you have taken this cover off by in clipping the two clips at the bottom of the silver pannel look on the right side for a copper pipe with a block on it with 2 wires going into it on there will be a little red button press this and it will click if you put the covers back on and turn the boiler back on this should solve the problem.
Hope this helps

Rob B, October 2008