Warning light on Bosch Worcester Junior 24i

by **kokoshka** » Fri Jun 08, 2007 12:21 pm

I turned ch off a couple of months ago for the summer. Hot water was ok after that until I tried to put the heating on again. Heating would work for half an hour, then warning light would flash rapidly, and both hw and ch would fail. The only way to get the boiler to light after that was to turn off at mains for about 20 mins, then try again, but without ch. Since then, the problem has worsened, with the light coming on and flashing without attempting to put heating on. Sometimes the system runs ok for hot water for a couple of days, but more often than not, it fails after a couple of minutes. The boiler is about 2 years old. Any ideas?

by **htg engineer** » Sat Jun 09, 2007 4:54 pm

if you have the boiler instructions look in the fault finding guide, the flashing light normally has a sequence to tell you the fault (the number and quickness of the flashing light) sound like its going to flame failure, this can be electrical, a problem with the gas supply or something simpler like the flame sensing electrode.

Almost impossible to diagnose without seeing the boiler. Will watch for your reply if you find out what the fault finding guide says.

by **kokoshka** » Sun Jun 10, 2007 7:21 pm

Hello, thanks for the reply. I do have both the users manual and the more extensive engineers manual, but can't find either! I downloaded the short booklet, it describes 2 ways for the warning light to flash: Once a second, for boiler overheating or ignition lockout, or as is most probably the case with my boiler, 5x a second ( it's difficult to count that fast!), indicating an airflow fault. Electricity to gas valve will be interrupted if controls don't detect correct airflow. I have noticed that the radio crackles sometimes when the boiler is faltering, and that even when there is no demand ( c/h off, taps off, but in the few minutes following hot water demand), the boiler tries to re-ignite. This is consistent with the advise in the manual, which indicates that the ignition will try to re-ignite after 5 minutes. The engineers manual is much more thorough, offering a menu-type diagnostic chart, but frankly, I found it a bit daunting. I'll keep looking though, I really don't want to pay Bosch Â£150 for a callout. Thanks again.

by **kokoshka** » Mon Jun 11, 2007 7:55 am

...a pattern has definately established itself...when I get up in the morning and turn on the hw, no ch, the radio crackles with electrical interference, and the boiler fails. In order to get the hw to work, the boiler must be turned off at the mains for some time.

by **sparx** » Mon Jun 11, 2007 7:30 pm

Hi, have had this recently with same model, although heating was off for summer the boiler would not light reliably, fault traced to low pressure on heating. The pressure gauges are not very accurate (cheap & nasty), I put some more pressure in system until gauge showed just under 2 bar & away it went!
The method of recharging involves the use of the key stored inside the bottom removable panel, see hand book for use, it basically goes into a valve under boiler and you use a rotary black knob next to it to add pressure, If over done then open bleed screw on a rad to reduce,
I think thats it but I am only a leckie fault finder not a plumber/htg eng,
regards SPARX

by **htg engineer** » Tue Jun 12, 2007 2:56 pm

An airflow fault is a problem with the flue, fan or air pressure switch. Knowing abit about boilers would help. If you turn the heating on can you hear the fan ? or can you hear a buzzing noise ? if its buzzing the fan could be getting stuck, sometimes can be freed.

If the fan is running it may not be running at high speed or enough to operate the air pressure switch. OR the air pressure switch could be faulty.

As these are room sealed appliances the outer case should not be removed by anyone other than a CORGI registered gas fitter. So it wouldn't be right for me to ask you to remove the boiler case.

I would call a heating engineer out, try someone that works outside of their full time job, to diagnose the fault should only cost about Â£45 (thats all I charge), if it cant be repaired you will need to pay for parts and labour.

by **carpman** » Wed Jun 20, 2007 6:08 pm

I had the same problem! Traced the fault to a relay on the pcb board,
you will see 3 relays together 2 thin white ones and a orange one
its the middle white relay Tyco v2309-A1024-A802 6A/250V 24V!
Sourced a new relay from a electronics shop for Â£12.60 fitted new relay boiler now working perfect!
Or you can just get the whole pcb board replaced?