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Boiler Breakdown Sticky

View the thread, titled "Boiler Breakdown Sticky" which is posted in Boiler Advice Forum on UK Plumbers Forums.

Ideal mini boiler goes through the sequence but no ignition, check for 240v at the dark blue wire leaving aps if so faulty ignition pcb had lots!
 
Posted before but if you have a glowworm cxi and the fan pulses on and off along with the display after working on it ...get a hairdryer and heat up the pcb because theres a dodgy capacitor on the board that freaks out when cold......i thought tech were winding me up but it works. (if it doesnt the pcb's knacked).
 
Fit a vailant 937 recently and when the cold tap was turned on the boiler pump would kick in but not fire, like if a hot tap had been opened briefly...apparantly the aquasensor picks up negative pressure sometimes even through the cold so..get to the diagnostics by pressing the i + - buttons simultaneously. To access the second level diagnostic codes scroll through to D.97 press the i button scroll to 17. Press and hold the i button untill it returns to D.97. Then you wil be able to access second level diagnostics.....D.88 (adjust the sensitivity of the aqau sensor for water hammer..0=1.5l/min and no delay..1=3.7l/min with 2s delay........i adjusted with a delay, Good times..
 
Vokera Unicas and mynute he fault code 73 return thermistor faulty. The return thermistor will have corroded because the silly clip holding the flue thermostat to the conveyor has cracked the conveyor. New conveyor and thermistor easy enough done.
 
If you've narrowed down a fault to two suspect components, the faulty one will be the one you choose not to order.

Strange intermittent fault on an Ideal Icos/Isar/Istore? Check the rear of the heat exchanger, they tend to melt and can play buggery with the wiring loom.

Ferolli Modena 102 and similar firing up for seconds at a time with NO DEMAND is caused by faulty thermistors usually. Doing the same with demand, is usually caused by the venturi failing. DO NOT REMOVE unless you are 100% sure or have a replacement, 9 times out of 10 it will turn to a little pile of dust as soon as you touch it!

Ariston Microgenus, usually give a fault code relating to the air pressure switch, most of the time its the fan. They seem to be running perfectly, but they slow down with age and don't spin fast enough to operate the APS.
 
worcester 30cdi greenstar if you cant get a good co2 reading ie all over the place its usually the (not sure of the component name) little flap just after the fan, it opens and shuts when the the fans running...
 
Not quite the same but will go with it,poor hw with gled hill 2000 keep pressing sw2 button at the top of pcb until hw temp value is being read. If it reads h85 and the plate is cold then new hw thermistor required.
 
zeebeedee said:
What's that then? Don't work on valiants much.
Click to expand...
Sorry missed that vaillant water pressure switches detect system pressure but also look for a 0.3 bar spike when the pump first kicks in, if it doesn't detect the spike thinks its a pump failure. So if the pumps running but getting f75 it's a blocked up pressure sensor. Bad position on the old models bottom left now top left on the new models.
 
Ahh Gledhill! If you are ever unfortunate to come across a Gledhill Gulfstream, turn around and walk away! I'd rather try and resolve the North Korea crisis that work on one of those abortions!

DHW diaphragm on a Gionnani diverter valve not making contact with the microswitch, bit of plumbers mait and a 5p coin stuck to the top hat on the pin works as great temporary fix until you can make a permanent repair.

Heatline Vizo and similar. Hot water not working will most likely be caused by the diverter cartridge leaking into the motor. Turn the power off at the mains before you touch it, as they can blow fuses on the board, sometime the board itself, when they are moved with water in them.
 
Glowworm flexcons flow flexi bottom left hand side start leaking when the crimp clips start to get loose. Replacement flexies have jubilee clips rather than crimp clips
 
neily01 said:
Sorry missed that vaillant water pressure switches detect system pressure but also look for a 0.3 bar spike when the pump first kicks in, if it doesn't detect the spike thinks its a pump failure. So if the pumps running but getting f75 it's a blocked up pressure sensor. Bad position on the old models bottom left now top left on the new models.
Click to expand...

Changing one of these on Monday. Vaillant also say there is a filter that can be accessed and cleaned if you remove the rubber flow hose.
 
croppie said:
Changing one of these on Monday. Vaillant also say there is a filter that can be accessed and cleaned if you remove the rubber flow hose.
Click to expand...

if its an old one the part will be on the bottom left in the brass block "rubber hose type". ifs its newer it will be behind the air exhaust to the left just before the pipe goes into the main heat ex " copper connections no rubber hoses"...its a black part that has a little pin plug attached..if you undo the rubber flow hose then make sure youve got a jubilee clip to make good after. (just crunch the hoses croppie to get rid of the crap around the system).
 
Last edited by a moderator:
Vaillant also say there is a filter that can be accessed and cleaned if you remove the rubber flow hose./QUOTE]The filter is is plastic and i have found it very hard to remove to clean. You are better of chucking the whole piece in a bucket of descaler.
Click to expand...
 
Ideal optia,basically a early condensing classic. Water staining and rusting on the inside of casing running down centre of the boiler. HAd two o these with good fga readings of about 20ppm co and 0.00 ratio so thought it could not be inner flue! Wrong! break the top section of secondary hex and withdraw to find the pipe adaptor corroded through leaking all over the back of boiler. God knows how the fga wasn't going crazy?
 
Gloworm betacom 24/30c short cycling..... Check flame electrode hasnt bent into burner so flame isnt recognised.

No ignition on ferroli tempra, remove a wire from aps and if fan kicks and ignition commences in you know you have a sticking aps.
 
IDEAL LOGIC+ you can find the last 10 faults and also current reading, flow rates, temperatures etc in the installer settings.
all you have to do is turn both dhw and ch potetiometer knobs to minimum and hold the reset for about 2 seconds
 

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