Boiler Breakdown Sticky

[Dotty]

For hints, tips and secrets of boiler breakdowns.

 

[neily01]

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!

 

[Whyme]

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).

 

[Whyme]

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..

 

[neily01]

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.

 

[R1CKY]

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.

 

[zeebeedee]

Worcester 230. Central heating problems. No voltage on x3 pin 4 violet wire. Divertor microswitch at fault.

 

[neily01]

Vaillant f75! Why bother we all no this one lol

 

[zeebeedee]

Glowworm micron poor Fga readings if everything looks good , faulty fan slowing with age.

 

[zeebeedee]

Vaillant f75! Why bother we all no this one lol

What's that then? Don't work on valiants much.

 

[Whyme]

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...

 

[neily01]

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.

 

[Whyme]

What's that then? Don't work on valiants much.

normally a pressure sensor fault , they get choked with crap.

 

[neily01]

What's that then? Don't work on valiants much.

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.

 

[Ollieg]

Gledhill System mate 3 with no hot water. Check the make up tank has enough water in it.
A lot of people miss this.