Vaillant Turbomax 828 (628?) combi - fault found and fixed - for reference

eeyore.is.here · 2012-08-28T16:28:23+00:00

Just for reference, in case anyone has the same problem, my Vaillant non-co=ndensing Turbomax 628 or is it 828 ? combi, now 9 years old, has been a lit=tle intermittent lately, with hot water sometimes not coming through. Howev=er, it always fixed itself quickly. Not today.The diagnostic code was S.33 wich points to the fan/pressure switch.Indeed I couldn't pick up any voltage to the fan at the circuit board conne=ctor when I turned the hot water on or tried the CH. The pump ran, the dive=rter valve diverted etc.The diagnostic booklet flow chart simply tells you to change the pcb at thi=s point.I prised the plastic back covers off the pcb had a look. The central (mains= voltage) area smelt of ozone. Ozone meant sparking, but I couldn't figure =out what might be sparking. Well a few attempts at turning a hot tap on and= tapping things soon provided an explanation - greenish-blue arcing inside =one of three large relays (transparent cover).=20Prising the transparent cover off allowed access and bit of a scrape of the= changeover contacts later (using wet and dry) and the relay closed without= continual fizzing and arcing (a slight spark but that's normal for an indu=ctive load like a motor). However, still no 240V at the fan motor connector=!I isolated the mains and set to buzzing out the route between line at the m=ains LIVE input screw terminal, the relay contacts and the brown wire (live=) on the fan connector (WITH A dvm SET TO AUDIO BUZZER) revealed that the c=ontacts were now making too light a contact to work. A bit of adjustment wi=th a fine blade on the live fixed relay contact soon brought the clearances= back into kilter and I now have hot water again.I may have to replace that relay in future but I'll see how it goes.A word of warning - to gain access to the relays you have to take a second =protective cover off the pcb, the high voltage bit. There are plenty of ter=minals at mains voltage including the mains transformer terminals which are= very...

Aug 28, 2012 20 Replies

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Man at B&Q 14 years ago

Man

Bollocks to that.

MBQ

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Vaillant Turbomax 828 (628?) combi - fault found and fixed - for reference

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