Saunier Duval 624

[ScottishGasMan]

Hey all, had a fault recently with a sauner duval 624, (or maybe 623 lol) combi.

On creating a hw or heating demand, the boiler doesnt do anyhting.

teh fan is getting 90 volts at all times as it should ad the pump is off. When demand is made, the fan still only gts 90 volts and the pump tehn gets about 150v. does not fire up dosn not go any further.

Spoke to the manufacturers for ages on it, they saif if its not giving the fan full voltage then its the PCB, (which was changed the day before lol) yet its teh same relay that supplys the fan full + pump so he didnt understand what else it could be.

tryed shorting out the thermistors, making and breaking APS connections etc, all 3 microswitches working per manufacturers checks.


I need help, ive never had a boiler that doesnt work that Ive not been able to tell whats wrong, its not like its an intermittent fault.

 

[Gasguru]

Some models are fitted with a water pressure switch on the left. Are all the microswitch contacts (NO and NC) less than an ohm?

 

[ScottishGasMan]

no water pressure switch on this one on the left, all switches <1ohm when closed, cant remember what was open and closed but went through it twice wit the manufacturers and they said the micro switches were fine!!