ECHOMAX 835E problem, S54-F23, HELP PSE !

[GiAl]

I have a problem with an Echomax 835E: after HW running for about ten minutes, the water gets cold and the boiler goes in S54 state.
A couple of days ago, the house got freezing cold and the display was showing F23.
When the thermostat clicks on, the boiler flame goes to max for 10secs or so, then goes down. I believe that earlier it used to stay high until for a while and then it started to modulate until the set temp was reached.
A technician came this morning, called Vaillant to enquire about the code (!) and then, upon their advice, disconnected from the PCB the 2-wire connector coming from the pump, which then started running at a higher speed. The guy said that if the fault occurs again, the pump must be replaced. After 10min the boiler went in F23.
I am concerned by the troubleshooting style of this official Vaillant technician and would highly appreciate the advice of any of the experienced members of this forum !
The pump I have is a Vaillant 160967 Grundfos VP5ZE PWM S2, which I am told is has a part nr. 160959. I am puzzled by the 160967 on it and the 160959 that Vaillant told me. Is it the correct part nr ?
Thank you !

 

[SShar]

Hi GIAI,

F23 code usually is an indication of poor flow and so the problem could be with the pump or main heat exchanger. It's more than likely to be the heat exchanger but you'll need to check for pump resistance -which should be 150 – 200 ohms.

hth

 

[Agile]

I dont see how a Vaillant technician would need to call the manufacturers!

He does not seem to have much of a clue from what you say.

It seems that he disabled a multi speed pump!

Tony