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Viessmann wb2 8-32 blower problem

tim smith
tim smith Member Posts: 2,772
Hey guys, got a customers boiler going into 06 error code.  2009 vintage. Have 24 v to fan motor but intermittent failure to start fan. Not Seized or overloading.  I suspect a bad fan circuit board ie bad fan.  None in town.  Ran through trouble shooting guide but no reference to testing pwm signal on comm cable at fan. Any input?
 Thanks in advance.


  • GGross
    GGross Member Posts: 1,075
    Well unfortunately it could be the fan or the differential pressure sensor. IF you have one available locally, the sensor is about 1/6 the cost of a new fan
    7822897 sensor
    7831026 fan

    If you are having trouble getting these from Viessmann I have them available in Michigan, the fan is not cheap mind you, about 1/4 the cost of a new boiler, and unfortunately I have seen that particular models fan fail after 15 years or so, it is not uncommon. The sensor is a slightly more common failure though. These were susceptible to damage from power fluctuations and really need a power conditioner connected to them if you don't have one already
  • tim smith
    tim smith Member Posts: 2,772
    It was the fan, I got one flown in from Ferguson. it could have been com cable, main board etc but was 95% sure on blower. Running, whew. Really wish they had some published com volt readings, knowing its pwm signal. Could have at least ruled out board and cable.
  • Jamie Hall
    Jamie Hall Member Posts: 23,554
    You really need a scope, not a voltage reading, to trouble shoot PWM problems.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England