Vaillant ecoMAX 646 Service Manual download pdf (Page 49)

49

Sheet E Check fan/flue gas system

Does yellow fan operation indicator ( ) glow?

Does yellow ignition

indicator ( ) glow?

Defective switch

board.

Does burner

light?

Go to Sheet H

Go to Sheet F

Check air/flue gas system is correctly

fitted and not obstructed. Check Pitot

tube ( in fan outlet) and air hoses are not

obstructed and are correctly aligned.

Check or replace air pressure switch.

Does fan run?

Is 230 V~present

across fan terminals?

Does yellow Central heating

demand indicator ( ) glow?

Check/replace fan

No heat demand, go to sheet C

Switch main on/off control off and

on again. Does fan now operate?

Check NTC. Disconnect NTC

lead at plug (3, fig. 37), does

fan now run?

Yes

No

No

No

Yes

Yes

Yes

Check connection to

NTC temperature

sensor clean and

tight. If o.k, replace

NTC sensor

No

Replace

main

switchboard

No

No

No

No

Yes

Yes

Yes

Yes

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