Vaillant VCW 2O Instructions For Installation And Servicing page 53

Repeat the following
cnecKS:
A. Earth Continuity.
C. Polarity.
D. Resistance to Earth
according to Instructtons
for British Gas
Multimeter.
Does Maan
Burner light?
Does
Pump run?
Difterentral
Valve
tested?
Are Pump
Setting
Terminals
tested?
240 V AC
lrom termrnal
5 t o l .
Replace faultY
DC Solenoid.
connectlons
on FFD
tested?
Move Heating Switch
ON-OFF-ON. Diaphragm
pin on Difterential
Valve has to move
OUT-lN-OUT. If not,
'1 .
Clean Venturi
2. Check Diaphragm
at differential valve
and replace, jf necessary.
Ref. to note 1 1 .
Check pump accordrng
to lnstructions tor
British Gas Multimeters,
Procedure 9.
)
.!
Note
Attention! Pull otf the NTC-plug for a short time only be-
cause the normal temperalure control is
out of function in that position. In this case the
appliance is only protected by the overheatcut-
off device.
8: For this purpose, open the control box as described in
Note 1. Unscrew the pilot gas tubes of the thermo-
electric casing and check it the black cables oJ the
micro switch are tight.
AfteMards install pilot gas tubes again
Before re-assembling the control box. check the fine-
wire tuse of the eleitronic. lf necessary. replace it'
Attach plugs A and B again and re-assemble control
box.
9: For this purpose, open control box as described in
-
f.fote f . Pull'off the multicontact plugs A and B The
electronic-printed circuit
can be
removed .by
unscrewind the cross-recessed head screw on the left
hand siddof the control box. Pull out the printed
iircuit towards the front and pull off the multicontact
plug as well as the white cable.
Install the electronic-printed circuit in reverse order'
Note 1 O: Attention: External llnes must not be connected to the
terminals l, ll and lll (short circuit!)
The black cable can be connected to terminal l, ll or I ll '
It must be checked whether the black cable is
connected tightlY enough
Note11: lf the movement of the diaphragm pin cannot be
checked optically. the pressure ditferential switch must
be removbd by unscrewing the 3 screws Do not
unscrew the two connection tubes!
Under perfect function the diaphragm pin cannot be
pushed back by hand, when pump oprates. lf lhis is,
however,
possible, the
venturi tube'
Pressure
difierential iwitch, connectionstubes or pump, must be
checked. Special attention must be given to the tact
that the venturi O-ring ist nol damaged.
R E