Vaillant ecoTEC sustain 24 Installation And Maintenance Instructions Manual page 26

9 Troubleshooting
9.7.2 Replacing the fan or gas valve
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1. Remove the air intake pipe.
2. Remove the plug from the gas valve (7).
3. Remove the plugs (6) and (9) from the fan motor by
pushing in the latching lug.
4. Unscrew the connection from the gas valve (8).
5. Unscrew the three screws (2)-(4) between the mixture
pipe (1) and the fan flange.
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6. Remove the entire fan/gas valve unit from the product.
7. Unscrew both fixing screws (1) on the gas valve and
remove the fan from the gas valve.
8. Replace the defective fan or the defective gas valve.
9. Install the gas valve and the fan in the same position as
before. Use new seals for this.
10. Screw the fan to the gas valve.
11. If you had removed the gas pipe, screw the cap nut
of the gas pipe (2) only loosely to the gas valve. Only
tighten the cap nut on the gas valve after the installa-
tion work has been completed.
12. Refit the entire fan/gas valve unit in reverse order. You
must use a new seal (5) for this.
13. Ensure that the order in which the three screws are
screwed in between the fan and the mixture pipe cor-
responds to the numbering (3), (2) and (4).
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14. Tighten the cap nut (2) on the gas valve and the cap
nut (8) between the gas pipes. In the process, secure
the gas pipe against twisting. Use new seals for this.
15. After you have completed this work, carry out a leak-
tightness test (function check). (→ Page 22)
16. If you have installed a new gas valve, adjust the gas
ratio setting. (→ Page 18)
9.7.3 Replacing the heat exchanger
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1. Drain the product. (→ Page 30)
2. Detach the condensate drain hose from the heat ex-
changer.
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3. Remove the clamps (2) and (3) from the area of the
flow and return connection.
4. Disconnect the flow connection.
5. Disconnect the return connection.
6. Remove both screws (1) from both brackets.
7. Remove the lower three screws (2) on the rear section
of the retainer.
8. Move the bracket round to the opposite side and attach
the upper screw (1) to the side.
9. Pull the heat exchanger downwards and to the right,
and remove it from the product.
10. Install the new heat exchanger in reverse order.
11. Replace the seals.
Installation and maintenance instructions ecoTEC sustain 0020253094_01
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Note
Instead of grease, use only water or com-
mercially available soft soap to aid installa-
tion.