Problem solving

8Problem solving

8.1Error code diagnostics

To remove error code from the

idisplay, press the reset button.

Display

Cause

 

Solution

 

Fault in the flue gas limiter.

1.

Check continuity of the flue gas limiter (see Fig. 64, page 49).

 

 

 

Go to steps two and three to determine air box temperature

 

 

 

sensor fault and replace it.

 

 

 

2. Check for flue gas leakage around the top and bottom seals of

 

 

 

heat exchanger as well as the viewing window.

 

 

 

3.

Check that venting is within specifications (see Section 3.3).

 

 

 

Long vent lengths, venting with more than three elbows, blocked

 

 

 

vent or combination venting may cause this failure.

 

 

 

4.

Check that flue gas limiter connector and spade connections

 

 

 

are secure.

 

 

 

5. Unplug heater and check the two main plug connections inside

 

 

 

the control board.

 

Appliance selection on “P7” mode

1.

Check “P7” mode: water heater requires setting “NC”.

 

is not correct.

 

2.

Check jumper and connection on sensor at upper right hand

 

 

 

corner of heat exchanger.

 

 

 

3.

Measure jumper resistance, must be 115-125 ohms.

 

Backflow temperature sensor

1. Check backflow temperature sensor connection and resistance.

 

defect - happens if sensor is

See Fig. 62, page 47 and Fig. 64, page 49.

 

disconnected or short circuit.

2.

Replace backflow temperature sensor.

 

Outlet temperature

sensor fault

1.

Check red wire connections at hot water temperature sensor.

 

(Temperature below

freezing or

Clean terminals with an eraser. If badly corroded, replace sensor

 

above 210°F).

 

and wire harness. See Fig. 64, page 49.

 

 

 

2.

Sensor may trip if water temperature drops below freezing to

 

 

 

protect heater from freezing conditions. Any damage due to

 

 

 

freezing conditions is not covered under warranty.

 

 

 

3.

Clean inlet filter screen and clear any debris out of shower

 

 

 

heads, faucet aerators and whole house filters.

 

 

 

4.

In areas where water has a high mineral content, periodic

 

 

 

descaling may be necessary.

Table 20

 

 

 

 

* By installer or service technician only.

 

 

6 720 608 542

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Bosch Appliances GWH 2700 ES NG, GWH 2700 ES LP, ESVVT manual Problem solving, Error code diagnostics