Supply-Voltage Alarm; Faulty Pump Actuation; Checking The Sensor Board; Checking The Power Supply - Bosch ETT 008.31 Repair Instructions

8.13

Supply-voltage alarm

The exhaust-gas analyzer internally monitors the voltage at the filter capacitor C1 (nominal value 10V, see circuit diagram, Sections 12.1
and 12.2).
An error message is displayed when the voltage drops below a lower limit of approx. 7.6V or exceeds an upper limit of approx. 12.5 V.
This ensures that the exhaust-gas analyzer is unable to perform incorrect analysis when subject to under-voltage or overvoltage.
You can find out the current value of this voltage indirectly by means of a test function (see Section 4.2).
The displayed value is shown in % of the nominal value, whereby 7.6V = 70%, 10.8 = 100% and 12.5 = 115%.
In the case of exhaust-gas analyzers designed for a mains voltage of 220V, this means:
Lower alarm limit 170V = displayed value 70%
Nominal voltage 220V = displayed value 100%
Upper alarm limit 250V = displayed value 115%
Possible faults: - The mains voltage does not match the analyzer's nominal voltage. Check the nameplate, check that the
transformer is configured as shown in the circuit diagram in Sections 12.1 and 12.2.
- Faulty transformer, faulty rectifier V 1 or faulty capacitor C 1.
Replace faulty components.
8.14

Faulty pump actuation

The auxiliary power supply for the pump is obtained direct from the mains voltage. The voltage is dangerous contact
voltage. It is non-floating.
- Check with a multimeter at the pump terminals:
Pump switched on:
Pump switched off:
If these values are not met, check the "power electronics" module to ensure that the auxiliary supply is being correctly generated.
Proceed as described in Section 8.16. In the case of an electrical fault in the pump, replace the pump.
8.15 Checking sensor board

8.15.1 Checking the power supply

With the DMM, check:
Reference point Test point
X 81 (MD) X 82 (PSVD)
X 83 (MA) X 84 (PS V Uref)
X 85 (P 12 VA)
X 86 (N 12 VA)
X 87 (1W 9V) X88 (W 9V)
X 83 (MA) X54 (PSVZ)
8.15.2 Checking the "SELECT","ENTER o o o o o " and "TEST u u u u u " non-locking switches
If you suspect a fault, check whether the affected non-locking switch, the line to the motherboard or a function on the motherboard is
defective. Connect the DMM to X81 (reference point, MD).
Check at Measured value P5VD Press button Measured value
X64 + 5.2 V
X63 + 5.2 V
X62 + 5.2V
If the measured value does not equal +5.2V, replace the connecting line from X80 on sensor board to the X20 of the motherboard; if
the button is functioning incorrectly, replace the "sensor board" module.
46
U = 85 to 90V
AC
U = < 0.3V
AC
Measured value
+ 5.2V + 0.1V
+ 5.0V + 10mV
+ 12V + 1V
- 12V + 1V
AC 9V + 1V
+ 4.7 + 5%
SELECT
ENTER o
TEST u
0V
0V
0V