Bosch ETT 008.31 - Checking Fault Monitoring; Performing the Leak Test

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- Fluctuations (noise) may be caused by dirt in the analyzer part, a defective receiving chamber, a faulty (noisy) channel amplifier or
an unstable reference voltage 5 V
Ref
.
Dirt in the gas-conveyance system primarily affects the HC measuring channel. Whenever errors caused by dirt arise, cross sensitivity
to condensation also increases.
Therefore, if fluctuations (noise) occur in this channel, first check the cross sensitivity as described in Section 6.4. If the specified limit
values are complied with, then check:
Fluctuations in one measuring channel may stem from a fault in a receiving chamber. Therefore, check the bridge working point,
bridge diagonal voltage and U
Ref
of the affected channel amplifier as described in Section 8.7.
If fluctuations are present in all measuring channels, check U
Ref
to Section 8.7.
- If the HC display has not yet reached a value < 20 ppm after 2 minutes, again, dirt is likely to be the culprit. In this case, remove the
exhaust-sample intake hose from the test-gas inlet. If the displayed value then drops appreciably, thoroughly clean or replace the intake
hose.
If the displayed value still deviates excessively after the intake hose has been removed, clean the analyzer part to Section 10.4. During
this process, clean all parts which convey test gas, and replace the hoses if necessary.
5.6 Checking fault monitoring
- Block off the zero-gas inlet on the rear of the device with your finger.
- Press the pump button.
- During system adjustment, the error message
Err 1Err 1
Err 1Err 1
Err 1 must appear in the CO
2
display field (flow interrupted during zero adjustment).
Release the zero-gas inlet, block off the test-gas inlet (bend the hose).
- Press the pump button.
After system adjustment, the error message
Err 2Err 2
Err 2Err 2
Err 2 must appear in the CO
2
display field (test-gas flow interrupted). If these error
messages do not appear, a fault in the flow monitor is possible. Perform trouble-shooting as appropriate in accordance with Sections
8.1 and 8.2.
5.7 Performing the leak test
(see Section 3.1.1)
At the half-yearly test, the use of test-gas with 10 to 15 % vol. CO
2
(test gas no. 1) is compulsory for performing this leak test. Introduce
the flow to the device via the calibration-gas inlet (set admission pressure to 0.7 bar on bottle-pressure reducer). Fit seals, as indicated
by ”
AbdAbd
AbdAbd
Abd”, on the test-gas hose between the test-gas probe and coarse filter GF 1.