Troubleshooting: Automobile Exhaust Gas Analyzer & Opacimeter




Turn on the power switch. The instrument does not work, and the LCD screen does not display anything.



● The power supply cable has not been fully connected.

● To fully connect the power supply cable.

● Fuse blown.

● Replace the fuse.

●Display damaged.

● Contact us to repair the display.

HC residual is out of tolerance, i.e. HC value is higher during pumping ambient air after zero set.


● Ambient air is polluted.

● Place the sampling probe in clean air.

● Excessively higher content of HC residual of vehicle exhaust and excessive measuring time, which lead to the deposition and adsorption of HC in the path and components of the sampling system.

● Put the sampling probe in clean air and perform real-time measurement for a while (about 10min). Clean up HC residuals inside the tube with clean air. If it doesn’t work, remove sampling probe and tube, and clean with compressed air.

● Replace pre-filter and water filter.

● Contact us to replace the internal path.

Leak check fails







● Gas leakage at the connection between the cup and base of the water filter.

● Check if the seal ring is still in place or effective. Check if they are fully connected. Replace seal ring or screw tightly the connection.

● Sampling probe inlet not plugged tightly.

● Plug the inlet of sampling probe tightly.

● Leakage at the connection of sampling probe.

● Connect and tighten the parts again.

● Aging of the ends of the sampling tube or short conduit results in poor sealing.

● Cut off the aging part or replace with new sampling tube.

● Sampling tube cracked or pierced.

● Replace with new sampling tube.

● One-way value leakage.

● Replace with new one-way value.

● Air bag of the pump is damaged.

● Replace with new air bag.

Measured values for HC, CO, CO2, NO, and NO2 are zero or extremely low.




● No sampling probe inserted into the exhaust pipe of vehicle.

● Insert the sampling probe into the exhaust pipe of vehicle.

● Sampling pump is damaged.

● Replace air bag or sampling pump.

● Pipes inside the instrument are loose.

● Connect the pipeline again.

● Optical bench is damaged.

● Contact us to repair the optical bench.

“Flow” is blinking on the lower right during real-time measurement.

● The sampling system of the instrument is blocked by dust, oil sludge and other dirt from the vehicle exhaust, resulting in the significant decrease of flow rate.

● Replace pre-filter.

● Replace water filter.

O2 channel shows abnormally high or unusual readings when measuring vehicle exhaust gases.

● O2 sensor aging for use of more than a year.

● Replace the O2 sensor.

During measurement, the CO2 concentration fails to reach 6%.




● Insufficient pumping air or pump system damaged.

● Replace the pump or diaphragm.

● Leakage check fails.

● Check leakage and repair, and then perform leakage check again.

● Water filter is draining or electrode rod circuit is open.

● Replace the O2 sensor. Clean the water filter and keep the electrode plate dry.

● Sampling probe was not inserted into the exhaust pipe.

● Insert the sampling probe into the exhaust pipe for a depth of 400mm.

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Nanhua Instruments Co., Ltd.

Add: 1 Kehong, Rd., Guicheng, Nanhai District, Foshan City, Guangdong 528251 CHINA
Tel: +86 757 86718778
Export Dept.
Tel: +86 757 86718629
Email: Export@nanhua.com

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