Mercedes-Benz seven cases of water failure

Fault 1
a W211 E240 sedan, users complained that the car ignition is turned off when the rain wading, water and interior of the vehicle.


After receiving the car, checked that, because the car left front drain plug, resulting in melting over no rain silk box, resulting in too much water into the car. Clogged drain at the thought, but maintenance personnel inspect the drain did not find too many leaves and debris. By pouring water tests and found that the left front drain hose (Figure 1) opening is too small, resulting in poor drainage, resulting in stagnant water can not be discharged after excessive rain, causing water inside the vehicle. In order to avoid recurrence of the problem here, maintenance personnel will drain hose left and right sides of the opening artificially expanded. Test by pouring water, drain the water smooth, can ensure that no excess water.
For the vehicle due to problems caused by water, I decided to disassemble relevant parts of the interior and carefully examined. Thus maintenance personnel to remove the relevant interior member, and placed outdoors for drying. When subsequently the vehicle line, the control unit and connectors, it was discovered connector portion and the control unit has been damaged, then it was replaced. Of water have been undamaged and harness connector, maintenance personnel drying with a hair dryer, and a double-check processing control unit harness connector and solder joints, solder spray drying and associated connectors at the rear the loose rust agent to oxidation.
For the associated mechanical elements, should be careful at the time of inspection. Maintenance personnel then checked the engine and related accessories. They were first engine cylinder intake and drainage, and artificial engine rotation, the engine may be rotated normally. For this reason, the maintenance personnel for the replacement of a new engine oil and filter. Then checks the generator, air conditioning compressor, power steering pump, air pump and the secondary tape follower wheels, engine parts, and found no abnormalities. Continue to check the automatic transmission, rear axle, we found a slight water phenomenon. Thus the use of the washing machine cycle of the automatic transmission of the automatic transmission oil completely replaced.

FIG. 2

After checking the completion of the loading vehicle-related complex, test driver side seat heating found failure. This car seat heating function from the seat control unit, but individually controlled by a control unit, the controlHarness system unit mounting box, the maintenance personnel is not found in the clean water vehicle. The maintenance personnel in the control unit from the wiring harness, the harness connector and found that the control unit (FIG. 2, FIG. 3) is corroded.

Figure 3

Fault 2
a Mercedes Benz car MB100, the user drives the vehicle accidentally slip into the river, vehicle maintenance at a special maintenance, five months after the vehicle maintenance, vehicle repair times due to a variety of failures. Later I got to the car service vehicle driving big noise, poor acceleration and moving flame failure.

Figure 4

by the maintenance personnel on the car inspection, determined that the engine noise is large, vehicle harness connector, relay has corrosion, which fuel pump relay (4) corrosion serious, it seems that it is the fuel pump relay failure led to the vehicle running for more than 1 h acceleration will appear unhealthy, moving flame phenomenon. According to test results, maintenance staff recommend that you check the engine dismantling, repair and replace the relay harness connector corrosion. The user does not agree to the dismantling of the engine, and then replace the fuel pump relay and repair the harness connector.
After the test, in addition to the engine operation noise is too large, the smooth exclude other failures.

fault 3
Mercedes-Benz W220 S600 sedan, the car users reflect the number of functional failure.
After receiving the vehicle, connected to the vehicle fault diagnostic detection, found SAM damage. Which causes damage to the air conditioning drain installation position error, resulting in vehicle air-conditioning water inlet, such that the SAM (the rear relay) water.
After solving air conditioning abnormal drainage problem, replace the SAM, and dry interior, keyless drive function test found invalid. Fault by performing fault diagnostic aid function, examination revealed system supply voltage of 4.7 V, the voltage should be the standard battery voltage. Now find the relevant circuit diagram, the power control unit and an antenna system with a pad of electrical supply. Based on past experience, combined with the specific fault of the car, I suspect the problem lies in this spot. Look carefully, it was found that the weld (FIG. 5) is wrapped wire harness, and the pressure in the SAMsurface. After ripping the wiring harness, open solder joints have been found severe corrosion.

Figure 5

After the weld repair, test troubleshooting.

Fault 4
a new Benz ML350 SUV, mileage is 760 km, the user reflect the warning light on the dashboard of the car Call the police.
After receiving the vehicle, the vehicle instrument connection failure detection, not found before the SAM detector. SAM found in the front side of the front passenger seat, and found a lot of water, soaked in water before the SAM. Carefully check the water stains, you can determine the water is very clean, not like the rain, maintenance personnel suspected of condensate as air conditioning. Found by dismantling, air conditioning drains right (FIG. 6) is not installed in place, the car air conditioner condensed water, resulting in water before SAM does not work.

Figure 6

After the water to clean and re-conditioning the right fixing drains, test troubleshooting.

Fault 5
Mercedes GL450 SUV, mileage of 1 400 km, the user is reflected in the car after passing a puddle, is often found to vehicle electronic fan rotation.
After receiving the car, checked that the water underneath the carpet. After preliminary examination, found no water site. After lifting the vehicle, the car has been observed not installed branched rubber car pier. If using compressed air branched car pier, the gas may enter the vehicle may be determined. Because the user found in time, but the master gateway control unit is damaged, the other control units is normal.
After the replacement of the main gateway (the CGW) control unit, and the placement of branched water cleaning vehicle interior plastic pieces, test troubleshooting.
by asking the user to know the car is purchased from a dealer, the dealer is not the Benz “4S” shop, so do not have a new car inspection.

failure 6
Mercedes-Benz W221 S350 sedan, users reflect the ESP warning.
After receiving the vehicle, the vehicle diagnostic connection failure detection, the system prompts the right rear wheel speed sensor signal distortion. On examination, found that the right rear wheel speed sensor connector corrosion, impactThe signal output of the sensor. Check left wheel speed sensor connector, there is a slight corrosion phenomena. Therefore, the plug is not easily found below the rear seat, so maintenance staff did not rule out the water here.
After the damaged line maintenance, troubleshooting test.

fault 7
Mercedes-Benz W221 S350 sedan, after users complained that the car air-conditioning failure.
After receiving the vehicle, the vehicle diagnostic connection failure detection, the control device prompts the air conditioning unit fails. So maintenance personnel to control the air conditioning unit, it was discovered control unit because of water corroded. So here is the water from where it? Carefully check the water sites and found only a trace of water stains the carpet, seats at the obvious traces of water. Later vehicle inspection maintenance personnel with a washout, but no water site. After careful asking the user to know the car has once rainy night did not shutting windows, skylights water from entering. The user reflect the situation, the maintenance personnel with the vehicle sunroof open some washout car, found that the water stream just after the air conditioner control unit and no traces of water on the ceiling. After
After determining the cause of the malfunction, the maintenance personnel to replace and repair the air conditioner control unit harness connector, then test troubleshooting.
Summary: We usually have encountered a fault in the vehicle’s water maintenance, water failures are generally divided into external and internal influent water, mostly rainwater or external water washing water, water is mostly internal antifreeze heater and air conditioning condensate water radiator. And the cause of the failure are varied, including when the vehicle is too deep wading wading, poor drainage holes and drainage, poor sealing of the sealing element and associated number of man. When the fault repair these vehicles, you must find the cause of the water. Causing the vehicle when the vehicle is unable to run normally after the water or wading, maintenance personnel should be checked to determine the cause of the water vehicle, in order to avoid the water situation again; when checking the vehicle wiring harness connector plug and control unit, should be a comprehensive inspection can not be missed, all inspection, maintenance and repair than to save time; check the engine stalled after the failure of the water, to strictly observe the maintenance program, which is to drain, and then manually turn the crank, to determine the engine has not been hurt before you can start the engine again; checking the engine follower member, the first manual inspection, inspection after restarting the engine, to avoid damage in succession; number of hidden faults refitted after the vehicle, to a multi-test, multi-pass and all the features of the vehicle to check.
In short, the water vehicle troubleshooting, to be more careful, can not only repair the surface, but to in-depth checks and maintenance, to leave precautionary measures lead to other failures.

(Hou Zhenfang)

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