A functioning windshield washer always ensures a clear view when driving. If no fluid comes out of the nozzles when you switch on the washer on your Mercedes-Benz C300, it can have various causes. What these are and what you can do about it, we explain in this article.
The most common causes that hinders normal operation of windshield washer system on your Mercedes-Benz C300 are clogged spray nozzles, leaking hose, blown fuse, pump failure, frozen fluid or any fault in the electrical system.
1. Clogged spray nozzles
Clogged nozzles are often the reason why the windscreen washer system does not work on C300. They are located near the bottom of the windshield, where dead insects, dust, pollen and limescale are often deposited. The impurities can then be collected by the rainwater running off, which then gets caught in the nozzles and gradually clogs them.
In older vehicles, drivers could easily clean the nozzles themselves by inserting a fine needle into the holes without any effort. However, modern cars are equipped with so-called “fan nozzles” or “micro-emitters” which produce a wider and finer spray jet. With each pumping process, a larger area is wetted with washer fluid, at the same time, however, the finer nozzles tend to clog faster.
Diagnosis: Before you decide on replacing the nozzles, you must rule out any problem with the washer pump or the hoses. The easiest way to check if the pump is working is by doing a noise test. Park your C300 in a quiet place. Switch on the vehicle and turn down the driver’s door window. Now, stand outside and switch on the windshield washer. You should hear the whirring of the pump. If there is no sound, then it means the pump has failed or there is no power to the pump. If you do hear the whirring sound coming from the front of your C300, the pump is working and the culprit is most probably clogged nozzles.
Important: Before replacing the nozzles, make sure the fluid is being pumped normally. Pull the end of the hose out of a windshield washer nozzle on your C300, and then turn on the washer system. You should see the fluid gushing out of the hose.
If there is little or no flow of fluid from the disconnected hose, it means the nozzles are probably good but the problem lies somewhere else.
2. Blown fuse for washer pump
The pump of the windscreen washer system on Mercedes-Benz C300 needs electricity to work. In case of a faulty fuse, the circuit is interrupted and the pump can not work.
Check your C300’s owners manual or the fuse box cover to find the exact location of the fuse for the washer pump. If the fuse is blown, replace it with a new one with the specified amp rating.
To check the fuse, pull it out of C300’s fuse box using a fuse puller or needle nose plier and hold it against the light. If the metal strip is broken in the middle, the fuse has blown. You must replace it with one of the same amperage and therefore the same color. It does not matter in which direction you insert the fuse.
3. Pump failure
The electric pump that feeds fluid to the windshield washer nozzles could have failed in your Mercedes-Benz C300.
You can do a quick diagnosis by performing a noise test.
- Park your C300 in a quiet place.
- Turn on your vehicle and open the driver’s door or roll down the window.
- While standing outside your C300, switch on the windshield washer.
- You should hear the whirring of the pump. If there is no sound, then it means the pump is not working in your C300.
No power to pump
If you do not hear whirring sound of the pump when you turn on the windshield washer system on your Mercedes-Benz C300, you should first check the fuse for the pump. If the fuse is not blown, check if the pump is getting any power. This can be done by removing the electrical connector from the pump and connecting it to a multimeter. The multimeter should read around 12 volts when you switch on the windshield washer, which indicates that the pump has failed in your C300 and needs to be replaced. If the multimeter reads very low or zero volts, it indicates a fault in the wiring or electrical connection – all electrical connectors and wires that feed power to the pump should be inspected for damage.
4. Leaking hose
If the pump is working, but windscreen washer still does not work, Mercedes-Benz C300 owners should check the hoses. If they are cracked, loose or leaking, they must be replaced. An exchange is also recommended if the elasticity of the rubber hose at the connection point to the nozzle decreases. However, the hoses can also have easily fallen off due to vibrations in the engine compartment.
Rodent Damage: If bite marks or the like are discovered, there is a high probability that a rodent has let off steam in the engine compartment of your C300. Then it is important to carefully examine all other cables and hoses for damage, including electric wires for the windshield washer pump.
Diagnosis: You don’t have to disassemble the engine compartment to check for a leaking hose in your C300. Park your vehicle on a dry pavement and turn on the windshield washer for a few seconds. Now look under the front of your vehicle, if you see a puddle forming then there is a leak, otherwise problem lies somewhere else.
Note: Keep the air-conditioning off in your vehicle when diagnosing a leaking hose, as condensation from the evaporator coil is also drained under the vehicle.
5. Blocked hose
In rare cases, a dirty or pinched hose can be responsible for windscreen washer system malfunction on Mercedes-Benz C300. To diagnose, first open the hood and pull the end of the hose out of a windshield washer nozzle, and then turn on the washer system. You should see the fluid gushing out of the hose. If there is little or no flow, and the pump is working, then there is probably a blockage in the hose somewhere. Inspect entire hose and clear any blockage.
Note: If you see washer fluid gushing out of the detached hose when you switch on the windshield washer in your C300, but the fluid doesn’t flow when the nozzle is connected, it means the nozzles are clogged.
6. Frozen washer fluid
In winter, frozen washer fluid can also prevent the windscreen washer system from working in Mercedes-Benz C300. Most of the time, C300 owners have forgotten to fill in a mixture suitable for winter. If this is the case, all that will help is a warm garage or a long drive to thaw the fluid again. The windshield washer reservoir in C300 should also be thoroughly examined for cracks and holes. Because: water expands by around ten percent when it freezes, which can lead to a well-filled container bursting.
7. Faulty switch
You turn on the switch that activates the windshield washer system on your Mercedes-Benz C300, but nothing happens, the pump is not working and you don’t see any volts on multimeter at the pump’s electrical connector. In rare cases, this could happen due to faulty switch. Diagnosing this problem requires removal of the switch from C300’s interior and then tested with a multimeter.
8. Empty reservoir
It may sound kind of obvious, but have you checked if there is sufficient fluid in your C300’s washer fluid reservoir? You may have just forgotten to refill, or if you have refilled the reservoir recently, it may have been drained out due to a leak in the reservoir or the hose. Double check if there is enough fluid.
There are many reasons why windshield washer may not be working properly on your Mercedes-Benz C300. When looking for the reason, you should always start with the most obvious cause, clogged washer spray nozzles.
In any case, it is advisable for laypersons to visit a workshop. In the event of a defect, the mechanic can directly initiate the repair.