why does my car defroster not work

The car defroster is an essential safety feature, especially during those colder months. If you find yourself in the car with a frosted window and a defroster that isn t working, you'll need to address the problem immediately. Here are 12 common problems, or steps to go through, in order to troubleshoot the car defroster properly. 1. Buttons and Knobs
Sometimes a malfunctioning defroster is due to buttons or knobs for the heat or defroster that have become stuck. This can be solved easily by turning them back and forth until they stay in the position for the defroster. Sometimes you will realize that you were just off by one setting and the problem is solved. 2. Fuses A blown fuse could be another common problem when it comes to the car defroster. Testing with a voltmeter and replacing the broken fuse with an identical, working fuse can fix this problem quickly. 3. Missing Terminal Edges There is a chance that you are missing terminal edges on your window. If this happens to be the case, you can use a soldering gun to reattach them. 4. Battery The battery could be the problem if you find that other aspects of the car are not working in addition to the defroster. Jumping the car or replacing the battery can solve this problem. Likely your battery will only need a jump if this is an isolated issue, but if the problem persists and your car is relatively old, a battery replacement might be necessary. 5. Vent Issue There may be a clog in the vent that blows air onto the actual window. If this is the case, you can try moving the vent shield around and also vacuuming or dusting it. 6. Tinted Windows While this isn t a problem that you may think of, it is actually pretty common.


If you have tinted windows on your car and you find that the defroster isn t working, you may want to check to see if the tint has come off or cracked at all. If so, this may have caused some of the terminal edges to come off and you will need to and solder them back to get your defrost working again. 7. Anti-freeze Anti-freeze helps the car to run smoothly when it s cold. If you find that your defroster isn t working in the winter, adding anti-freeze is a good, easy solution to try. 8. Frayed Wires The wires connecting to the glass may be frayed or disconnected. To fix this, either replace the wires or use electrical tape to keep them from fraying any further. Be sure that there is no harm of a fire occurring. 9. Cracked Window While it seems obvious, a crack in the window would interfere with the defrosting of the car. While typically you can tell if the window is cracked, there can be times where it is small still and hasn t run yet. These cracks will obviously need a closer inspection to find. 10. Harness Connector This is located on the back of the driver s seat and tends to loosen at times. If this has happened, check to make sure everything is secure. 11. Damaged Grid A damaged grid may cause you to have a hard time with the defroster. Typically you will want a professional to help you fix this, but it can be done on your own. 12. Bad Electrical Connection A bad electrical connection can happen because of poor cleaning or buildup. Taking apart the wiring and cleaning with rubbing alcohol will ensure that the defroster works smoothly and that everything is safe and runs great. Front Defroster Buttons Stuck : In some cases a button or knob for the heating controls becomes stuck.


Moving them back and forth until it moves into the defroster position may solve this problem. Blocked fresh air intake : The fresh air intake is at the base of the windshield. It draws in fresh air, which helps the defroster function. If leaves or other debris are blocking the air intake it will affect the defroster. Vent Issues : If the vents on the dashboard are clogged, this will prevent the air from reaching the windshield. A quick vacuuming of the vents may fix the issue, if not the clog may be deeper in the system and require a professional. Low Anti-Freeze : The heater core depends on hot antifreeze moving through it to heat the inside of the car. If the vehicle is low on antifreeze, it can affect the heating and defrosting systems. Anti-freeze should be checked and replaced on a regular schedule. Malfunctioning Thermostat : The thermostat in a car works like a shut-off valve between the radiator and the engine. It remains closed when the car is first started to build up heat. Once the engine is warm the thermostat opens up to circulate anti-freeze to prevent the engine from overheating. If the thermostat is stuck open, the engine doesnБt warm up, so the defroster will not have the warm air it needs to function properly. Bad Heater Core : The heater core is basically a mini radiator that is located behind your dashboard. It is the heart of the heating system and essential to the defrosting system. There are a number of things that can cause a heating core to go bad, it can become clogged up due to contaminants in the anti-freeze, hoses can come loose or broken and control valves can become stuck.


A bad heater core will result in no heat, which means a non-functioning defroster. Bad Blower : The heating and defrosting system rely on an electric blower motor to move the hot air into the cabin of the car and through the defroster vents. If the blower motor is malfunctioning, the defroster will not work. Issues can range from a blown fuse to a bad blower speed controller. The blower motor itself can also go bad and need replacement. Rear Defroster Broken Grid : The most common issue with a rear defroster is physical damage to the heating grid running through the rear window. Damage can be caused by objects rubbing across the glass, which can break some of the grid wires. If the grid is damaged, it opens the circuit. The defroster will not function from the point of the break forward. Broken Tabs : There are tabs on the sides of the rear defroster, which connect the defroster to the window and the circuit. One of these tabs acts as the positive and the other is the ground. If one of these comes off or fails, the defroster will no longer work. Old Age : As defrosters age they can lose their conductivity which reduces their ability to conduct an electrical current. Repeated cleaning, the sun and objects rubbing over the grid will eventually wear the grid down and at some point may break it, rendering the defroster inoperable. Window Tinting Damaged Defroster Lines : When window tinting is applied it comes into contact with the defroster grid and can bond to the heating elements. It is possible that defroster lines can be broken during installation or removal of a window tint.

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