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How to fix rear window defroster on jeep wrangler?

The rear window defroster in a jeep wrangler is electrically operated like in most modern vehicles. The rear window has thin lines running across it which are electrical fibers embedded in the glass that heat up once the defroster is activated and they get their power from the wrangler’s electrical system. Here, we’re going to see How to fix rear window defroster on jeep wrangler?

The defroster switch in a jeep wrangler is mounted in the instrument panel left of the steering wheel for the wrangler XJ and right of the steering column for the wrangler YJ and for the JK and JL it is located at the bottom right side of the blower control knob.

The rear window defroster rarely gets damaged and the following are some of the reasons that can lead to the malfunctioning of the rear window defroster. 

Things you can do to avoid defroster strands from Breaking 

Defroster stands are the thin electrical fibers running across the glass. They are reasonably tough and do not get damaged easily. They mostly get damaged physically and the following are some ways to protect the defroster strands from being damaged 

  • Do not let cargo rub against the glass as friction between the glass and the cargo may damage the thin electrical fibers. 
  • Use a clean and soft rag to clean your wrangler rear windows. Do not use a rough rag or a brush no matter the amount of dirt on the windows. Just loosen the dirt with water and wipe the dirt off with a clean and soft rag 
  • When you apply tint on your wrangler’s window paned it comes in direct contact with the defroster grid lines and when you decide to remove the tint separates the small heating particles on the defroster strands as they stick to the window tints.
  • This causes an increase in resistance and which leads to defroster failure. Defroster grid lines can also be cut during installation but this is a quick fix if you know how to use the defroster repair kit.  

There are other reasons why defrosters fail such as: 

Damaged Defroster Connectors – These are located on the sides of the window panes, on one side the connector is positive and on the other side the tab is ground, if a connector comes off this will lead to the total malfunctioning of the defroster grid in that specific window.

Aging of Defrosters – Some old defrosters begin to lose conductivity and become highly resistive which limits the ability to conduct electrical current and heat up. Over years of use scorching by the sun, cleaning and scratching of the silver coating covering the grid lines come off thus creating more electrical resistance until the defroster grid eventually stops working. It is recommended you fix the small breaks in the defroster strands once you notice them or else you will incur more cost in replacing the whole grid or buying a new window pane. 

fix rear window defroster on jeep wrangler

Damaged defroster grids are costly to fix but you can do this yourself at much lower costs. If you decide to do it yourself then you’ll need to get a rear window defroster you can from a local automotive parts store or online.

There are two most commonly used and recommended rear window defroster kits, the Permatex complete rear window defroster repair kit and the Eastup Rear Window Defogger Defroster Grid Line repair kit.  

If your rear defroster is not working there are a couple of issues that can lead to this apart from the defroster strands getting damaged. There might be an issue with your wrangler’s electrical system (mostly the fuse to the defroster switch).

When there is an issue with your wrangler’s electrical system the defroster grid does not receive any power therefore it does not function. If the fuse is blown then there must be an issue that leads to it and if you do not perform a maintenance check on your wrangler’s electrical system then you will end up replacing fuses now and then.  

The electrical system that powers the defroster strands consist of the following 

  • The battery which is the power source.
  • Electrical wiring from the battery to the fuse block. 
  • Wiring to the defroster switch. 
  • Wiring from the switch to the defroster connectors.
  • Connectors on the defrosters.
  • The whole defrosting grid consists of thin strands of electrical wires with heating properties.

Replacing the fuse is usually a short term if there is any damage, whether serious or slight you will end up replacing more if you don’t replace the damaged component.

If you can diagnose and fix problems with your electrical system powering the defroster strands, do so, and if you can’t take your wrangler to a specialist who can handle that for you.  

fix rear window defroster on jeep wrangler

The defroster switch itself might be faulty meaning that the rear defroster cannot be operated. The following is a guide to check the functionality of your rear window defroster switch. 

  • Locate the rear window defroster switch and check the switch for any exterior physical damage 
  • Turn the ignition and switch on the rear window defroster switch 
  • Take multiple readings of the glass between intervals to verify whether the defroster is heating up. At this point, you should also check for a blown fuse, if it’s blown, replace it and recheck glass temperatures.
  • You should also check for broken defroster lines. If there are neither broken defroster lines and your wrangler’s electrical system has no issues then there is an issue with your rear defroster switch. 

How do you fix rear window defroster switch on jeep wrangler? 

  • The first thing you should do is to turn your wrangler off.
  • Install a nine-volt battery on your cigarette lighter to keep your onboard computer on. 
  • Open the hood of your wrangler and disconnect your battery taking the ground cable off the negative terminal thus disabling power to the vehicle.
  • Locate and remove the screws that hold the dash panel in place and remove the dash panel after removing all screws. 
  • Remove the screws that secure the rear defroster switch to the dashboard.
  • Disconnect the wiring harness from the switch and clean the terminals on the wiring harness using an electrical cleaner. This strengthens the connection between the switch and the wiring harness. 
  • You can test whether the switch is working by reconnecting the battery terminals and turning it on then measure the rear window temperature.
  • If there is an increase in temperature between intervals then the switch is functional but if there is no change in temperature you need to replace the old switch with a new one. 
  • After ensuring that the switch is functional re-screw everything back into place. 

How to fix broken defroster strands on jeep wrangler?

  • Turn on the defroster switch and monitor the change in temperature of the rear window.
  • Inspecting the grid to find the broken defroster line(s). 
  • Run a voltmeter slowly through each defroster line monitoring the voltage. Wherever there is low voltage reading, there is a break in that line.
  • You can mark that point with masking tape just to ensure that you do not inspect it over and over again. 
  • Switch off the defroster before starting to work in the broken lines for safety purposes.
  • Using a glass cleaner, clean the area(s). spray a little glass cleaner and use a clean soft rag to wipe the area you intend to repair. By cleaning you remove all impurities such as dust and rust which may cause inefficiency and also cleaning enhances proper adhesion of the conductive defroster paste you will be applying. 
  • Once the area is clean and dry stick masking tape on the sides of the broken part of the grid line. 
  • After the masking tape has been stuck correctly apply the conductive paste between the masking tape strips. Apply the defroster paste slowly and carefully to ensure the entire break is covered. Leave the paste to dry for a while depending on the temperature of your location. Once you notice the paste is soft and shiny, it is dry.  
  • Take off the masking tape strips slowly and carefully.
  • Turn your wrangler’s ignition key to the “on” position and turn on your rear defroster switch.
  • Measure the temperature of the defrosting grid at different points especially at the point(s) that you have repaired and areas close to the point(s) that you have repaired.
  • Do this in intervals, if there is a steady and uniform rise in temperature of the glass then your wrangler’s rear defroster grid is fully functional.
  • If you don’t have access to a thermometer or any other measuring equipment you can try pouring ice-cold water on your rear window then turn on the switch, If you notice tiny droplets dripping down the window then the defroster grid is working. 

Conclusion 

Repairing the rear window defroster all by yourself can be a little bit tricky especially in cleaning the damaged line(s) and applying the conductive paste. All in all, repairing broken defroster grids or other components in the defroster grid circuit saves you a lot of cash since some technicians overcharge and it’s not that hard and does not take up much time and costs.

Driving with a damaged defroster grid especially in cold weather conditions is not advisable unless your wrangler has a backup camera you won’t have a rearview as the rear window will be foggy and you can’t keep on wiping it since the fog will recollect after a short while.