Set your voltmeter for the 20-volt scale, and attach a couple of postage-stamp-size pieces of aluminum foil to the leads. While driving 35 mph with the rear defroster activated, the rear windshield shattered without warning or an impact. Oct 12 2016, 1:21am. Imagine accidentally leaving it on during a long trip on a summer day. Sometimes a break in the painted circuit or another problem can be spotted with a visual inspection. Clean the area of the break with alcohol and a fresh, untinted paper towel. First Time I've used the rear window defrost. The smallest break or crack in the grid can cause the defroster to fail so careful visual inspection is needed. I am having the same problem where my Heated Mirrors both work but not the rear defrost. 2003 Jetta GL TDI. Somewhere in the circuit there will be a relay to switch the high current necessary for the grid’s operation. Remember, the timer will turn off the current within 5 to 10 minutes, so you’ll need to keep track of the timer’s time window or you’ll be looking for current that’s not supposed to be there. Its test lamp will illuminate with the slightest bit of power running through it, which is useful in troubleshooting the defroster lines. If part of the lines work for the defroster, there is a issue with in that grid so they do have repair kits to connect the break in that grid, so the only way to isolate that issue is with a ohm meter. The element is imprinted onto the glass and some of your conductors must be cracked. You can either jump 12 volts to the relay’s coil to make it pull in, or bypass the relay with a large-gauge jumper to see if the grid’s wiring is intact between the relay and the window. If it’s wintertime, you’ll need to work in a heated garage, and have the vehicle inside long enough for it to warm up to at least 65˚ F. Again, clean the area with alcohol. ! On trucks with the electric rear window, pressing the right hand knob turns on the heated exterior rear mirrors. It was snowing lightly and I briefly turned on the rear window defroster to melt the snow. This will prevent the probes from scratching the grid. Rear Defroster. Clean the surfaces with alcohol and use 60-40 rosin-core solder. Next, touch the other test lamp wire to the tab on the other side of the circuit (don't disconnect the wire on this one). Couple that with the extra demands on the battery for starting in cold weather, and there may simply not be enough alternator capacity to keep the battery charged adequately. Your back window likely has lines through it, those lines are part of an electrical system. You have two repair options here: soldering and gluing. If it lights up, the grid is getting power. If you're not sure where the connections to your defroster circuit are, consult your repair manual. Grid attached to the glass everywhere, but simply no defrosting action at all? Age: 38 Posts: 1,110 Likes Received: 779 Joined: Oct 13, 2017 Location: South Idaho. Does your AC work? It works, just doens't put much heat on the window to remove the frost I had this am. Paint a stripe of the kit’s conductive paint across the break. Mustang Forums. 14 minutes ago #1 I'm having an issue with my rear defroster, it doesn't work. Check your connections. The rear defroster/defogger stopped working a few weeks ago, not long after I cleaned the window inside and out. This project was originally published in the January 2001 issue of Popular Mechanics. Old wiring or a blown fuse can cause a disconnect. Attempting this repair in the middle of winter in your driveway will not get you the desired results. If the switch is bad, you’ll be able to jumper the switch and get 12 volts beyond there for diagnosis. Many auto departments in large stores, and almost any dedicated auto parts store, can sell you a repair kit. If the fuse doesn’t look blown, check with your voltmeter—with the key on and the defroster on, you should see 12 volts at both fuse terminals. If you have the electric sliding rear window, you can't have the defroster. The resistance wires are silk-screened, essentially painted, onto the glass. Good question on rear window defroster repair. Start by measuring the voltage across the entire length of the grid. The contact owns a 2014 Ford F-150. If it doesn't, check for a bad fuse and replace it if necessary. Most modern cars use a timer circuit to turn the grid off after a reasonable length of time. But you may need to replace the timer—which may be integrated into a larger box of electrical controls buried under the dash. Try these repairs yourself, and save money and be safe this winter! The idea of running electric current through a circuit to generate heat and clear up your car's rear window arose a few decades after automobiles took to the roads. Here are 12 common problems, or steps to go through, in order to troubleshoot the car defroster properly. Check your owner’s manual for the location of the rear defroster fuse. If you have several grid lines that are damaged, simply repeat the process. If the dangling wire has a connector on the end, chances are it has worked its way loose from the painted grid. I haven't had a chance to inspect each line for damage but at a quick glance they looked all good. Make sure the rear defroster switch and the ignition key are turned on. The lines on the rear window are electrical. Disconnect both wires from either side of the defroster grid and touch one end of your tester to each wire. If you must clean the rear glass, scrub gently, and in the direction of the grid, not across it. 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