For the second time in the last 24 months my rear defroster doesnt seem to be working. The first time I took it in to the dealer and under warranty, they had to replace the entire rear window. The side view mirror defrosters still worked and they still work now. It just seems that the rear isnt working again and this time my warranty has run out.

Should I take it back to the dealer and hope they honor their work? My 3yr/36k expired 4 months ago. How could I even test that it is working? Ive only had to use it 2 or 3x since last Feb. and thats when I noticed it doesnt seem to be working. I only had to use it for short trips so the main defroster in the cab eventually defrosted the rear window. The weather is warmer so now I wont have as many chances to have it fogged up. Any ideas as to what it could be? Im hoping for an easy fix.

Thanks in advance!

 

I'm not sure how the dealer checks it, but there must be some type of electrical connection in the wiring to and from defroster. Maybe you can check current draw with a current probe? Checking voltage might not work well since there is going to be a big voltage drop across the defrost grid whether working or not.

I also thought my defroster was pretty dang useless last winter. Not sure if it was working or not.

 

Soundwave I know what a pain it can be to figure out rear window defroster trouble. This is a bigger pain just after the warranty runs out. If you take it back don’t pay for new glass until you do a few simple defroster troubleshooting and repair steps.

I work for a company who makes defroster repair kits and we are frequently called on to troubleshoot customers rear defrosters. There are a few very easy steps to first determine what is broken and fix the rear window defroster.

The first step is to check the voltage directly on the two metal tabs located along the sides of the defroster. One of these tabs is ground and one is 12-14 volts power. Turn in the defroster and put the leads of your 12 volt trouble lamp, ohm or multimeter directly on the metal tabs. By testing directly on the metal defroster tabs you should see a nice bright illumination on a trouble lamp or 12-14 volts on a multimeter. If you see power on the tabs it means everything up circuit is working.

Next test with the leads right next to the defroster tabs but this time directly on the defrosters surface. You should again see 12-14 volts. If not this means there is a problem with the connection from the defroster tab to the defroster surface. This is an easy fix using the Frost Fighter Defroster Tab Bonding kit.

Frost Fighter 2000 Defroster Tab Bonding Kits

If there is no power at the defroster tabs then it means there is something wrong with the circuit. Disconnect the power tabs from the defroster and test again on the connectors this time. If still nothing check to see the status of the illuminated indicator lamp on the defroster control. This should be on when the switch is activated. If not check the defroster fuse.

There are a lot of guidance on how to repair a rear defroster on the internet including the Frost Fighter website under the Fix It page.

Defroster Troubleshooting and Repair Resource

We see a lot of tabs that are not making a good connection to the defroster and grounds that have gone south. A good way to test the ground is connect a heavy wire (14 awg or better) to the ground tab on the defroster and the other end to a known good ground on the vehicle temporarily bypassing the original ground to the defroster. If the defroster works in this set up it means the ground side of the circuit is bad.

I hope this helps.

Doctor Defroster

 

Thanks for your reply! Where are these tabs located? In the fuse box? Im not great at fixing things but Ill give it the ol' college try. I was wondering that because the dealer had to replace it once before, and even if my warranty has ended, if they'd fix the problem, seeing how my 3/36 warranty ended last Febuary.

 

The tabs are along the sides if the defroster, directly on the surface of the defroster, one on the right and one on the left typically. They look something like this image.

If the defroster tab is broken (and most are not) then I would replace it with a factory tab or one of the rear window defroster replacement tabs here

Frost Fighter Defroster Tab and Connector Replacements


It is definitely worth asking the dealer on this as well. Good luck

 

In my case on my 2014 F-350 it was the connections on the drivers side of the rear window for the center slider. One of them had come loose some how.... used the Dr. Defroster tab repair kit and back in business...



Inside point where center section / slider defroster gets its power. Main power at the two clips on the right.

Visually found broken connection.

Hard to see, but outside view of connections.

Outside view of broken connection point on left.

13.8 VDC with broken connection, and 11.75 VDC after repairs..

Repaired connection