Does the rear window defogger only work with both side terminals connected?

I observed that one of the terminal of my rear window is broken, so is it that now it wont even defog half of the screen? Or it works only if the other is connected as well?

  • 1
    Difficult to tell what you're talking about. Rear defogger must have at least two wires coming to it (might be on different sides). Could be made of multiple parts as well, so multiply that. If by "broken" you mean "cut off" then it will definitely cause problems. Commented Feb 18, 2016 at 8:10

2 Answers 2


The rear defogger must have two connections. It works off of DC current and needs a positive connection and a negative connection in order for the electrons to flow and create heat. There are some kits out there which might help you to get this fixed, but I've never used them and don't know their voracity. They basically re-link the broken side back into the matrix which provides the continuity for it to work.

  • Could the rear defogger be grounded to the chassis in some hidden way, and you only have the positive terminal to hand? Commented Feb 18, 2016 at 12:53
  • Pretty unlikely. The earth connection would have to go through the beading.
    – Chenmunka
    Commented Feb 18, 2016 at 13:08

Rear window defrosters/defoggers can be configured in several different variations. The most common have a + positive wire going in one end of the grid and a - negative (ground wire) going to a metal part of the frame. This completes the circuit. The ground wire is usually on the opposite end of the (+) grid, but can be on the same side depending on how it is wire to the grid.

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