Rear Defroster/Defogger

I can't say if yours is broken or not but I know mine reacts similar to yours. I put it down to the top screen being glass and the bottom one being perspex/plastic. I also notice that the gap between the elements is wider on the bottom screen, so maybe the perspex heats up quicker than glass?

 

It is possible that the back window may defog quickly when the front defroster fan is on Max w/ outside air. In Hawaii where morning temp in winter can match the dew point, all of the windows can fog up instantly and one is driving totally blind. This is why you will notice the natives always driving with thier windows open. Native: People that live in Hawaii. It's all about air flow past the glass.

 

Silly me, I thought this was because those cars needed a recharge of Freon...

I think that Grumpy is on the mark.

 

I agree, but I would not depend only on the window elements. Pat you are not that silly!

 

Digging out of the seventh snow storm (and it's not even winter yet) in Minneapolis and I've put the rear defroster through its paces. I thought something must be wrong with my car which was new in April -- the upper defroster is very slow and even downright ineffective.

These other postings lead me to believe my alternate theory -- Prius has to be miserly in its distribution of current to accessories. I believe it is underpowered by design.

It's going to be a long winter.

 

I had a similar issue. My upper defogger stopped working completely. I took it to the dealer and he finally figured out that it was a faulty resistor. After they replaced it both defoggers were working.

 

I am having the same problem, the top window are not defogging well as the lower one. I took it to a dealer near by me and the service advisor swears the defogger lines are radio antenna and the prius dont have defoggers. That all the cars back window lines are radio antennas........I do have windows tinted, hope it can be fixed without removing the tint. obviously at a different dealer.

 

If you are looking at this because your 04-09 rear defrost is not working note my 2005 (240K in Fall 2016 Midwest) rear defrost operation was restored by fixing an overheated connection between the wiring and the heater on the glass on the passengers side bottom right corner under the black plastic trim between the top and bottom of the window.

Got to love a visual inspection providing bread crumbs.

 

OK, I'm facing the same issue here...my connecting wire was burnt/brown, although it was still delivering current. I briefly got the grid to work by jumping the connection (stuffed a little tin foil under the tab to the grid), but the connector got hot to the touch and then the defroster tab popped off after having it connected for a few seconds.

Obviously I have to re-connect the rear defroster tab to the grid. But do I need to replace the connector, too? I know the resistance of the grid should get warm, but is it normal for a connector to get that hot? Daveatm14, if you see this, did you have to replace the connector itself?

 

You had a loose fit between the connector terminal, and the tab on the grid. Poor fit equals high resistance which causes heat when current flows through it. That caused "burned" looking wire and the tab to "desolder" - pop off.

Repair can be a little dicey. Replacing the wire and connector is easy enough (you want an OE connector). The fun part is the tab. I think the aftermarket has a kit out there to glue it back on and conductive paint to make functional.

I don't know what the factory used originally. I found GM service bulletin # 03-08-48-006J which mentions using (silver bearing) solder to reattach tabs on their cars' defroster.

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