Technical Bottom half of heated rear screen not working

[Mercedes]

When I bought my car last Summer I didn't think to check the heated rear screen. So it wasn't till the weather got cold and I used it that I realised the bottom half of the screen doesn't work. As we didn't have a particularly bad Winter I just left it but now it's October I'm beginning to wonder if maybe I should have it fixed.

My husband said it will need a whole new rear screen and will be expensive and not worth doing, he thinks having half the screen working is enough. He has had a look at the elements and can't see any breaks or scratches so we aren't really sure what's wrong with it

I don't really want to keep chucking money at the car as I've already paid to have sensors put in, had a dash cam installed and now someone on a pushbike has gone along the side of the car and put a dent about 14ins long along one side

Lyn

 

[John202020]

Have you got a "multimeter" with sharp prongs ? use the meter to see if there is a voltage at the base of the thick side bars( from where the horizontal ones come from) may have to gently rub the sharp prong against the track, next see if on the other side there is a good earth at the base, this is to see if the track is broken going down either side stopping all lower ones working? this would be possible but rare, most likely is something that's swiped up scratching through the tracks when closing the boot lid.
Look from the outside for breaks in the tracks VERY closely, the break can be thinner than a hair and may look like a slightly different color line/break, not a easily visible break, it may take several looks at the same track to find it, problem is if its where the black boarder is then you can only look from inside and it may not be easily seen under the enamel but given several are broken it maybe possible to see.
If you can find the break then its possible to repair with conductive paint, care is required though to use it.
Of course it could accidentally break an require replacing using the glass cover on your insurance?

 

[typecastboy]

There's going to be a break in it somewhere. Look closely and you can get a conductive paint for bridging the gap.

 

[John202020]

Just had a quick look the power is fed from the base of the screen meaning it's not the vertical tracks that's failed so it's highly likely that it is a case of something cutting through the lower tracks , if you have one use a "eye glass" that a jeweller would use say to look extremely closely at the tracks, bet if you find it the next one up/down is broken in the same place.

 

[portland_bill]

As above, there will be some tiny cracks in the elements, quite likely all together, and maybe some marks on the glass as well. usually caused by contact from abnormal luggage.

Once found, they can usually be repaired, using this:http://www.halfords.com/motoring/paints-body-repair/adhesives/granville-rear-heater-repair
It's a messy operation, as any brush will be enormous compared with the element, but usually successful.

 

[John202020]

As above, there will be some tiny cracks in the elements, quite likely all together, and maybe some marks on the glass as well. usually caused by contact from abnormal luggage.

Once found, they can usually be repaired, using this:http://www.halfords.com/motoring/paints-body-repair/adhesives/granville-rear-heater-repair
It's a messy operation, as any brush will be enormous compared with the element, but usually successful.

The trick to a neat job is to mask either side of each track with a plastic tape use a hair dryer to dry it and remove tape quickly in order it does not look like some child with lipstick?

 

[portland_bill]

The trick to a neat job is to mask either side of each track with a plastic tape use a hair dryer to dry it and remove tape quickly in order it does not look like some child with lipstick?

Great description. I've done two of those now.
I've tried masking it with normal masking tape, sellotape, and insulating tape. No success. If left too long, removing the tape removes the paint, if removed early, the paint tends to move a bit. So I've just lived with a few blobs and a working window.

I've had a pack of the stuff waiting for one or two lines on the Panda, but with the aircon on at all times, it doesn't mist up, so can't remember the last time I used the rear window heater. It'll probably go off in the tube before I get around to the job.

 

[Maggie]

Great description. I've done two of those now.

I've tried masking it with normal masking tape, sellotape, and insulating tape. No success. If left too long, removing the tape removes the paint, if removed early, the paint tends to move a bit. So I've just lived with a few blobs and a working window.

If you go to a hobby/ model shop, they sell a paint on rubberised liquid mask that peels off once dry. It's comes in a small triangular bottle and the lid has a built in applicator brush, I think it's made by Revel.

I previously used it to mask up areas of delicate painting jobs where it was impractical to use masking tape. Including successfully painting a section of glass.