Can anyone help me out ?
I've got a renault laguna 2.0 rt on a 95 plate, The problem i have is with the heated rear windscreen. when i turn the demister on nothing happens. I've put a circuit tester on the heater and theres 12.3 volts running through it so theres plenty of power there. There isn't a drop in power when i turn it on either. this seems to be a common problem as a few friends and family memvers who own lagunas also seem to have the same problem. short of replacing the windscreen any ideas ?
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How and where did you measure the voltage at the heater element? If you measured it from one terminal to the other, then there's a break somewhere, probably where the terminal attaches to the element. If you measured it from terminal to ground somewhere else, then there is quite possibly a faulty ground connection. If it's a terminal connection problem I believe there's some silver loaded paint/glue that can be used. Other regular contributors can probably remember the name of it.
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As you can probably guess i'm not great when it comes to cars but i measured the voltage from ground and with the other tester probe on the heater itself. i also tested the element the same way.there is a continous circuit when the ignition is switched on also.
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With the HRW turned on, measure the voltage at various points -
1. At the supply wire connected to the HRW - should be 12-ish volts.
2. At the terminal the wire is connected to - should be 12-ish volts.
3. At the HRW element near where the terminal is connected - should be 12-ish volts.
4. At any HRW element half way across the glass - should be 6-ish volts.
5. Repeat 1 to 3 for points at the other end of the window - should be 0 volts.
If all these are true, check (4) for all the other elements.
If everything still checks out, your HRW is working OK.
Based on your description, my guess is the same as wowbagger's - a failure at the point where the supply terminal connects to the glass. The silver repair glue is available from Halfords, but I'm not sure if it is suitable for refixing a terminal to the glass if this turns out to be necessary. I did this repair on my 309 with a soldering iron, but I was a bit worried about applying soldering iron heat direct to the glass and the end result wasn't neat (though effective).
Ian
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I'll just add that resistance tests with an ohmmeter can be misleading because the supply wire will earth through the dashboard switch warning light when power is off.
Ian
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