Rear heated windscreen wont heat up

[C3Noob]

Rear heated windscreen wont heat up at all.
I have checked the fuse and its good, the orange light comes on and i have used granville electro connector to repair all broken lines including 2 that went right through to the glass,
i have also checked the wires at both sides of the windscreen and they are not picking up any power.

[C3driver52]

Rear heated windscreen wont heat up at all.
I have checked the fuse and its good, the orange light comes on and i have used granville electro connector to repair all broken lines including 2 that went right through to the glass,
i have also checked the wires at both sides of the windscreen and they are not picking up any power.

Hello C3Noob

You need to check for 'power to earth (12v)' and then check for a good earth (ohms test) on those connectors.

Don't just check across the two main connection points on the heated window as that won't find a bad earth and just looks like no power.


F10 in the BSI is the rear heated window fuse, check that too.


The cable to the boot lid (including the rear heated window) goes through a rubber boot that flexes, maybe the cable is damaged?

[C3Noob]

cheers for the reply C3driver52


my fuses are

F17 (40A) Heated rear screen i have changed it from a standard 40A to a maxi 40A but still the same

2007 to 2010 fusebox layout

ive not checked under the rubber boot as yet will do that tomm

[C3driver52]

cheers for the reply C3driver52

my fuses are

F17 (40A) Heated rear screen i have changed it from a standard 40A to a maxi 40A but still the same

2007 to 2010 fusebox layout

Of course, sorry., the later model

[C3Noob]

I picked this up today so i can test this, any chance you can explain a bit more what i need to do to test the windscreen, never used one of these before and a bit unsure.
i know i need to take of the 2 side trims to uncover the 2 connectors to the window but thats as far as my knowledge goes on this even after watching videos tbh
thanks

[C3driver52]

Basically some simple tests:


with the heater power off, set the meter to ohms

Red lead to one connector you have exposed
Black lead to the connection on the opposite side of the screen that you have exposed.

You would expect a reading in ohms, M ohms, K ohms or whatever ohms scale you set.

Note the reading (take a picture)


The other tests you can do is with the power to the screen on, it goes off after a while, do don't wait too long.

Set the meter to volts, say 20v scale, whatever you have that's close.


Red lead to one of the connectors you just used for the ohms test and black lead to a known good earth on the car, maybe remove the rear cluster to find one.

What's the voltage reading?

Do the same again, but check with the opposite side connector to the same earth.

Read the voltage, what is it?



With those 3 we can tell if power is getting to it, if the earth is bad and if the filaments are joined.


You can repeat the tests several times to make sure you get a true reading and not a fluke. It takes a bit if practice, so have a go.

Post your results and we can work out the next steps to take

[Ozvtr]

Basically some simple tests:


with the heater power off, set the meter to ohms

Red lead to one connector you have exposed
Black lead to the connection on the opposite side of the screen that you have exposed.

You would expect a reading in ohms, M ohms, K ohms or whatever ohms scale you set.

Note the reading (take a picture)

While you are doing this check for continuity to earth (chassis).
WARNING!!!!!!! The metal electrical contacts are glued to the heater with a VERY weak glue. Do NOT apply pressure to the contact it might break off the heater!!
I recommend probing the base where the contact meets the heater. Avoid applying pressure to the electrical connector or attempting to remove the connector.
Put one probe on the exposed heater connector (on one side of the heater) and one probe to an exposed metal part. Try the same on the other side. One side should have low ohms and the other should be open circuit (meter shows "OL"). If both sides show low ohms, there is a short to earth (unlikely). If both sides show OL there is no earth return.
The earth wire connected to the heater is green/yellow. The power wire should be mostly black, it might have a red or pink stripe.

[Ozvtr]

If the fuse is good Then you possibilities are;
Bad wiring from BSI to rear screen. (No 12V at the rear heater but continuity to chassis on other side of heater)
Bad relay in BSI. (same as above)
Bad earth point, just inside the roof of the car. (12V at heater but no continuity to chassis on other side of heater)
Bad earth wire from rear screen heater to earth point. (same as above)


I seem to recall another member with a similar problem and I think it turned out to be a broken wire inside the rubber boot connecting the hatch to the body of the car.
I'm not saying that's the problem here, however.

[C3Noob]

with the heater power off, set the meter to ohms

Red lead to one connector you have exposed
Black lead to the connection on the opposite side of the screen that you have exposed.

Ohms test

Red lead to one connector you have exposed
Black lead to the connection on the opposite side of the screen that you have exposed.

Voltage test

wasnt sure how to remove the rear cluster to find an earth as yet

Put one probe on the exposed heater connector (on one side of the heater) and one probe to an exposed metal part
done this and the reading stayed at 1 there was no change from putting the probe on to the connector to removing it

[C3driver52]

Mine is 1.6 ohms with red and black leads across the heater element.

Yours is 80 something ohms.

That is quite a difference between a working one and one that doesn't.



Are the two plugs pushed fully into the meter?

They look a bit proud