robpenrose

New Member
Any ideas. I have one, but not sure if its working. The lights comes on when i hit the button, but dont seem to get any noticable results when its steamed up, and it hasnt been iced up properly yet to try that?
 
The one on my TD5 Discovery takes less than a minute to clear when misted and not much longer if its iced.
 
ok thanks. if its frosted tomrrow i will give it a go. Have a feeling its not working though. Bugger!!!!

Anyone got any common faults/ easy fix of what it could be?
 
i have a chip, but surely just the broken area wouldn't work. will have to check the fuses at the weekend, its too bloody dark when i get home.

If the fuse was fooked, would the switch light still come on?
 
i have a chip, but surely just the broken area wouldn't work. will have to check the fuses at the weekend, its too bloody dark when i get home.

If the fuse was fooked, would the switch light still come on?
Gorra chip in mine but that dont stop it.Minute max for really steamed up ;) Not tried it on ice yet but should be quick
 
Did a little check today, turned the back one on and i the revs dropped very slightly and a click sound from under the steering column, nothing happened with the front one so guess its not working.

Any solutions. Havent checked anything yet.

If there is no power getting to it, fuses/relay or something more serious??
 
fuses, relay, wiring to the screen (often come lose on rear screens in a lot of cars so guessing might be the same for front ones), switch, multi function unit,
 
I just checked the fuses, they are fine so its not them? Can i just pull the relay for the heated screens out or will it feck the electrical system up? (Does the battery need disconnecting?

Is there any way of testing the relay? EG with multimeter etc? Probably a very stupid question but dont know much about them!!!

Its ****ing me off especially as its cold at the moment.

The light still comes on in the cabbin and when the clear windscreen button on the A/C is used it also comes on but no heated screens, so surely the MFU is ok?? Its like there is no power getting to the element.

Any advice please??
 
There are 2 fusible links in the fuse box under the bonnet (No's 7 & 8) which cover left and right part of the windscreen (40amps each) have you tried them.
Relay R8 is the one for the screen - its 3rd on the right row from the front of the vehicle again under bonnet fuse box.

The folowing is from the electrical manual of the RAVe cd.

Heated Front Screen (HFS)
Heated Front Screen Description
The heated front screen (HFS) is operated from a non-latching switch located
to the left of the instrument pack. The switch has an indicator light to show
when the HFS is operating. The HFS comprises two elements laminated in the
screen, each element being controlled by a separate fuse. The HFS will only
function with the engine running, due to the high current draw and subsequent load on the battery.
The HFS can also be operated by the air temperature control ECU on vehicles
fitted with air conditioning.

Heated Front Screen Supply
Circuit supply
A feed from the battery positive terminal is connected by an R wire to the
engine compartment fusebox, where it passes through fusible links 1, 7, 8 and
fuse 13. Fusible links 1 and 7 are connected in series.
A feed from fusible link 1 is connected to the contacts of the heated front
screen relay in the engine compartment fusebox.
A feed from fusible links 1 and 7 is connected to the contacts of the auxiliary
circuits relay in the engine compartment fusebox.
A feed from fuse 13 is connected from the engine compartment fusebox to the Body Control Unit (BCU) on a PN wire.
A feed from fusible link 8 in the engine compartment fusebox is connected on
an NW wire to the passenger compartment fusebox and from the fusebox to
the ignition switch on an N wire.
Ignition switch supply
When the ignition switch is in position I or II, the feed from fusible link 8 flows
through the ignition switch to the passenger compartment fusebox on an LGW
wire. The feed continues through fuse 26 in the passenger compartment
fusebox and is connected on an LG wire to the coil of the auxiliary circuits relay in the engine compartment fusebox.
In this condition, the auxiliary circuits relay coil is energised and the contacts
close. The relay coil is earthed to earth header C0018 on a B wire from the
engine compartment fusebox, via header C0286 LHD/C0288 RHD.
When the ignition switch is in position II, the feed from fusible link 8 flows
through the ignition switch to the passenger compartment fusebox on a Y wire.
The feed continues through fuse 29 in the passenger compartment fusebox
and is connected to the BCU on a GU wire.
Heated Front Screen Operation
When the HFS switch is operated, an earth path is completed from the HFS
switch to earth header C0017 LHD/C0018 RHD on a B wire, via header C0760.
The completion of the earth path from the HFS switch, completes an earth path from the BCU to the switch on a KO wire. The earth path completes a circuit within the BCU for an internal electronic switch which receives its feed from fuse 29.
The internal switch closes, completing a circuit which allows the feed from fuse 13 to flow to the BCU on a PN wire, through the internal switch to the HFS switch. The feed illuminates the HFS switch indicator light and is earthed from the switch to earth header C0017 LHD/C0018 RHD on a B wire, via header C0760.
The feed from fuse 29 is connected to a second internal switch within the BCU.
When the HFS switch is operated, the completed earth path closes the internal switch. This completes the connection from the heated screen relay coil to the BCU on a KN wire. The earth path from the BCU is on a B wire to earth header C0551.
The completed earth path energises the heated screen relay, closing the relay
contacts, allowing the feed from fusible link 1 to flow through the relay contacts to fuses 7 and 8.
The feed from fuse 7 is connected to the LH front screen element on a PS wire.
The LH front screen element is connected to earth header C0017 on a B wire.
The feed from fuse 8 is connected to the RH front screen element on a PK
wire. The RH front screen element is connected to earth header C0018 on a B
wire.
The momentary operation of the non-latching HFS switch, signals internal
switches in the BCU to close. Electronics within the BCU holds the switches
closed for a pre-determined period or until the HFS switch is pushed a second
time.
Air temperature control (ATC) ECU operation
On vehicles fitted with air conditioning, the HFS can be operated when ’DEF’,
’feet/screen’ or ’screen’ is selected on the ATC control panel.
When one of the above selections is made, the ATC ECU provides a feed to
the HFS switch into the PS wire from the BCU to the switch. This illuminates
the HFS switch indicator light.
Simultaneously, the ATC ECU also provides an earth path into the KO wire
from the BCU to the HFS switch. This earth path allows the internal electronic
switches within the BCU to close, powering the front screen elements as
described previously.

Hope this helps - By my reckoning should only take you two minutes to solve your problem after reading this novice's guide to your front winscreen.

Enjoy!!

Failing that chuck a brick thru your windscreen - have autoglass replace like for like and that will tell you if its the screen thats faulty.
 
Just had a look, the relay is working i think because i can hear it click in when the button is pressed. Got a multi meter on the wires which go into the screen and didnt get a voltage coming in when the screen was on, so guess the problem is somewhere else and not the screen itself.

Any ideas where i need to check next? Would an earth fault cause both elements in the screen not to work?

I think it could be the main power not getting to the screen cause all the low voltage stuff seems to be ok, fuses, relay and cabin switch!!
 
Did a little check today, turned the back one on and i the revs dropped very slightly and a click sound from under the steering column, nothing happened with the front one so guess its not working.

Any solutions. Havent checked anything yet.

If there is no power getting to it, fuses/relay or something more serious??
Just a thought - make sure the screen hasn't been replaced with a non-electric one????
 

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