Rear Screen not working

[Sockrancher]

Hi All
As the thread subject says.. Fuse ok, rear screen matrix ok, but only 2vDC at the rear screen connectors. I can hear the relay switching when I turn the heater on and off, but I can find the damn thing - someone point me in the direction of the Rear Screen Heater Relay? Or better still post a wiring diagram of the heater system?
Many thanks in advance..  Chris

[Sol]

It's built into the PCB of the BSI computer in the dash, buried behind the wiring at the back of the glovebox. Very complex to swap, even if you can identify which one it is. Little to no documentation exists on which is which.

[Sockrancher]

Thanks Zion.. It's weird that I've only got 2v at the heater; points to a PCB problem maybe. I might have to come up with a Heath Robinson solution.  If anyone has a wiring diagram I'd be super grateful.. It's a 2009 1.6 LH drive with the TU5 motor.
Chris

[Sol]

If no one else posts, I'll try to remember to dig that schematic out at work on Monday. I don't have access to ServiceBox at home so can't help until then.

The big problem on these vehicles is all switches and buttons go to the BSI multiplex computer. It then in turn, operates a relay by turning on an output.

So jerry-rigging is really hard for most things. You could stick a switch in with a fuse and a relay hooked up to the rear window, but also the BSI has a timer so the heated screen is not on permanently.

Electronic engineering is my trade, and I'd think three times before stripping my own BSI down. But, It's doable, if you have the kit and the skills, to repair it.

[oilyrag]

If you are considering by-passing the problem then one of these - a relay with a ten minute timer, designed to operate with 'ignition on' could do the job. 
https://www.12voltplanet.co.uk/12v-unive...delay.html
   

[Sol]

Here, I like that site Oilyrag, good find.

[deejay_xb]

are you sure that the rear screen heater operates with 12v? maybe it has lower voltage, just asking..

[Sol]

@Sockrancher Do you have manual air con, no air con or automatic air con?

Ok have made assumption of manual air con, rear tailgate with opening window (ServiceBox asks these variants)

Attached schematic below:

  B9 Heated Rear Screen.pdf (Size: 127.64 KB / Downloads: 6)

Looks like F17 feeds relay R8 and then onto the rear screen, the relay coil is 8V not 12V but the sceen itself is 12V since F17 is fed from F11 which comes from the ignition switch live. The BSI controls the relay of course. Connection to the rear screen is pins 1&9 (joined together / bridged) on plug 16V NR from the BSI (16 pin black plug) to the heated screen, with the other end of the elements grounded locally.

All fuses mentioned are on the BSI itself.

BSI Fuses:
   

BSI plug layout:

  BSI1-2.pdf (Size: 172.9 KB / Downloads: 3)

[oilyrag]

are you sure that the rear screen heater operates with 12v? maybe it has lower voltage, just asking..

As the HRS only works when the engine is running it operates on mine at around 13.5 volts (alternator voltage).

[Sockrancher]

Hey thanks for all the replies and for the diagram Zion. I'll check it out this weekend. It's manual a/c. I'm ok with wiring diagrams and troubleshooting (Avionics B2 Engineer)   It's just access to the BSI that's a PITA.
Chris