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Heated Screen Light Question #682845
13/01/21 12:28 PM
13/01/21 12:28 PM
Joined: Aug 2013
Posts: 13,398
Salisbury, UK
Peter J Offline OP
Formerly known as Aldermog
Peter J  Offline OP
Formerly known as Aldermog
Member of the Inner Circle

Joined: Aug 2013
Posts: 13,398
Salisbury, UK
The switch for the heated front screen is always illuminated when the switch is in the off position and the ignition is either on or off.
Like this, ignition off, HFS off.

[Linked Image]

If I turn the ignition off when the heated screen is on then the switch goes off, no illumination at all.

Is this "normal" on all trads or is it unique to my car?
If it is unique I wonder if it is the cause of the battery drain we have previously discussed.

Comments and suggestion would be most welcome.


Peter,
V8s are best....
Tarka the 'Otter Mog....2014 Plus 8
AMG C63 Estate.


Re: Heated Screen Light Question [Re: Peter J] #682851
13/01/21 12:41 PM
13/01/21 12:41 PM
Joined: Nov 2015
Posts: 3,173
Yorkshire
CooperMan Offline
Talk Morgan Addict
CooperMan  Offline
Talk Morgan Addict

Joined: Nov 2015
Posts: 3,173
Yorkshire
Peter, the switch is unfortunately not wired traditionally direct to the 'screen, but is just a trigger to the BCU that then sends power to the screen, I don't know if the light is a BCU feed or just earths through the integral bulb as you press it, but if on all the time that bulb is certainly draining your battery as is not LED but a tiny filament bulb


Jon M
Re: Heated Screen Light Question [Re: Peter J] #682852
13/01/21 12:44 PM
13/01/21 12:44 PM
Joined: Jul 2007
Posts: 18,726
Suffolk
John V6 Offline
Member of the Inner Circle
John V6  Offline
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Joined: Jul 2007
Posts: 18,726
Suffolk
Peter, I just double checked mine. Bear in mind my 2014 car is wired so the sidelights are on if the ignition is on.
With my Roadster then:-
Ignition off the switch is not illuminated
Side lights or lights on with the ignition off the switch is not illuminated
Ignition on the light is illuminated , I'm guessing that without the side lights hard wired it would be off until you put the lights on. That was I think the case in my S1 Roadster where the lights weren't wired to be always on.

Seems to me that could be your issue. On my S1 Roadster a 2006 car the switch was hard wired into the PCB.


JohnV6
2006 Indigo Blue Roadster S1
2014 Brooklands Edition Roadster "Brookland's Belle" #5 of 50
Re: Heated Screen Light Question [Re: Peter J] #682857
13/01/21 12:54 PM
13/01/21 12:54 PM
Joined: Jul 2007
Posts: 18,726
Suffolk
John V6 Offline
Member of the Inner Circle
John V6  Offline
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Joined: Jul 2007
Posts: 18,726
Suffolk
Peter if it is like my S1 Roadster the back of the switch has a locking tab to the PCB . If you turn that it disengages the switch from the PCB. Uncle Melvyn has a parts book for a 2018 +8. That shows a more conventional plug arrangement.
Switch parts

[Linked Image]


JohnV6
2006 Indigo Blue Roadster S1
2014 Brooklands Edition Roadster "Brookland's Belle" #5 of 50
Re: Heated Screen Light Question [Re: Peter J] #682864
13/01/21 01:28 PM
13/01/21 01:28 PM
Joined: Feb 2016
Posts: 3,411
East Harling, Norfolk UK
RichardV6 Offline
Talk Morgan Addict
RichardV6  Offline
Talk Morgan Addict

Joined: Feb 2016
Posts: 3,411
East Harling, Norfolk UK
Peter this is a copy of the heated screen schematic for the last Roadster's and likely other recent Classics. The switch itself shown surrounded by a solid line, is likely the same on yours.

[Linked Image]

The switch contacts (pins 3 & 4) send a momentary ground signal to the BCU every time its pressed. This toggles the screen power either on or off within the BCU. When switched on, a timer is also triggered which automatically switches it off after a fixed period.

The LED illumination is permanently on with ignition but has two intensities dependant on screen heater being on or off and achieved by the resistor within the switch. The BCU has total control of this light and its intensity.

I'm sure your car was designed to operate in an identical fashion but likely a BMW derived BCU so all bets are off as to the reason for your findings confused2 It would certainly contribute to battery drain though however tiny the current is. As a workaround try always turning car off with screen heater on to extinguish the switch light and see if if there is an improvement to your drain issue over time.

ETA: it occurs to me that a worst case scenario is possible whereby the heated screen itself is left on by an uncommanded action from the BCU when car is switched off. The BCU would dutifully illuminate the switch at full intensity but the screen heater itself would do an excellent job of depleting your battery. Can you therefore verify the following:
Is the screen heat on after switching off normally?
Is the switch illumination at full or reduced intensity?
Leave car for 20 minutes and check if timer has inhibited screen heat and switch illumination or at least reduced its intensity.

Last edited by RichardV6; 13/01/21 01:54 PM.

Richard

2018 Roadster - Red/Magnolia - "Morton"
1966 Land Rover series 2a SWB
1960 Velocette Venom
Re: Heated Screen Light Question [Re: Peter J] #682870
13/01/21 02:07 PM
13/01/21 02:07 PM
Joined: Jul 2017
Posts: 135
Cheshire
Chilliblu Offline
L - Learner Plates On
Chilliblu  Offline
L - Learner Plates On

Joined: Jul 2017
Posts: 135
Cheshire
Peter
I had the same issue in my 2014 Plus 4. I ended up taking it to Oakmere to resolve the problem. It was a replacement PCB I think in the end but it ended up costing me around £650. It did not seem to make much difference to flattening the battery etc. but it was just the annoyance of not knowing if I had left the heated screen on or had turned it off. (I have never used it). It did take Oakmere two attempts to fix but this was because the replacement part from the factory was also faulty. Hope you manage to get a fix.

Last edited by Chilliblu; 13/01/21 02:10 PM.

Andy
2014 Morgan Plus 4
Re: Heated Screen Light Question [Re: Peter J] #682878
13/01/21 02:39 PM
13/01/21 02:39 PM
Joined: Jul 2007
Posts: 18,726
Suffolk
John V6 Offline
Member of the Inner Circle
John V6  Offline
Member of the Inner Circle

Joined: Jul 2007
Posts: 18,726
Suffolk
Peter is it on a separate fuse? Taking that out & carrying a cloth to wipe the windscreen might be a short term work around.


JohnV6
2006 Indigo Blue Roadster S1
2014 Brooklands Edition Roadster "Brookland's Belle" #5 of 50
Re: Heated Screen Light Question [Re: Peter J] #682882
13/01/21 02:46 PM
13/01/21 02:46 PM
Joined: Aug 2013
Posts: 13,398
Salisbury, UK
Peter J Offline OP
Formerly known as Aldermog
Peter J  Offline OP
Formerly known as Aldermog
Member of the Inner Circle

Joined: Aug 2013
Posts: 13,398
Salisbury, UK
Thanks, everyone!

I know the heater works, using the car in winter, hood up, this is easy to check. I didn't know it had a timer... I'll investigate further.
If the timer is in the relay it might be worth changing the relay and fuse, just in case and a LOT cheaper than the switch board.

When the screen is on the light glows brightly.

I've turned the ignition off with thw screen heater on, we shall see what happens.

More to follow..


Peter,
V8s are best....
Tarka the 'Otter Mog....2014 Plus 8
AMG C63 Estate.


Re: Heated Screen Light Question [Re: Peter J] #682890
13/01/21 03:48 PM
13/01/21 03:48 PM
Joined: Feb 2016
Posts: 3,411
East Harling, Norfolk UK
RichardV6 Offline
Talk Morgan Addict
RichardV6  Offline
Talk Morgan Addict

Joined: Feb 2016
Posts: 3,411
East Harling, Norfolk UK
Peter the control for your heated screen and many other non engine functions is likely in a sealed BCU as with the later Classics. Doubt you will find any external relay or PCB for this function. Good luck with your further checks. On the bright side you may have found the source of the battery drain even if you can't fix it. As suggested there is a dedicated 15 amp fuse for the screen - fuse #26.

Just speculation your car has a timer as well but our (BMW) Mini has for heat on both screens.

Last edited by RichardV6; 13/01/21 04:40 PM.

Richard

2018 Roadster - Red/Magnolia - "Morton"
1966 Land Rover series 2a SWB
1960 Velocette Venom
Re: Heated Screen Light Question [Re: John V6] #682909
13/01/21 05:23 PM
13/01/21 05:23 PM
Joined: Nov 2015
Posts: 3,173
Yorkshire
CooperMan Offline
Talk Morgan Addict
CooperMan  Offline
Talk Morgan Addict

Joined: Nov 2015
Posts: 3,173
Yorkshire
Originally Posted by John V6
Peter is it on a separate fuse? Taking that out & carrying a cloth to wipe the windscreen might be a short term work around.

Ahh, the analogue solution to the "all posh Mogs do that sir" grin2


Jon M
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