Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) Flashing heated screen switch

Hi All. I have a 2014 plus 4 GDI which I bought two years ago. The car is great however since I have had it the switch for the heated front screen constantly flashes on and off.

I have taken the car into Oakmere for a fix in September last year and they told me a board needed replacing behind the dash. At a cost of several hundred pounds I had this work undertaken and it seemed to solve the problem.

I have not used the car over the winter and starting the car last week the problem has returned. The light flickers on all the time. Key in the ignition, key out of the ignition. I came to start the car this morning and flat battery. The car has only been off the trickle charger for a week so I think the switch is also flattening the battery.

Any ideas anyone. Obviously I can go back to Oakmere but I am reluctant during this COVID period and they will probably charge me several hundred pounds more for whatever is next on the list to cure it.

I am not an overly technical person so I don't want to be dismantling the dash but if there are any simple cures please let me know. I thought about just removing a fuse but I am unaware what else would be on the same circuit. When Oakmere replaced the board they told me it had also caused a problem with rear fog lights.

Thanks for any help.

It appears to me that changing the board was in fact the correct cure for the problem. They are of notoriously poor quality, often in short supply and cost somewhere north of £500. It looks as though the replacement has failed again and should be replaced without charge.

Would have thought the power supply to heated screen would be via "run" position on ignition switch. If so there is something more sinister at play, maybe the BCU.

On my Roadster the BCU controls the power to the screen heater and the switch is just a trigger for this. A further push of the switch cycles it off or it simply times out. The switch has its own illumination, dim or bright depending whether screen heat is on or not. Does yours function in similar manner when working correctly?

Hi Richard.
Yes mine works the same as yours. At the moment when I press the switch in it goes a slightly brighter colour then when I press again to turn it off. Unfortunately it is never off completely even when the keys are removed from the ignition. Like you say I expected removal of the keys to kill the switch but seemingly not.

Don't know whether it helps but this is the wiring for same on my Roadster Andy.



As you can see a part of the BCU is fed by a fused ignition switch (run position) feed to power the screen itself, with the momentary switch commanding the BCU to turn on heating for pre-set time or until it receives another momentary command to toggle off.

You will also note the switch lighting (dim or bright to indicate off or on) is directly under the command of the BCU, not the switch itself. I can see from the Plus 4 chassis loom diagram that yours is also BCU controlled, and your comments suggest it works in the same manner. It seems therefore the BCU or its connections are responsible for the problem not the switch.

Would be interesting to hear what Oakmere have to say on the issue. I would be tempted to say pulling fuse 10 in the body fusebox will kill all power to the screen and save your battery but for the fact it appears to be powered with the ignition off

ETA: have just checked and the Plus 4 connections to the BCU for control of heated screen are identical. If not the BCU then an intermittent short to earth on the orange trigger cable to BCU pin B14 would simulate a button press and cause the issue. Following on from this the issue could after all be an intermittent short in the switch itself or the PCB it sits on and the BCU is just blindly doing what it's told. Any signs of water damage? If not I think you have a strong claim with Oakmere.

Unfortunately none of this explains why the screen is ever energised with ignition off unless of course the BCU is at fault

Good luck. I would go back to Oakmere.
My switch is lit when the ignition is on and lights up more when it is switched on. It isn't on when the ignition is off.
The only light that flashes with the ignition off is the immobiliser.

Thanks all I think a trip back to Oakmere. I called them yesterday but they were still in the middle of setting up their COVID operation. they said they will call me back at some point!!!

Thanks for update Andy. Please let us know the outcome, particularly the cure.

Just an update. I took the car back to Oakmere and they diagnosed it was a PCM replacement that was faulty. This is what they changed last year. The repair was completed with no charge. I have to say Oakmere were very good and the car is now back and working correctly hopefully for a while this time.

Check you don't get water in the indicators, it is said that can cause them to fail. Also make sure water isn't getting into behind the dash via the wiper mounts or other grommets.