75ZT Community

Have you tried the indicators with the lights on it may make no difference due to the canbus system but it might. I ask because this sounds like an inadequate earth which on standard electrics results in lights flashing with indicators. On this system it would just confuse the ecu with varing readings. Have you had the battery fully disconnected for 45 minutes to let the ecu's reset cures a lot of things.

Derek

Thanks Derek, Yes! the indicators are working normal.

I've had battery disconnected for half a day, so thought that would have reset what it needed to.

I have just gone out and checked again, straight away the brake lights come on (dim) and no normal rear lights. I gave each light unit a tap and brake lights go out and normal lights come on, I then stitched everything off and then turn lights back on again and all is working fine.

I wait a minute and try again and we are back to square one (brake lights back on and no normal rear lights) give another tap and hey presto! brake lights go out and normal rear lights come back on.

Today I've had N/S brake light on with no rear light and O/S normal light on with no brake light, its been light this for days now.

Just for clarity, this has nothing to do with the Canbus system as that is used between engine, ABS (Antilock Braking System), instrument panel, and auto gearbox.

A poor earth is a suggestion that has been discussed, but the symptoms would be similar. Also tapping the lamps wouldn't fix it unless it was inside the lamp which has been checked.

Oh and Sorry, ended up not getting out to the car, been searching for other things.

Now here's a thought. You can leave the wiring connected but pull the bulb holder out of the lamp. Then try wiggling things to see if you can make the fault come and go.

Duncan wrote:Now here's a thought. You can leave the wiring connected but pull the bulb holder out of the lamp. Then try wiggling things to see if you can make the fault come and go.

Yep! done the wiggling of the plug Duncan and it sometimes triggers the brake lights to go out and normal rear lights to come on (just as the tapping does). I've tried five 5Watt bulbs and the fault is still present with each bulb, so it cannot be a bulb problem.

I've just checked again and the fault light-out dash icon is back on, but all lights are working fine. I will check again in a minute or so and I bet brake lights come on and no normal rear lights (not until I give em a tap).

Can anyone go out to their car and just switch on there ignition and turn their lights on, then just unplug one rear light (wait a 2 seconds) then plug back in again and see if their brake lights come on first and then go out, then normal rear lights come on. Easy to do, just pull of one rear light unit cover in boot then pull plug out (takes seconds).

Cheers fellas.....

OK, car will probably not start now, but the lights did this:

All my lights work fine. Unplugged RH unit, switched on lights, only LH cam on (tail only, no brake). Plugged in RH, tail came on, and so did dim brake. After approx 2 seconds the brake goes out again.

This is no real surpise. The light switch module tries to power the tail lamp and realises theres a fault so tries to power the brake lamp dimly. When you plug in, they both come on, but the light switch then sees the tail lamp and switches off the brake lamp.

Yours is slightly different, in that the tail lamp doesn't come on at first with the brake lamp. But then it doesn't do that anyway when you switch it on. Do you have a multimeter to check the voltage at the connector to get an idea what's going on?.

Thanks Duncan, you're a gem.

Well that explains that one then, my system is obviously sensing both tail lights are 'OUT' which is activating the brake lights in DIM mode. I have change all bulbs and still this happens on both sides, either one side or the other (and now both sides at the same time).

Why would tapping them have an impact on turning the brake lights out which then turns the normal rear lights on, as said this happens on both sides (I have checked the earth wire on inner rear wing behind carpet) all is ok.

.................... and no I sadly do not have a multimeter

I suppose the first port of call would be to replace both rear bulb holders, then the wire loom plug.......

Thank you for your help Duncan....

Dallas wrote:Thanks Duncan, you're a gem.


I suppose the first port of call would be to replace both rear bulb holders, then the wire loom plug.......

But how can both bulb holder units be faulty at the same time I ask myself......

Tapping them turns the tails on, which switches the brakes off, is my guess.

Is it an instant change over, or do the tails come on, then the brakes go out after a short delay?

Duncan wrote:Tapping them turns the tails on, which switches the brakes off, is my guess.

Is it an instant change over, or do the tails come on, then the brakes go out after a short delay?

If I turn lights on via switch and have one or both brake lights on (dim), then tapping light unit brings on normal rear light/lights which then switches off brake light/lights within 1 to 2 seconds.

Another format! both rear lights are on as normal but I have the light out icon on the dash, so I unplug wire loom plug from bulb holder and then plug back in (this then brings the brake light on first then the normal rear light (then brake light goes out) and so does light out icon (BUT! I have had rear brake light on and normal light on at the same time on one side) and light out icon stays on.

These combinations happen on both sides......

If lights have nothing to do with canbus why do we have to have relay for towbar socket and canbus compliant led bulbs for the mg7 lights. The light switch unit is a ecu I believe. Do you have a towbar?

Derek

swinnie wrote:If lights have nothing to do with canbus why do we have to have relay for towbar socket and canbus compliant led bulbs for the mg7 lights. The light switch unit is a ecu I believe. Do you have a towbar?

Derek

We don't have CANbus compliant LEDs, they are a complete misnaming. Yes, the light switch is an ECU (Engine Control Unit), but it isn't connected to the CAN (Bus Controller Area Network) bus, only to Kbus. The lamps are completely conventional one wire per function. What CANbus leds really mean is they include a load resistor to ensure the bulb failure monitoring isn't triggered. Controller Area Network (CAN) is never directly connected to any bulb or LED (Light Emitting Diode), it's a way for ECUs to talk to each other, and on the 75, only the ones I mention use it. On some other cars, CAN is used for communication between other ECUs which include whichever ECU drives the lamps. This tends to co-incide with cars where bulb failure monitoring is included, and my guess is that they have become misnamed because of this.

Yes, I have a towbar on both my 75s with the official Rover (BMW) towing adapter. This is not on CAN bus either, and is not actually a relay but another ECU.

Guys, went to scrappy today to find no rear light clusters, just a Tourer sitting there looking all very unhappy for itself. Funny thing is last week they had two 75 saloons would you believe it.

Anyways! I have had my clusters apart again today and cleaned them up even though they are already clean used more WD40 and been lightly sanding the metal contacts here and there and guest what ? .......................... the lights seem to be working as they should, I wont count my chickens just yet but hope all is sorted.

Will keep an eye on them........

Cheers fellas.

And if you go to Maplins you will buy a multimeter for just a few pounds - worth their weight in gold when you have problems.