Odd courtesy light problem

[Dashnine]

I have a strange problem with the drivers (right) courtesy light on my MG ZT 260 that doesn’t seem to fit other experiences people have had!

The light works fine using the manual switch, but doesn’t respond at all to the doors opening. The main and passenger (left) lights work as expected both manually and with the doors.

I’ve tried the 10 second press of the main courtesy light button to no avail. I realise the next step is a battery disconnect for 30 mins to reset the ECU, but as I have an aftermarket Alpine CD / radio and I don’t know if it’s coded or not (I don’t have a code), is there anything else I could or should try first?

[suzublu]

Have you checked the bulbs?

Sent from my SM-A326B using Tapatalk

[Dashnine]

Originally Posted by suzublu

Have you checked the bulbs?

Sent from my SM-A326B using Tapatalk

“The light works fine using the manual switch”

[bsafly]

Might be worth checking the switch contacts on the o/s courtesy light or possible poor or loose connections to the switch.
As you state the door switches and remaining courtesy lights operate as expected this suggests the fault lies with the one that doesn’t work correctly.

[Dashnine]

Originally Posted by bsafly

As you state the door switches and remaining courtesy lights operate as expected this suggests the fault lies with the one that doesn’t work correctly.

And this is what’s puzzling me - the o/s light switch works (the light comes on independently from the left and centre light). The door switches work as the left and centre lights come on when the doors open.

So both switch’s (roof and door) work, the light works itself - but just doesn’t come on when the door opens. Bizarre! So maybe it’s whatever tells the light to come on when the door opens - doesn’t work, i.e. the ECU.

[bsafly]

I am assuming the 260 courtesy light is the same as the rest of the 75/ZT models.
I don’t have a specific wiring diagram, but the spare unit I have only has one wiring connector which feeds the light unit so if one particular light is not responding then it can only be a poor switch contact or circuit board fault, there is no designated wiring for each side of the unit.

[Dashnine]

Originally Posted by bsafly

I am assuming the 260 courtesy light is the same as the rest of the 75/ZT models.
I don’t have a specific wiring diagram, but the spare unit I have only has one wiring connector which feeds the light unit so if one particular light is not responding then it can only be a poor switch contact or circuit board fault, there is no designated wiring for each side of the unit.

Thanks, that’s useful to know. As the switches all appear to work, then it must be the ECU so a 30 minute battery disconnect seems the next thing to try.

[bsafly]

Picture of circuit board on courtesy light (borrowed from the internet) showing the one connector that supplies all the lights in the front unit, if the centre and left lights respond to the door switches, it must be a fault with the circuit board or switch contacts (switch has three positions: on, off and door switched).
If there is a 'dry' connection in the circuit board or the 'door switched' contact within the switch has a poor connection, the light will not work in that position.
If the n/s and centre lights respond to the door switches then the ECU must be operating correctly.
Hope that helps.

[Dashnine]

Thanks again, so it maybe (hopefully) that the roof switch isn't connecting in the ‘off’ position to the power supply from the ECU (reacting to the doors opening), but connects OK to the power via the ‘On’ position.

So tomorrows job is to take the light assembly off and have a look!

[SD1too]

Originally Posted by Dashnine

Thanks again, so it maybe (hopefully) that the roof switch isn't connecting in the ‘off’ position to the power supply from the ECU (reacting to the doors opening), but connects OK to the power via the ‘On’ position.

So tomorrows job is to take the light assembly off and have a look!

I've had a look at the circuit diagram (for the 4 and 6 cylinder cars). There are three connections to the front interior lamp unit, all of them from the BCU. The fourth (B) is a hard wired earth common to all three bulbs.

PW supplies one side of both map reading light switches and PS supplies the other side. So I think the driver's side switch is the prime suspect at the moment, as you've said.

Let us know how you get on please Phil.

Simon