Interior light / headlight warning buzzer

  1. My model of MX-5 is: 2013 Sport Tech PRHT
  2. I’m based near: Sunderland
  3. I’m looking for technical help or recommendations on: my interior light and headlight warning buzzer.

Got a couple of little problems which I would love some help with.

Firstly my interior light has an irritating problem. The light will illuminate if the passenger door is opened but not the drivers door. Thinking the door switch was the issue, I swapped them over but still only the passenger side one works. Has anyone experience this?

Secondly, when I leave my headlights on and removed the keys and open the door, I used to have a buzzer going off to remind me the lights were on, for some reason this has also stopped.

Any ideas how to sort this as I am puzzled?

Sounds related
Are you getting power to the door switch??

Not 100% sure as I don’t have a multi meter to check

You can check with a 12v bulb

Only one wire goes into the plug which goes into the switch.

You’ve rightly identified that there is something wrong with the drivers side wiring or connection. Having swapped the switch over and had the same symptoms we can rule out the switch as the problem. That leaves either the wire back to the lighting circuit or the quality of the negative connection. Often this is where the screw that holds the switch in the door frame and makes the connection has rusted and no longer gives a decent connection. First job would be to clean up the screw or replace it with a similar and to clean the screw hole. Once these have been cleaned we can eliminate the switch side entirely and concentrate on the wiring to the lighting circuit, for this you will need a multi meter. They are cheap as chips these days so go to your favourite online tat retailer and order one up

Not sure if the actual switch surround is the earth

Aldi are doing multimeters for a tenner right now.

The OP has said that:

so it’s very likely that the switch surround does act as the earth.

On most similar circuits that I’ve worked on, closing the door pushes in the plunger which breaks the circuit and switches off the internal light.

I’m with bettabuilda on the earth.
If there’s a self-tapper holding the switch in place, that is almost certainly the earth.
Using the surround as an earth would involve having lots of bare metal for it to earth to and that would seriously promote corrosion.
It might be as simple as replacing a nasty rusty screw with a nice shiny one.

You can see the metal part of the switch, which the screw connects to the door frame to make the circuit.

(I can’t see where bettabuilda has contributed to the thread?)

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My bad.
It was BrilliantBlackBirdy.
Apologies all round.
I get even more easily confused these days… :frowning:
All those bees :honeybee:

Yes that’s the exact switch. The plastic part is actually rubber.

The screw isn’t rusty but I will have another look tomorrow

But having said that when I have changed the switches over the driver’s side works in the passenger. So I don’t think it’s the switch

Quite so.
It would appear to be either the power to the switch or the earth.

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This is the exact same problem I have, which I wrote in this thread:

I’m glad it’s not just me.

Have you had a leak from the scuttle grommets? This can drip into the locking control module to the left of the glove box. The buzzer is driven from this box. Look for rust lines where the water has been running!

The leak can upset other things as well!

I can’t suggest anything for the light switch though except a broken wire or bad connection.


Presumably you had no power to the switch then…

There’s 0.5/0.6V on the wire to the switch when metered to ground.

That’s interesting.

Half a volt or so. Do you know how much you have on the other side, which presumably works ok??