Interior Light unfortunately not working

  1. My model of MX-5 is: Mark 3.5 1.8 SE Roadster
  2. I’m based near: Cardiff
  3. I’m looking for technical help or recommendations on: Interior light

Hi all,
Just bought my first Mazda MX-5 - a 3.5 SE roadster.

Loving the car, but struggling with the interior light.
Here is the story.

Light not working when car purchased.
Tried a new bulb, which did work, but was a silly colour.
Tried a white bulb, saw the spark when it shorted, and blew the Room circuit fuse under the bonnet.
Panicked when the roof wasn’t working, but changed that fuse, and everything apart from the interior light was working.
Swapped bulbs again, and cannot get the interior light working.
My illumination fuse inside the car looks ok. Will try swapping that anyway.

All I can still think of is to change the light itself.
Is his plausible? Is it easy enough?
Any other ideas?

Many thanks,

I would try the “new” bulb again and see if it still works. If it does it appears the “white” bulb is/has a problem.
If the “new” bulb is an OEM type bayonet one they can require a bit of rotating sometimes to get in the right position to work.
Is the light’s switch in the correct position?

Have you checked the fusebox in the passenger footwell?

My latest bulbs were Osram ones, of the type the car should take.
I bought a pack of two, and could not get either working.
I did move the switch to the ‘on’ position.

Would it be the ‘illumination’ fuse in the footwell?
This one looks ok, but I have ordered a replacement to try just in case it isn’t.

If you know someone with a multimeter it’s very easy to check a fuse.

Chances are the switch up beside the light is damaged.

You can check if the two door switches are working OK by simply looking at the door-open LED on the dash and opening each door in turn, ignition off.

  1. If the LED lights for EACH door on its own those switches are OK, the instrument cluster logic is OK, and the wiring up to the roof light should also be OK. Phew, examine the roof light and its switch more closely for mechanical/burn damage.
  2. If only one switch lights the LED, then it could be a faulty/dirty door switch, fiddly but cheap, or damage in the cluster, very fiddly and expensive.

When you see how weedy and make-shift the roof light and its switch are you will not be surprised how easily it can be damaged. It might even be possible to repair it by bending bits “straight” again or cleaning up burnt bits. But pull the Room fuse before fiddling with it again.

If you have a Volt meter, and know how to use it then these circuits below should help pin-point the problem. If you are in the least bit unsure it is better and probably cheaper to call the auto electrician.

Here is the circuit around the ‘map light’ switch
Here is the more complicated bit involving some logic in the instrument cluster for the other door switch. The LH and RH might be swapped over because this is a USA drawing, but you should get the idea.

EDIT corrected the link for the second diagram.

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Thank you for that - will try this all out.
If the light unit itself is a problem, a new one can be had for about £20, so I will just do that,

Mine blew in my NC 3.75. Tried everything I could think of before asking the local Mazda JCT dealership to look at it. They couldn’t mend it either!! so have given up on it.

I’ve been a bit of an idiot as it goes.
I bought on eBay several bulbs, suitable for the NC. However, it turns out they were too long.
The bulbs I bought were 38 or 41 mm long, and I think (while I might just squeeze a 36mm bulb in there), the requisite size is 31mm.
The 41mm bulb had an aluminium heat sink across the back, which came into contact with both electrodes, and hence caused the short circuit.
The conventional bulb (38mm) is too big to connect both electrodes concurrently.
So I have ordered a 31mm bulb, which I’m hoping does the trick.
The light fitting itself appears to be in very good condition, so I am not suspicious of a problem there.
So much easier when you takes the light fitting out of the car (it is a little cramped in there!).
I’ve heard lots of jokes about how many … it take to change a light bulb :wink:

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Had a similar problem with our 13 plate 3.75.
Found the only way to see what was going on was to use a mirror, also seem to remember that I couldn’t find any bulbs of the correct size and wattage(10amps) so had to order one from the main dealer.