Mazda MX5 NC Dead as a Dodo please read me

[APJMX5]

Hello my first post so please be kind, I’ve had my dark blue NC for almost 2 years and it’s be very reliable until last Saturday.

The car is almost completely dead only parts of the car now working is the central locking, interior light, red doors open symbol and flashing led for the alarm. Sometimes the lcd with mileage works and sometimes the red led for the ignition led lights up. So no way to start it or turn anything else on.

RAC came out today confirmed the above and said they couldn’t help.

The battery is perfectly fine, there Power at the main fuse box under the bonnet with no fuses blown. The interior passenger footwell fuse box is only live to the bottom set of fuses but the top set have no feed and are dead.

Any thoughts at all please?

PS I have searched forums already and can’t see a similar issue or way to resolve it. RAC suggested taking it to a main dealer to fix btw.

Thank you so much Andrew

[mike9009]

No direct experience of the issues you have, but it feels like an earthing issue, immobilizer issue or an ECU issue to take out so many things.

Does the car start?

[RazerSauber]

As above, sounds like an earth fault. Check the connection between battery and body.

[APJMX5]

Thanks both it is very strange how a couple things work and not all.

No engine won’t turn over on starter but haven’t found of roll starting the car as I can’t move the car up my drive.

[APJMX5]

Battery connections all good and power to fuse box just strange it happened out of the blue.

[Thats What She Said]

Check for water ingress, damp carpets, blocked drains etc. Maybe some water got into the ecu or fuses box.

[APJMX5]

Thank you

[anonymous-user]

I had a similar issue with my Ford Connect van, would randomly not want to play. I eventually tracked it down to a poor battery earth connection AND a poor positive connection....cleaning both up and a smear of Vasaline seems to have cured it, so far.

[rovermorris999]

As well as all the above, disconnect the battery and leave it for half an hour so everything discharges. Clean the connections and try again. Squirrely voltages may have put the ecu in a huff (these are technical terms) so worth a try.

[ian_c_uk]

I'd recommend signing up to forum.mx5oc.co.uk, even if not (yet) a member, you can sign up and ask for help.

I don't have a Mk3 at present but someone may have come across similar before.

[speedking31]

APJMX5 said:

Battery connections all good and power to fuse box just strange it happened out of the blue.

Have you checked the remote end, earth connection to the vehicle body? Have you tried connecting up another car, as if doing a jump start, and see if yours works off its power?

[APJMX5]

Thanks I have asked the same question on a MX forum.

I have now tried 3 batteries all fully charged so as the RAC guy said the breakdown is after the main fuse box which is live.

[speedking31]

But no matter how well charged the battery, if the earth/ground isn't well connected to the body then various electrical components won't have a good return path to the battery and so won't work.

e.g. does the horn work? If not then run a wire directly from the earth terminal of the horn to the battery earth terminal. Does it work now?