2003 MX5 NB Strange Electrical Issue: Side Indicators Permanently On No other Dashboard lights on

Technical Area Electrics & ICE
1
  1. My model of MX-5 is: 2003 MX5 2.5NB
  2. I’m based near: Sandhurst Berkshire
  3. I’m looking for technical help or recommendations on:
    First up I am not a mechanical person I tend to leave it to the experts.

We had the car restored by the great team at the MX-5 Restorer who did an excellent job on the body work and other parts (waterpump etc).
Unfortunately we left as USB charger plugged in over winter and flattened the battery. I boosted the MX5 with a NOCO Boost Sport and she started but the Hazard warning lights where constantly flashing she started on about the third time. We drove her up and down the street few times to try and get some charge in. Normally I think this is some kind of immobiliser/alarm but not sure.

We then switched her off to try and see if the hazards would go out, a buzzing sound (bit like an alarm) sounded in the engine bay then faded away. Trying not to go the boost route again (and cause damage) I purchased a new battery (Euro parts plugged in the Reg code to ensure we got the right one).

When i attach the battery the indicator lights (left/right) are solid no hazard flashing, and are on solid in the dashboard (left right indicator lights) no other lights are on in the dashboard. Turning ignition does not work (turning the key in the ignition does nothing) no dashboard lights up etc she is effectivley dead except for the left right indicator being illuminated both outside and on the dashboard.

I disconnected the battery and left her alone I didn’t want to cause her any damage if she has shorted etc.

We are her second owners no aftermarket alarms/immobilisers fitted etc.

I am thinking:
1/Fuse blown during boost or connecting new battery. I followed instructions here and put Red Terminal on + then - on, when boosted she started as normal (Except flashing lights) and drove normally so it did not seem to damage the wiring then.

2/It might be an immobiliser setting, based on the hazards flashing as we drove her around. How do I reset this?Is it attach battery then turn key in the door to reset? For additional detail the door was unlocked when we switched her off so she hasn’t locked again, this might be the issue and simple.

Any help would be gratefully received she has a lot of memories in her hence we got her restored and she was running amazingly well afterwards (Full compliments to gareth and team).

Thanks
Dave

2

Might sound obvious but you have connected the new battery the correct way round haven’t you?

3

Thank you.

Feel like such an idiot.

I thought batteries all went in the same way in the box as standard. Oh no the one I took out was left to right facing towards the spare tyre. This one facing the spare tyre is Positive right negative left, why do they do that?. So I reversed the polarity…

Ok so the light is off now.
I turn the key its not firing up. The hazard light is going I suspect I blown a fuse I hope otherwise it is going to get expensive.

Dave

4

So either the wrong battery was fitted previously or the Euro Parts reg number thing has done you over or the battery has been fitted back to front. I too hope it’s a blown fuse somewhere…

image
image3024×4032 2.81 MB

To confirm, the positive terminal should be the one covered by the red cover it that photo.

5

Yeah.
So now following this thread:
Car will not start or even turn over, nothing after lay up, new battery but no dash lights showing p - Technical Area / Engine, Transmission, Exhaust etc - MX-5 Owners Club Forum (mx5oc.co.uk)

Pulled the 100AMP fuse smells like its blown shining a light in it I can see right through to blue at the bottom ie no connector.

I think its one of these from Euro Parts
Male PAL Fuse 100amp Single | Euro Car Parts

Its what comes up when I put the reg num in.

6

Did you not have to unbolt that fuse to remove it? And I would have expected it to be a black fuse.

7

Hi,
Yes unbolted the fuse box two bolts, one left one right undone pulled out its the fusebox under the bonnet.
Fuse is below

20240409_195046
20240409_1950461500×2000 226 KB

8

Well, you’re doing well for “not a mechanical person”. That fuse is certainly blown, I hope that’s the only damage.

9

Hi Robbie,
Thank you so much.

It was easy I had a little socket set (I build my own computers) so it was two bolts on the fuse box two bolts on the fuse so that was simple I read up first which is why I was annoyed about the battery that was schoolboy error.

Dave

10

Hi
Just an update 100AMP fuse fitted, car is back online three minor problems.

1/Engine fault light is now on.
2/Radio doesn’t work now probably fuse.
3/Speedometer cable intermittent fault (goes up and down like a flag waving sometimes).

So she’s off to the garage.

Thanks again for the support :slight_smile:

Dave