NB8B - Key turn doesn't start car but battery is fine

[mmxx55]

Hi All,

I ran across an odd problem this morning and I'm hoping to pick someones brain out here for some support .
Thanks in advance to everyone who reads this.

Car:
- 2001 NB8B with AU Mazda Factory Alarm (I think it is a dealer fit option).
- Battery replaced ~ 4 months ago.
- Alarm is currently disabled from engine bay.

Symptom:
- Remote central locking does not work. Key lock does not appear to engage central locking.
- With key in ignition, there are no dash lights (not even with key in accessory). I didn’t try headlights, but I think battery is fine.
- Car battery is strong (4 months old, reading 12.9V in the morning). Checked with a spare jump start battery with no effect.
- Car alarm has been disabled, however when I turned the siren unit in the engine bay to TEST, the siren sounds very weak.

At the moment, I’m thinking potentially:
- Keyless entry remote battery has died. However, it doesn’t explain why central locking etc. doesn’t work with the key unless they are wired together.
- Alarm backup battery has died.
- Immobiliser issues with the car.

Has anyone experienced something like this before?

Cheers
Kevin

[StanTheMan]

check you battery to make sure both positive & negative or on tight & are not covered in that green sh*t.

[Okibi]

If the battery seems strong, but everything thing else indicates it has a cell fallen over, then adding on the 2nd battery should have started the car or did you just swap the batteries over?

If you did that, perhaps it's something as simple as the battery clamps being covered in lots of corrosion and not being tight enough to make a decent connection? Also check the negative lead at the body to make sure it's well attached etc.

(Sounds a little too simplistic to be it, but it's a start).

[mmxx55]

If the battery seems strong, but everything thing else indicates it has a cell fallen over, then adding on the 2nd battery should have started the car or did you just swap the batteries over?

If you did that, perhaps it's something as simple as the battery clamps being covered in lots of corrosion and not being tight enough to make a decent connection? Also check the negative lead at the body to make sure it's well attached etc.

(Sounds a little too simplistic to be it, but it's a start).

I'll double check but my concern leans towards the immobiliser preventing the car from starting.
I bridged a second battery on using jump-starters & tried to start the car, without success (no lights etc.)

check you battery to make sure both positive & negative or on tight & are not covered in that green sh*t.

Terminals are clean, but I'll double check tonight.

Cheers for the help guys,
A few items to check tonight but I'll knock them off 1 by 1.

[Nevyn72]

Might seem a bit obvious but have you checked the main fuse (100A) in the engine bay?

[green_comet]

Check your earth connection from the battery to the body. Make sure it's making a good clean connection with the body.

Sent from my Nexus 5 using Tapatalk

[Mr Morlock]

my punt is that it has nothing to do with the battery and far more likely to do with the added pest of an immobiliser- these things seem far more trouble than they are worth. If the internal light or headlights etc work then rule out battery. If you are in RACV or similar you can get a call out and take it from there. You can also ring- talk to a tech who is full bottle on alarms fitting and that also means de installing. You can also get a car put on the flat top - pay out of your pocket or free on NRMA RACV etc just tee it up with an auto elect or specialist before hand. With your descrip a techo may be able to advise no cost.

[mmxx55]

Hi all,

Have finally diagnosed it all. Unfortunately not as interesting as I thought. One of the terminals on the battery was slightly loose (and by slightly I meant I couldn't move it with my hand, but I got about 3 turns on the terminal threads).

I undid it and cleaned up the terminals so hopefully it's all good now.
I almost thought I had 2 flat batteries in the space of 4 months. That would've been ridiculous.
Thanks for all the tips.

Cheers
Kevin

[green_comet]

Nice work, you always check the basics first. Once you rule them out, then you start calling people.

[Okibi]

STM

[mmxx55]

Nice work, you always check the basics first. Once you rule them out, then you start calling people.

Indeed. I had about 2 minutes to try and get the car started before having to jump start the other car, get it to a Kmart and grab a new battery for that car. Hence, I didn't have the time to do a proper fault diagnosis.

I hope this becomes a good thread in future for others who experience electrical issues.

[Mr Morlock]

Good for sure. If it was a battery connection it should have affected lights or horn- you would have thought.

[Guran]

If the battery was dead flat, then yes it would affect lights and horn, etc as these don't draw much current. I recently had trouble starting my NC. The lights, horn, radio, etc were working fine, yet turning the key resulted in nothing more than "click click click". Jumper leads onto one of our other cars got the NC started first time. The issue was a drained battery caused by a full day of listening to the radio while detailing the car. The starter motor just needed more juice than the drained battery was able to deliver.

[Okibi]

This can be made worse by a cold engine and battery.

[bruce]

Some nice hot water on the terminals to dissolve any crud (hard to do in the boot), maybe a very light sand on terminals and clamps, a smudge of vaseline (prevent crud forming) and tighten.