Electrical Issues

[Riksta]

Hi Guys,

I'm hoping somebody could point me in the right direction here with some issues I'm having. I'll try to be as detailed as I can. The car is a 1999 NB8A, completely stock apart from a Pioneer Double-DIN head unit and unknown aftermarket immobiliser (which was in there when I bought the vehicle).

I've had a few issues with the electrics lately, what I originally believed to be a battery on its way out. The following things have all happened to me in the last month or so:

- One time, I started my car, started fine, I turned the headlights on and the car stalled, basically as if the drain of firing the lights took all the power away from the spark. Vehicle was in neutral at the time, so it was not me stalling it, and it was the moment I'd done the second click on the stalk to go from parkers to headlights.
- There have been three or four instances while driving the vehicle that the head unit has powered itself COMPLETELY off and then fired back up again within 1-2 seconds of powering off.
- Two mornings last week the car has taken a bit of time to crank over, almost as if the battery was dead. When it did fire, I noticed that all the presets in the stereo & the clock time were reset, as was my trip meter in the dashboard.
- Sometimes when driving and pulling up to traffic lights, once stopped the revs seem to drop almost to stall level and then raise up again like its having trouble sparking.
- While driving at night, along an unlit road or highway, while operating the electric windows its kind of noticable that the headlights dim a little, as do the dash lights.
- A couple of times at night when the car is at idle, it appears that the dash lights appear to be flickering a little in their brightness.

Now, as for what has been done recently to the car:

- It went in for a service about a month ago. At the service the spark plugs were replaced, I guess it must have been due for them as it wasn't something I'd asked about.
- At the service, when giving me the rundown before I paid for it, they advised that the battery had tested fine.
- Today, I took my car into Battery World and asked them to run a test, since after the service I did a road trip which consisted of about 5,000kms in 14 days. All the tests they did, including while starting the car, came back fine... in fact, they came back at levels higher than what they stated the normal levels should be. Due to this, they were hesitant in selling me a new battery as it may not solve anything, and advised the money could possibly be spent elsewhere on the car where the issue actually lies.
- The battery terminal connections are all on properly and tight and nothing seems loose there.

I know for a fact that the battery in the vehicle (which was in there when I purchased it) is not the "correct" type for the car, it sits a bit too high for the battery "hole" in the boot and you can tell that the clamp isn't quite on properly. It seems to have all the proper power for the car though, and not "underpowered" or anything, however the fact it isn't the right battery might have something to do with it (but the guy at Battery World wasn't 100% sure on this and advised due to the output its giving it should be fine).

My only other thought at this stage could be alternator. But then again, I really don't know enough to make the call and like with the battery, is it worth blowing the money on a new one when it may not solve the issues?

Any help, advice, or general info to point me in the right direction would be greatly appreciated right now!

Thanks for reading and apologies for the long post - I just wanted to give as much info as I could to help you guys troubleshoot.

Rik.

[hks_kansei]

Battery wise any car battery above the minimum cold crank amps will work fine.
MX5 battery issues re: type are more to do with the wrong type leaking, and causing fume buildup in the boot rather than a fault with hwo the car run.

For what you describe I would look at the alternator, have it tested by someone.

Another possibility is that the battery leads/clamps are stretched and not giving a good contact with the battery terminals.
I had this issue on my NB, which caused no starts, radio preset loss, and random issues.
I simply cut off the old terminal and put a new one on, problem solved. (for a simpler method wedge some thin metal in the terminal to pad it out and give it more grab)

[davekmoore]

Check all connections, especially earths.

[Roadrunner]

If the battery clamp isn't holding the battery down properly, it could be sliding around and earthing out a terminal to the bodywork.
This will cause all kinds of engine electrical issues.