Electrical problems? Clean your earth!

[MiseryStreak]

I was having electrical problems with my 2009 Mazda 6 2.2D Sport, the most recent of which was a red key symbol on the dash and car not starting properly. After lots of trawling through forums it seems like a common fault (along with quite a few others, mostly electrical).

We had a new battery fitted as it was tested and past its best. Mazda OE batteries are crap apparently and only last 3-5 years.

Anyway, my wife took it to Mazda and they wanted to change the whole instrument cluster and keyless module at a cost of around a grand inc. 3 hours labour. I told my wife I would see if I could fix it first. I read a post from a guy having similar problems who found the chassis earth point to be corroded. So I first cleaned up the main earthing point from the battery to by the suspension strut as it looked a little rusty. I went to start it to rule it out and no more warning symbols and it started perfectly. The boot now opens properly too.

After years of owning a 60s Lotus Elan and knowing full well the importance of poor earth connections it didn't occur to me to suspect a poor earth on a modern car.

Mazda have now also joined my long list of car manufacturers that I think are bds.

[paintman]

Corroded earth points & earth straps are very common - not just on older cars
The plastic covered earth straps have a habit of corroding to nothing underneath the covering so while the ends look OK there's nothing in the middle.
Quick check is to connect a jump lead from the battery earth terminal to a good clean metal point on the engine & see if it improves matters/cures the problem.

[t400ble]

Had same issue with a Fiat a few years back

Broken earth lead

[Morgaine]

Ah, just found this thread (I know it's old!). Having weird problems with my 2010 Mazda 6 Sport 2.2D. Car battery and key fob battery are pretty new, but it's pulling down the battery when sitting just a couple of days, ignition button is flashing red (though it does start off a jump pack) and it's started to take three or four times to do anything when hitting the Start button on occasion. Another owner's also suggested corroded earth strap, was just looking online to see where it goes to. Is it running to the wheel arch?

[paintman]

If you aren't fully recharging your battery with a battery charger after having to jump start it you're wasting your time as your alternator won't do much as far as recharging the flat battery is concerned & you aren't doing your alternator any favours either
https://www.optimabatteries.com/en-us/experience/2...

[Perseverant]

I had some problems with lights and indicators on our MX5. The main earth bits were fine but the problem was with the little earths for the light units which are like small bus bars inconveniently hidden under the headlight units - the earths unplug and the plastic unit unclips so you can clean the contacts - fiddly but worked.

[bristolracer]

I used to have a mini 1275gt that had a broken earth strap. It used to earth through the copper pipe that ran to the oil pressure gauge.
Took me a while to work out why there was always a big flash from the dashboard when I started it.

[Morgaine]

paintman said:

If you aren't fully recharging your battery with a battery charger after having to jump start it you're wasting your time as your alternator won't do much as far as recharging the flat battery is concerned & you aren't doing your alternator any favours either
https://www.optimabatteries.com/en-us/experience/2...

I've been fully recharging it every time since I knew it was going to happen.

It's now fixed. It was literally just corrosion on the thread of the bolt (negative battery terminal to chassis). You couldn't see this from the top, bolt looked mint. Bolt taken out, thread cleaned, bolt reinserted, problem gone away. That's a very bad earth point!