Weird electrical issues BH5 - Battery intermitently cutting out completely

[Flippymoi]

So I go to my car after work last night, disarm the immobilizer and go to start the car. Sometime between pressing my foot down on the clutch and trying to start the car, the car looses electrical power completely and the battery back-up siren starts to go. I open the bonnet, both battery terminals are tight and everything looks all good.

I get back into the car and somehow the power is back on, so I start her up and drive home.

On the way home, there were a few times where the revs dropped quite low, almost to a stall.

Today I am off driving to get a hair cut (not that you needed to know that) and on the way back my radio cuts out each time I press the brake pedal. Then about half way home the problem stopped and everything seems all good again.

Wtf is going on? Mechanical problems I can get my head around but electrical ones do my head in. If someone could help me here I would be so grateful!

The only changes I have done recently was remove and replace the ground cable on the battery to do some work.

[Swindog]

Aftermarket alarm?

[rex-leggy]

im thinking a bad earth somewhere . was it just the alarm or everything died?

[Swindog]

Yeah that's my thought too.

[Flippymoi]

Everything died. Interior lights went, and clock etc all reset. I checked the battery earth cable to the chassis and everywhere on the chassis is getting 12V at the moment.

What do you make of the power cutting out when the brake pedal is touched sometimes?

What else should I check for a bad earth?

[Swindog]

Your whole chassis is getting 12v? Everywhere?

If youve got 12v readings in places you shouldnt youll have a shorted wire touching something it shouldnt, like your chassis or a wire through the fire wall thats been cut maybe?

But id say a bad earth or youve hooked something up wrong.

[rex-leggy]

no thats the way it should be as the whole body should be a "negitive" .

whats important is the resistance of the earths are .

im sure i remember a similar issue not all that long ago . ended up being a shorted wire under the dash.

when the car is running check the voltage at the battery. it should go up from 12v to around 14v.

then you can rule out that the alternator isnt the problem.

also in the main fuse box there's a main fuse link (looks like a piece of wire with 2 spade terminals) check that as my wagon one that failed.

ill have a look for the old im sure it was a similar issue . i think it was CMPLSV car that had the issue

[reaperblitz]

-tighten all terminals on battery and all bolts that could have been moved in the process

-check the ignition wiring under dashboard..make sure there is a good connection and also that you havent taped (or it hasnt been) taped up to anything it could pull on.

-otherwise it could be microswitch for clutch that may be spliced?

[rex-leggy]

 reaperblitz said:

-otherwise it could be microswitch for clutch that may be spliced?

how would that kill power to the whole car.

another thing to check is the main feed to the alternator . mine cam loose and when driving along my car would randomly coast to a stop and then take off again

was a wtf moment for sure!

[reaperblitz]

It was more related to when he was starting his car. As I understood, some models use a micro switch which required the clutch to be pressed for it to be started.

Keeping in mind that I'm only running through options.

[rex-leggy]

oh gotcha like some autos you need to have the brake on as if the fact its in park isn't enough

[subieboy]

 rex-leggy said:

oh gotcha like some autos you need to have the brake on as if the fact its in park isn't enough

Double failsafe to avoid lawsuits...

[Flippymoi]

 reaperblitz']

It was more related to when he was starting his car. As I understood, some models use a micro switch which required the clutch to be pressed for it to be started.

Keeping in mind that I'm only running through options.

Yes, the clutch needs to be depressed to start, but this was not the problem as the interior lights, clock, everything was dead as well. I have also been having the electrics cut out while driving, although the engine keeps running.

I am getting 14volts from the alternator. Shouldn't all the power required to run the electronics in the car come from the alternator while the engine is on? What I mean is, once the car is started, you could remove the battery and the radio etc should still run? or is this not the case?

[quote name='rex-leggy said:

no thats the way it should be as the whole body should be a "negitive" .

whats important is the resistance of the earths are .

Rex-leggy, what should I be checking with the resistance of the earths? I have a multimeter but my skills extend to getting volt readings and that is about it.

Cheers

[rex-leggy]

 Flippymoi']

It was more related to when he was starting his car. As I understood, some models use a micro switch which required the clutch to be pressed for it to be started.

Keeping in mind that I'm only running through options.

Yes, the clutch needs to be depressed to start, but this was not the problem as the interior lights, clock, everything was dead as well. I have also been having the electrics cut out while driving, although the engine keeps running.

I am getting 14volts from the alternator. Shouldn't all the power required to run the electronics in the car come from the alternator while the engine is on? What I mean is, once the car is started, you could remove the battery and the radio etc should still run? or is this not the case?

[quote name='rex-leggy said:

no thats the way it should be as the whole body should be a "negitive" .

whats important is the resistance of the earths are .

/quote]

Rex-leggy, what should I be checking with the resistance of the earths? I have a multimeter but my skills extend to getting volt readings and that is about it.

Cheers

just disconnect grounds at both ends and measure the resistance of the cable between both ends .

ideally you want them to be 0 so a high a high resistance can cause electrical issues.