Electrical problem

[Status]

Hi got a problem with my m coupe so here goes
Gone out to start it for first time in about 5 weeks,nothing ,no electric ect ect ect so try and charge battery up but wouldn’t have it battery was replaced ln july with another Bosche,AA man has come round to replace wot I thought was battery,He said it’s not the battery it seems like a main fuse as there was 9 volts in battery which should be enough to start car,done a few tests and it seems as if there is nothing from the fuse box situated next to battery ,got power from battery to box then nothing,fuses seem ok,
Any suggestions
Checked the usual stuff
Tia

[davidmudley12]

9v sounds incredibly low to start the engine, it should be up above 12v.

Given the number of electrical problems I’ve hear and read about all roads start with charging / replacing the battery. It’s quite special the wide range of problems that come back to a poor battery. Also worth checking the earth if there is nothing.

Good luck.

[Status]

Yeah but if I had just nine bolts I would still get the hazards to work and something on the dash,I’ve got no electrics at all

[flyingscotty]

I'd say it was battery low voltage as well, normally it's at 14.4 or thereabouts, the Z will not turn over or anything when it dips below a certain voltage to protect car. I'd also check and make sure battery connections are tight this can also cause a problem far greater than you'd imagine. Halfords sell an amazing and pretty small jump battery which is good up to 4.0 litre car for around £100, it's so small it can fit in a jacket pocket. I'd get one and try and see if that works, if it does then put your battery on a trickle charge and get it back up to full

[Raj_UK]

I’m no expert, but if after charging it still only measures 9v surely that is a knackered battery? Whether that is the reason the car won’t start I couldn’t tell you....

[Status]

That’s wot I thought Raj so I’m going to take the battery off my Impreza tomoz and try that as for paying out £100 quid ,I’d think about that if it wasn’t under warranty but if I had 9 volts I would still get the ignition lights come up when I turn the key wouldn’t Im not getting nothing.main fuse a possibility ?all connections correct and clean

[ph001]

9v won’t do sh#t. As soon as you try to take any power out of it, the voltage will drop to almost nothing. I’m surprised at your AA man’s advice.

[craig3.2]

Hi got a problem with my m coupe so here goes
Gone out to start it for first time in about 5 weeks,nothing ,no electric ect ect ect so try and charge battery up but wouldn’t have it battery was replaced ln july with another Bosche,AA man has come round to replace wot I thought was battery,He said it’s not the battery it seems like a main fuse as there was 9 volts in battery which should be enough to start car,done a few tests and it seems as if there is nothing from the fuse box situated next to battery ,got power from battery to box then nothing,fuses seem ok,
Any suggestions
Checked the usual stuff
Tia

Too low voltage as said,should be around 11-4.4v.

Put it on a c Tek charger,on the AGM battery setting, overnight, approx 8 hours if memory serves me,from doing mine last year,and after that all should be good.
I thought my battery was toast,bit thanks to the c Tek charger(bought for around £60) it was fine..... cheaper than a new original BMW battery or similar,and can be used again in future if needed.
Hopefully that will sort it.
Check Euro carparts or other online sellers as often deals on..... mine was the £100+ model,got with over 40% off.

[Status]

Yeah Craig I’ve had it on the c tek charge,I’ll try the agm setting which I nearly did from the start ,should’ve followed my instinct maybe and yes ph I thought the same,only thing is I’ve got power from the battery but then nothing going from the fuse box next to the battery,is that normal

[ph001]

Yeah Craig I’ve had it on the c tek charge,I’ll try the agm setting which I nearly did from the start ,should’ve followed my instinct maybe and yes ph I thought the same,only thing is I’ve got power from the battery but then nothing going from the fuse box next to the battery,is that normal

Depends where you are measuring on the fusebox...many of the fuses are switched with the ignition. Have you tried measuring the voltage at the jump point under the bonnet? That should measure about the same as what you are seeing across your battery.

Even if you can get some charge into it with a good charger, that battery will never get anywhere near back to it’s original capacity after being left at 9V. The capacity is the Ah (amp hours) rating. E.g a 100Ah means the battery can supply 1A for 100hours before it goes flat. So even though you may be able to recover it to 12.6V again it will have bugger all Ah.

This confuses a lot of people because they measure 12v and think the battery is good when that is far from the truth.

Even letting the battery get down to 11.0v for 24hrs causes quite severe sulphation on the plates meaning you will lose about half the capacity. It’s very hard to recover batteries from this despite what battery charger manufacturers would have you believe.

[Argyll Andy]

Does the E85/86 have the hidden menu option, like my 2006 3 series to see the resting voltage?

Mine wouldn’t start, stuck it on the charger overnight and did start. Tried again shortly after nothing, no ignition lights interior lights. Just enough power to access the secret menu showing 10.8v but wouldn’t do anything, turnover, indicators, interior lights etc, nothing. Phoned a mechanic mate, told him the standing voltage and he said that’d do nothing battery was fecked at 10.8V so I’m surprised the AA guy said 9V is enough when 10.8 would do nothing. To be fair to the car this was in December and the battery was still the original 2006 BMW one.

As someone has mentioned being that low it might not even be switching a relay/module to allow any power to go anywhere from the fuse box but well out of my knowledge base.

Hope you get it sorted

[Mr Tidy]

Does the E85/86 have the hidden menu option, like my 2006 3 series to see the resting voltage?

I'm pretty sure E85/6s don't have that feature.

As the tax on my M was expiring on 31 December, given time of year and lockdown I thought I'd SORN it but as it lives outdoors I've no charging option sadly. It soon became apparent the solar charger I had tried didn't do anything!

Anyway I last used it 24 December (didn't get a run after Christmas because weather wasn't that good). Then this month I realised I didn't want it to be an ornament so I taxed it. Went to use it on 5 Feb - the key managed to open it, but turning the key in the ignition made all the dash lights go out and set the alarm off!

Luckily I had my £60 Amazon starter pack handy just in case and that fired it up no problem and silenced the alarm, so I took it for an essential journey! Then we got snow, ice and gritted roads so I didn't try again until Saturday (13th). I had the starter pack handy, but it fired up OK - I'm just hoping the battery isn't totally kn*ckered. But I didn't think to check the voltage on the jump-start points under the bonnet - will try to do that next time I'm out.

But I hope you find a solution Status. :thumbup:

[Status]

Makes sense regarding the battery I’ll take the battery off my Impreza which is fully charged and take it from there
Regarding the reading from under the bonnet,was getting nothing also the battery pack both mine and the AA mans didn’t do anything

[Status]

Just put the fully charged battery from my Impreza on and nothing,no electrics wot so ever,looks like a fuse possibly ie main fuse ? Don’t know where that is,bloody electrics,give me a cortina any day ha ha,looks like an auto electrician is on the cards,anyone know any Bishops stortford area ?

[ph001]

I can't imagine you have blown the main fuse - it's something like 250A, but I guess it's something you can check. It's part 4 in this diagram but unfortunately I'm not exactly sure where it located....

Z4 main fuse.jpg (84.42 KiB) Viewed 425 times

There are also several other large fuses under a cover in the main fusebox behind the glovebox....

Z4 fusebox.jpg (49.96 KiB) Viewed 425 times

...and also some more under the bonnet on the passenger side....

Z4 under bonnet fuses.jpg (141.01 KiB) Viewed 425 times

BUT I'd really be quite surprised if they had blown since you haven't really shorted anything out to speak of. Before you do anything it is worth disconnecting the battery one more time and shorting the +ve and -ve battery leads together for 30secs or so. Then reconnect.