Urgent electrical help needed
Discussion
Strange one this. The E39 suddenly wouldn't start the other day, the starter just clicked. Fired first time on a jump start and got me back home then wouldn't start again when I got her on the drive. Simple, dead battery as she will drive on alternator output alone. Replaced the battery and all was well for a couple of days.
This morning the car went into limp mode on the way home and various electrical systems were switching on and off. ABS, TC and airbag lights came on and went off randomly and the auto box wouldn't change. Radio was switching on and off all by itself. Got on the drive and the starter just clicked again.
Checked I'd tightened the battery terminals, all good. Checked the engine earth, still nice and tight.
I've never had the charge light come on (assuming it has one)
There was a feint electrical smell in the engine bay the other day but its gone now, I put that down to the alternator trying to put current into a high resistance battery although I could have got that wrong!
What could it be? I've assumed the alternator is good as it got me home on its output and they're big bucks to replace so I don't want to change it on a whim...
This morning the car went into limp mode on the way home and various electrical systems were switching on and off. ABS, TC and airbag lights came on and went off randomly and the auto box wouldn't change. Radio was switching on and off all by itself. Got on the drive and the starter just clicked again.
Checked I'd tightened the battery terminals, all good. Checked the engine earth, still nice and tight.
I've never had the charge light come on (assuming it has one)
There was a feint electrical smell in the engine bay the other day but its gone now, I put that down to the alternator trying to put current into a high resistance battery although I could have got that wrong!
What could it be? I've assumed the alternator is good as it got me home on its output and they're big bucks to replace so I don't want to change it on a whim...
It won't run on alternator alone; the alt needs some power from the battery for the exciter coils. (With a dynamo you can take the battery off and it will keep running)
Where did the battery come from? WHen I buy a battery I get it from a decent motor factor who have a clever volt meter that will tell you in 2 minutes if it's the battery or alt so you don[t have to guess and replace the alt and then find it's OK.
Is the belt tight enough?
Where did the battery come from? WHen I buy a battery I get it from a decent motor factor who have a clever volt meter that will tell you in 2 minutes if it's the battery or alt so you don[t have to guess and replace the alt and then find it's OK.
Is the belt tight enough?
Belts all tight and running the cooling etc. Battery is from GSF and was showing 11.6 v when connected to the car when I got her home this morning.
Currently on charge while I ponder the problem.
Once she is going again I can measure voltage and would expect it to rise as the RPM increases, but that's a few hours away.
If alternator output was suspect I would expect to see a charge light of some sort display?
Currently on charge while I ponder the problem.
Once she is going again I can measure voltage and would expect it to rise as the RPM increases, but that's a few hours away.
If alternator output was suspect I would expect to see a charge light of some sort display?
RP1 said:
If you've got weird electrical issues on an E39, the ignition switch is a common culprit. I would bet that it's the cause of your woes. Certainly caused a lot of inexplicable things to happen on my old one!
Interesting... Can you take the block connector off and fudge it like in the old days of hot wiring?From another thread...
scott10005 said:
Hi,pretty sure your fault is with the ignition switch (the electrical part on the back of the ignition barrel) they are prone to the electrical contacts burning out and creating a bad contact,all the faults you have described are consistent with the terminal "R" going missing,everything terminal "R" powered not working ie,radio,the airbag control unit (fault stored in unit will point to a missing "R" feed),also gearbox control unit unit and multi function steering wheel have the same feed going to them. You can confirm this fault by removing the column cover form behind the wheel and wiggling (technical term) the switch part when the fault occurs,you can also monitor the thick violet/white wire,when the fault is there you will only get about 1-8volts instead of 12v.
Hope this helps,
Scott
I'd say we've got the first thing to eliminate. Certainly cheaper than an alternator and describes most of my symptoms...Hope this helps,
Scott
They are on ebay 2nd hand around £15 and its very easy to change. That's the easiest option.
Its a fairly simple device, considering all it controls - You can repair/recondition it - Inside the switch there are various contacts along a shaft which make contact with various point - these can spark and burn/scar the surface over time causing bad or non existant connections. You can sand them down and make them better, in my experience it only improved the issue rather than cured it, but it depends on how good a job you do and how badly they are damaged!
It's easy enough to take apart and do this - plenty of info out there on BMW 5 forums and such. Give it a try and if it doesn't cure it, you'll have at least elimintaed something! 99% sure it will sort or improve things though!
Your battery should ideally read around 12v with the car off, car running and charging from the alternator you should see around 14v.
ETA - beaten to it!
Its a fairly simple device, considering all it controls - You can repair/recondition it - Inside the switch there are various contacts along a shaft which make contact with various point - these can spark and burn/scar the surface over time causing bad or non existant connections. You can sand them down and make them better, in my experience it only improved the issue rather than cured it, but it depends on how good a job you do and how badly they are damaged!
It's easy enough to take apart and do this - plenty of info out there on BMW 5 forums and such. Give it a try and if it doesn't cure it, you'll have at least elimintaed something! 99% sure it will sort or improve things though!
Your battery should ideally read around 12v with the car off, car running and charging from the alternator you should see around 14v.
ETA - beaten to it!
Edited by RP1 on Friday 7th December 10:22
BliarOut said:
Battery is from GSF and was showing 11.6 v when connected to the car when I got her home this morning...
If alternator output was suspect I would expect to see a charge light of some sort display?
Alternator is goosed. Charge light is only an indication that something may be wrong, no light does not (unfortunately) mean that everything is OK.If alternator output was suspect I would expect to see a charge light of some sort display?
Start the engine and put a voltmeter across the battery. You should have 14.2-14.5v after a very short while. Anything less points to lack of charge from the alternator.
chazola said:
If you test it and get no charge, I'm guessing voltage regulator if you've got high-ish miles, if it's a Bosch it should just unscrew out and new one slot in.
Yes, if the ignition switch proves to be OK my next port of call would be the regulator, if the car has big miles the brushes could be worn down. My last one went out to lunch at around 160k. Tenner from a auto factor 
john2443 said:
It won't run on alternator alone; the alt needs some power from the battery for the exciter coils. (With a dynamo you can take the battery off and it will keep running)
Where did the battery come from? WHen I buy a battery I get it from a decent motor factor who have a clever volt meter that will tell you in 2 minutes if it's the battery or alt so you don[t have to guess and replace the alt and then find it's OK.
Is the belt tight enough?
At this actual moment I have a 2006 s type diesel running in the workshop with no battery fitted,it has been so since 9 this morning,it will drive,all the lights are on on the dash but it definitely is running from the alternator alone.Where did the battery come from? WHen I buy a battery I get it from a decent motor factor who have a clever volt meter that will tell you in 2 minutes if it's the battery or alt so you don[t have to guess and replace the alt and then find it's OK.
Is the belt tight enough?
Not to mention the many times when without jump leads using the practice of taking the battery from a running car and putting it on a car with a dead battery to get the dead car started,
leaving the running car without a battery.
shoehorn said:
john2443 said:
It won't run on alternator alone; the alt needs some power from the battery for the exciter coils. (With a dynamo you can take the battery off and it will keep running)
Where did the battery come from? WHen I buy a battery I get it from a decent motor factor who have a clever volt meter that will tell you in 2 minutes if it's the battery or alt so you don[t have to guess and replace the alt and then find it's OK.
Is the belt tight enough?
At this actual moment I have a 2006 s type diesel running in the workshop with no battery fitted,it has been so since 9 this morning,it will drive,all the lights are on on the dash but it definitely is running from the alternator alone.Where did the battery come from? WHen I buy a battery I get it from a decent motor factor who have a clever volt meter that will tell you in 2 minutes if it's the battery or alt so you don[t have to guess and replace the alt and then find it's OK.
Is the belt tight enough?
Not to mention the many times when without jump leads using the practice of taking the battery from a running car and putting it on a car with a dead battery to get the dead car started,
leaving the running car without a battery.
Well I've just been out and rebuilt the ignition switch. Sure enough the first pair of contacts were looking a bit burnt. Dressed them up with a points file and refitted and she fired up first time. Can't be 100% certain as she's had a morning on charge but the symptoms sure fit with the ignition switch playing up.
Thanks for the pointer, I'd never have suspected that
Thanks for the pointer, I'd never have suspected that
BliarOut said:
Well I've just been out and rebuilt the ignition switch. Sure enough the first pair of contacts were looking a bit burnt. Dressed them up with a points file and refitted and she fired up first time. Can't be 100% certain as she's had a morning on charge but the symptoms sure fit with the ignition switch playing up.
Thanks for the pointer, I'd never have suspected that
10 bob still says your alternator is goosed. Have you measured the running voltage yet?Thanks for the pointer, I'd never have suspected that
You can thank me later.
Don't think so. The alternator wouldn't trip limp mode, bring on the ABS and TC lights, switch the radio on and off at random, disable shift on the auto box and yet fail to trigger the charge light.
A failing ignition switch on an E39 produces all those symptoms
I'll quite happily take your ten bob in a few days or when I've got a second pair of hands to operate my multimeter...
A failing ignition switch on an E39 produces all those symptoms
I'll quite happily take your ten bob in a few days or when I've got a second pair of hands to operate my multimeter...
BliarOut said:
Don't think so. The alternator wouldn't trip limp mode, bring on the ABS and TC lights, switch the radio on and off at random, disable shift on the auto box and yet fail to trigger the charge light.
Sorry - but yes it would. Any falling voltage would trigger any or all of those symptoms. It did on my E46 last year.BliarOut said:
I'll quite happily take your ten bob in a few days or when I've got a second pair of hands to operate my multimeter...
It's sitting waiting for you. Silence after a few days will signify that I was correct... (You don't need a second pair of hands, BTW, just start the engine and put the multimeter across the battery and tell us what the reading is.)
Dr Doofenshmirtz said:
Alternators need an initial ~12v on the exciter coil from a battery, then they'll continue to produce power without a battery. However, the battery will help to smooth out the voltage from the alternator (they act like a big capacitor). So running without any battery is not advisable.
Yes,obviously you would need a battery or in my case a booster pack just to start it but it WILL run without a battery or booster pack,which is what the original statement implied.Gassing Station | General Gassing | Top of Page | What's New | My Stuff