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There is a special sequence on the key.I knew someone who parked at Gatwick-left lights on and returned to flat battery-went to cark parkadmin. to phone for help.They said "just do this with the key" to get in and we'll come over with a battery.
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If all else fails consider removing the engine under tray and access the main power
You only need a pernament live, which you'll find in the boot on the boot light.
Take out the light fitting, disconnect the wires (separately if you can) then connect the charger +ve to the correct one. A continuity tester/multimeter will tell you which wire is earth (i.e. don't use that one, tape it up if possible), and the tailgate striker will suffice as a -ve connection point.
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I'm not sure shoving that much current down down the boot light cable is a good idea!
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Why not? It's only going to be 5-8A max if that. The circuit will likely be fused at 10A, and in any case the fuse will protect the wire from any damage.
In most electrical systems' designs current carrying capacity is not a problem. It's usually volt drop and protection device characteristics that determines the size of the cable.
Edited by mfarrow on 24/10/2008 at 14:15
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Brake light 21w
Indicator 21w
Tail light 5w
Fog lamp 21w
Backup light 21w
Light bulb (3rd brake light) 21w
Total watts = 21 + 21 + 5 + 21 +21 +21 = 110W
P= IV
I = P/V
I = 110 / 12volts = 9.167Amps
The scenario where all of those lights remain on simultenously would be slim, hence the fuse rating being close to the maximum possible current. I suspect BMW would have fitted cable rated to about 12-13Amps knowing the fuse blows at 10amps, +/- 10% tolerance on the cable current rating giving them a safety margin of 3 Amps.
I suspect the battery charger the original poster would be plugging in operates between 10-20Amps at least. I wouldn't want to risk putting that down a cable designed for a lighting circuit. Also, if the car was jump started through the boot light the current could surge in the 100's of Amps. This could cause a whole load more damage than a stuck door lock.
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Is the battery not mounted in the E36's boot, as it is on the E46 (98-05) model?
If so, and if I've understood correclty and the OP can get into the boot, the battery should be under a plastic cover between the right-hand wheel arch and light cluster. It undoes with two locking tabs that turn 1/4 turn each.
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Yes, depends when in 1998 the car was manufactured. It was in the Engine bay on cars built in the 1st half.
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to be honest, i've not noticed where the battery is on this one, its an R reg so probably early 98. ive had a few E36's (older than the current one) and the they had the battery in the engine bay, but couldnt say for this one. i'll check it out!
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dont the windows have to drop a bit on a coupe for the door to open?
Perhaps it wont open as a safety feature as power is needed to drop the glass.
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use the battery to boot light trick , this WILL give enough current to open the doors ,
just using apair of leads from another car will do it
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Pretty sure the battery on my E36 Coupe (323i) was under the back seat.
JS
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I suspect the battery charger the original poster would be plugging in operates between 10-20Amps
I've never seen that much coming from my 2 battery chargers, especially if just on the 'normal' setting.
I wouldn't want to risk putting that down a cable designed for a lighting circuit.
The fuse will blow before any damage is done. No electrical engineer worth his salt (or wanting to keep his job) would design a circuit with a cable not able to take the current rating of the fuse. A 0.5mm^2 thinwall cable is rated up to 13A.
Ultimately the protective device will always beat the cable to any damage. That's what they're for, to protect the circuit.
could surge in the 100's of Amps.
I never mentioned jump starting. Even so that's what fuses are for.
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Freddy, you are 'barking crazy'. If you use leads from another car then there is no current restriction and the battery is flat so it will attempt to draw a great deal of current. You have made seveal replies recently that would cuase damage to a vehicle so I suggest you consider your contributions very carefully in future. Regards Peter
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peter , i do not like you comment,
"You have made seveal replies recently that would cuase damage to a vehicle so I suggest you consider your contributions very carefully in future. Regards Peter"
if you have a flat battery on one car , why not start up the other car , and it will indeed put current into both the batteries ,
hell they used to sell a kit (admittedly with a diode) that you plugged into both cigar lighters , but that would be too easy would,nt it?
i indeed have a cigar plug/utility plug lead secreated away on my motorcycle , if i have a flat battery , then with the plug plugged into a passing car , i am started again,
now just to keep most people happy discussing the dia of cables ,, etc ,,
climb on the floor , find the starter motor , locate the large battery cable and connect your jump lead to it (if it makes you happy , use a spare battery) , then connect your earth lead , and open the door,
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Freddy 1, The battery is really flat so may be a couple of volts only, if you connect another car battery to the boot light terminal the flat battery will attempt to draw considerable current, may be initially 20 or 30 amps and this will wipe out the fuse or the wiring. Until the battery creeps up to about 7 or 8 volts on a restricted current charger the doors will not open. You could connect another battery but with 21 watt brake light bulb in series to limit the current then when the bulb brightness fades replace it with a head light bulb to speed up the charge but still limit the max current.
Were you not the person that suggested putting hydraulic fluid on a squealing fan belt. If drops of this flew off then it would react with the paint under the bonnet and blister it big time, another bad idea. If you have come here to learn then you are in the right place. Regards Peter
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>>No electrical engineer worth his salt (or wanting to keep his job) would design a >>circuit with a cable not able to take the current rating of the fuse. A 0.5mm^2 >>thinwall cable is rated up to 13A.
13a, that's exactly what I calculated to cope with a worse case scenario of all lights on, then to handle the fact that the cable manufacturers current rating will vary by +/-10% and then to give almost a 3A margin for unconsidered failures.
Consider the quanity of cars BMW assemble on a yearly basis and how many thousands of miles of cable they source, they will complete an FMEA (Failure Mode, Effect, Analysis) on each subsystem in the vehicle and assess the impact of failure. Based on the result they confirm the correct cable has been chosen and ensure they are not spending money unnecessarily on a higher rated cable.
BTW - your battery charger must take an incredibly long long time to charge if it doesn't go over 10Amps :-)
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As I said applying an regulated supply to the boot light, which is in fact on a different fuse than the the other lights, as it is a permanent feed on some cars, will blow the fuse due to the attempted inrush of current. One the fuse has blown then end of story as you can not now charge the battery, well not via the boot light. The side, brake, fog, reverse and indicators are nothing to do with this. Regards Peter
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As a contributor has suggested, does that mdel have the battery in the boot. ?? And can the OP open the boot with the key. Regards Peter
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And can the OP open the boot with the key.
Yes, OPs second post, which is why I suggested a charge from the boot light. I would sooner apply this method first than crawl under the car and attempt to connect to a completely unprotected circuit no doubt surrounded by earthed metal.
Aocal
Peter's right, the boot will be on a separate fuse, which is why even a botched attempt at charging will only blow the fuse itself, leaving the worst case only of the boot light not working. It will not damage the wiring, otherwise there'd be no point in fitting fuses would there?
Put it this way, if I were to put a bulb awkwardly in the light socket and accidently shorted the circuit out, I would immediately expect only the fuse to blow. I would not expect, except if there was fault in the wiring, the cable to go down and me to have to pull at trim and headlining to find it.
Also, there are plenty of horror stories on this forum where owners/friends/'friendly local garage' have fitted bigger and bigger fuses to a faulty circuit in order to 'fix' the problem. Luckily for them the only thing that happens is the bigger fuse blows and doesn't turn the car to cinders, thus underlining the robustness (though I wouldn't push it that far) of car circuitry.
Yes car manufacturers will complete FMEA analysis, but ultimately it's the electrical engineer who decides the fuse rating to go with a circuit.
My batteries charge fine and the car can even be started after only a few hours on a partially-discharged battery. 5 Amps is fine for an overnight charge.
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If he has boot access then the battery appears to be in the boot RHS under a cover. Regards Peter
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>>Yes car manufacturers will complete FMEA analysis, but ultimately it's the electrical >>engineer who decides the fuse rating to go with a circuit.
Blimey, which Research & Development establishment do you work at?
A fuse rating, wire rating any rating on anything in the car or any other product for that matter will go through many processes before being approved and accepted. FMEA being just one.
It is not solely the electrical engineers decision, I know for a fact that BMW work to 6 sigma's so there's just one more process to force decision making.
One man doesn't make a decision, everything is forced through a design process.
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thanks all for your input, however the discussions on fuse ratings and wiring have gone totally over my head!! i checked in the boot and the battery is not there, so thought i'd give the key another chance. held the key to the left for so many seconds and then swiftly turned it back the other way as someone had suggested
this did the trick and i am in, got the bonnet open and jumped it so all sorted now
Edited by BeemerCoupe on 01/12/2008 at 11:41
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