Total loss of electrical power on start-up?

S

sixspeed

Senior member
 Surrey, UK
Just went to use the car tonight, and literally the split second I turned the key from the ACC position to the starter position, everything went dead. No dash lights, no interior lights, boot solenoid not working, even the dash needles are still in their "active" position.

I presume a fuse has blown somewhere - but anyone any tips as to where I could look? I didn't have time to start looking around now. Had to get the S4 out, and attach jump cables to the terminals under the bonnet to activate the boot solenoid so I could get my bags out, and then used the Audi for the journey instead.

Will take a look tomorrow, but just wanted some obvious places to start. Since it seems to be a total loss of electrics from the battery I'm guessing maybe there is a master fuse for the battery itself? I did change the battery at the weekend as the old one had been dying on me, and was struggling to hold a charge. However, I used the car for a good day or so after the swap, and it was fine... until now.
 
I would check the batt connections as a starting point. Sounds like a dodgy ground to me, that could be at the battery, starter, poss even alternator. More likely the battery though as too much of a coincidence that you've just changed it and now its dead.

I had the exact same issue on my Land Rover, which was a lot easier as there is barely any electrics not like a Zed! But that was a dodgy alternator.
 
gallaghb said:
I would check the batt connections as a starting point. Sounds like a dodgy ground to me, that could be at the battery, starter, poss even alternator. More likely the battery though as too much of a coincidence that you've just changed it and now its dead.

I had the exact same issue on my Land Rover, which was a lot easier as there is barely any electrics not like a Zed! But that was a dodgy alternator.
Click to expand...

Agree - take both battery connections off and refit them. Seems too much of a co-incidence to be anything other than that, or a duff battery fitted.
 
Yeah, battery connections will be the first point of call. Just seems odd that it was fine all day Sunday (took it to Goodwood and back etc), and then all the electrics came on fine with the ignition on, then just died completely when I went to turn the engine over.

That's why it feels like a fuse to me - it was like the current draw for the starter motor blew something.
 
I can offer one explanation is that you fitted it and all was well. Driving takes little current so no issue evn if loose. 2 days later you fire it up cold and the current draw is way higher and thus the loose connection shows itself.

Of course if not then elimination. Is the battery charged? Can you get a reading on the front jump start battery points, etc.?
 
Was it one of the BMW AGM batteries or an aftermarket one?

Doesn't it require a 'battery reset' too?
 
Mine did require a "battery registration" with the car's ECU. The air-con and some other electrics didn't work after the new battery and only when my mechanic did the battery registration thing (Used an Autologic car diagnostic) was it fixed. Perhaps that? :?
 
Full points to those that suggested a dodgy earth. Sure enough, the earth terminal on the battery was loose.

However, having tried to tighten it up, it just doesnt seem to hold very solid. Aside from replacing the battery clamps, any ideas? I'm guessing the new Bosch battery (I wasn't up to paying 3 times the price for a BMW one) has ever so slightly narrower posts than the old OEM one.
 
Hmm not sure what you could do to get a better connection. But if you go down the route of a new clamp I can recommend these guys :thumbsup:

http://www.vehicle-wiring-products.eu/VWP-onlinestore/home/homepage.php
 
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