[gaz123d]

Hi Guys I'm new to the forum looking for some advice. I bought a bmw 123d 6 months ago and its been great until a few days ago. I went to start the car and just get one click noise from the starter.
We tested the battery and it was ok but replaced it anyway for a new one.The car would start fine from the jumper points under the bonnet but not off the main battery in boot.
Got under the car to find the two red cables that lead under the car from the positive terminal had been rubbing on the chassis and the main thick cable melted the insulation and earthing to the cars body..... Dangerous.
I have insulated the cables for now and cleaned connections and priced new cables but still not starting.. confused and no idea what i can do now. Any help would be so appreciated Thanks again....Gaz

 

[Octavius]

Look at the big red terminal block on the positive terminal of the battery. In there is a safety fuse and that will have blown when the cables shorted to earth.

 

[Octavius]

61146971370
Power distribution box with fuse

 

[Octavius]

eBay item 391342932254

 

[gaz123d]

Hi mate thanks for help. We have tested across the fuses on the battery and they all were OK. Lights heaters everything else works etc. I'm stuck now???

 

[0l0dom0l0]

Hi mate thanks for help. We have tested across the fuses on the battery and they all were OK. Lights heaters everything else works etc. I'm stuck now???

Replace the cables first and try again if it's starting from jump leads under the bonnet.

 

[gaz123d]

Car starts fine from jump points under the bonnet.Have constant 12v at the starter motor until i try to start then drops to zero.Think I need to bite the bullet and get it towed into BMW. Thanks for the input and help guys.

 

[ste815l]

Have you got 12v at the jump starting point under bonnet? If so check to see if this is dropping to zero when you crank car.

 

[gaz123d]

Hi Ste, have 12v at the jumper point then get voltage drop when cranking. Would this suggest its that BST?

Thanks again mate

 

[Octavius]

Sounds like the damaged cables cannot handle the power required to power the starter. If you have a long enough jump lead, run it from the battery to the positive post under the bonnet to prove it.

 

[gaz123d]

Hi thanks for the input, Have just been out and tried what you said with the jump leads and car starts, also tried it from the 13mm nut in the boot to bypass the bst box and car cranks fine.Damaged wiring under the car then. A big thanks for the help guys

 

[0l0dom0l0]

Hi thanks for the input, Have just been out and tried what you said with the jump leads and car starts, also tried it from the 13mm nut in the boot to bypass the bst box and car cranks fine.Damaged wiring under the car then. A big thanks for the help guys

Yep exactly as I thought. It's quite a draw on the lead and they're often under rated for the requirements out the factory anyway. So that coupled with damage just simply means it can't handle the current.

 

[Octavius]

Pleased we were able to help.

 

[Octavius]

Hi thanks for the input, Have just been out and tried what you said with the jump leads and car starts, also tried it from the 13mm nut in the boot to bypass the bst box and car cranks fine.Damaged wiring under the car then. A big thanks for the help guys

:headbanger:

 

[gaz123d]

http://s1044.photobucket.com/user/gaz123d/media/IMG_20160123_124834_zpsu8rwgiyw.jpg.html

This is the state of the cables. Shocking

 

[gaz123d]

Just wanted to add the cables running underneath the car thick and thin red hooking up to the boot on closer inspection had been zip tied together and have melted through insulation down to steel wires.
It looks like this cable has been changed before at some point and not been clipped right. Also I have read stuff online about this cable having a recall in canada and usa because of corrosion on end terminals to fuse and battery ?
£160 for new cable then fitting.
Anyway once again thanks to everyone who gave input and helped I hope it helps anyone else with similar issues.
Gaz

 

[Octavius]

Once the terminals are bolted into position I would protect them from corrosion with grease.