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Dead Short
https://www.ausmini.com/forums/viewtopic.php?f=2&t=71902		 Page 1 of 2
Author:  brett [ Sun Jul 17, 2011 7:41 pm ]
Post subject:  Dead Short
Hi guys, any ideas, trying to get the Cooper S restarted, and after a bit of cranking the battery cables can get very hot. Any ideas?

Can't see any regular wires getting burnt. so it has to be soliniod or the starter. neither items get hot
Cheers
Author:  simon k [ Sun Jul 17, 2011 8:08 pm ]
Post subject: 
was wondering that in regards to your little fire...

starter motor drawing too much current = try another one
Author:  brett [ Sun Jul 17, 2011 8:18 pm ]
Post subject: 
Thinking that! Its a new Solinoide It was Working fine, before I had the engine soda blasted, and havent been used in 7 months, so I wonder what could have happened??
Author:  kiwiinwgtn [ Sun Jul 17, 2011 8:30 pm ]
Post subject: 
Check your earth connections, especially the one to the body in the engine bay

Paint is not a good conductor

Also the solinode plate is an earth and needs to be clean

Kiwiinwgtn
Author:  simon k [ Sun Jul 17, 2011 8:30 pm ]
Post subject: 
brett wrote:
I had the engine soda blasted


what state was the engine in when you had it soda blasted? was it assembled - IE with the starter motor on it?

they're not especially well sealed...
Author:  brett [ Sun Jul 17, 2011 8:48 pm ]
Post subject: 
The engine was assembled. and I haven't removed the starter motor yet. It was all sealed up at the back so none could get into it. But maybe some got into the starter motor!
Author:  simon k [ Sun Jul 17, 2011 9:00 pm ]
Post subject: 
brett wrote:
But maybe some got into the starter motor!


that's what I meant.... but dunno
Author:  brett [ Sun Jul 17, 2011 9:10 pm ]
Post subject: 
its more the leads getting hot now, when the engine if being cranked.
We have used new cables, and they are fine when we are not cranking, its just when we crank it to try and start it they get hot!
Author:  Morris 1100 [ Sun Jul 17, 2011 9:14 pm ]
Post subject: 
Are the leads too thin?
Author:  drmini in aust [ Sun Jul 17, 2011 9:17 pm ]
Post subject: 
Morris 1100 wrote:
Are the leads too thin?

Starters pull 200A or so when cranking, the original battery cable is THICK for this reason. :wink:
It minimizes voltage drop to the starter.
Author:  Lockie91 [ Sun Jul 17, 2011 9:21 pm ]
Post subject: 
kiwiinwgtn wrote:
Check your earth connections, especially the one to the body in the engine bay

Paint is not a good conductor

Also the solinode plate is an earth and needs to be clean

Kiwiinwgtn


I second this.. all that paint in your boot and surrounds I saw, won't help this.. scratch some back at the point where all earth connections are in the line, and then try again.
Author:  kiwiinwgtn [ Sun Jul 17, 2011 9:24 pm ]
Post subject: 
heat is converetd energy, if the current is slowed down getting to the starter motor it has be be used some where, heat is usually the outcome

Sounds like a bad connection or earth or buggerd starter motor

How long does it take the leads to get hot, most leads get hot after less than a minute as there is a heck of a lot of current passing thru the leads.

Also how hot, to hot to touch or smoking hot..
Author:  simon k [ Sun Jul 17, 2011 9:45 pm ]
Post subject: 
Lockie91 wrote:
kiwiinwgtn wrote:
Check your earth connections, especially the one to the body in the engine bay

Paint is not a good conductor

Also the solinode plate is an earth and needs to be clean

Kiwiinwgtn


I second this.. all that paint in your boot and surrounds I saw, won't help this.. scratch some back at the point where all earth connections are in the line, and then try again.


if there is a dodgy connection somewhere, less current can get through, not more - if the cables are getting hot, then too much current is being drawn...

so if there are bad connections, the starter will turn slowly or not at all

if it was the same cable as before the car was taken apart, then the only thing changed is the starter motor - two bolts and it's out and another one is in and you know what to do next
Author:  mini_mad_matt [ Sun Jul 17, 2011 10:12 pm ]
Post subject: 
As kiwiingtn mentioned, how long were you cranking it for? The starter system isn't designed for continuous use. It all gets very hot the more you use it.
Author:  Mick [ Sun Jul 17, 2011 10:34 pm ]
Post subject: 
There's some mixed messages here.

Heat can be caused by two things, both related to Ohms law: Heat = I^2xR

So you only get heat if there is current or a resistance.

If the heat is localised, then it may be a bad electrical joint (at the point you find the heat only, no where else) caused by cracked or damaged cable core conductors, or a poor contact in the solenoid. Check the voltage drop across the solenoid (put your multimeter from input to output studs on the solenoid while cranking the engine) to see if there is a voltage drop here. There should be next to no volts measured here to indicate a good solenoid.

If the heat is more generally anywhere along the cable, then it can be just a case of the engine being turning over for a long period. The battery cables are a balance between economy, and capability. They are really only designed to be used in short bursts.
But if the battery voltage is good, and the solenoid is good, and the engine turn over is weak, then the starter motor will have a few shorted turns within, and require a rebuild.
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