Happy you got it sorted in the end Woodpole man .
I see this kind of trouble every week ....multiple visits to garages , auto electricians, and vists to the dealerships , scans sent to Germany and so on ...
If the scan does not show it , if the ODIS /VAS test plan does not help load up the parts cannon and fire various items at it in a vague hope you may stumble on the problem , all at owner / customers expense of course .....dealerships are the worse in my experience
The scan will not show anything as the starter in itself is not under diagnostic scrutiny......yes it has battery monitoring module but at cranking amps levels it’s of no use , could the battery monitoring module see a bad earth pathway , could it see a burned terminal , high resistance or frayed heavy cables a bad armature on a starter motor ....... not a chance .
If you have either a starter that does not crank over or cranks slowly or cranks slowly with no start or intermittent start , or delay before cranking what i would do is rig up a halogen bulb onto the starter solenoid terminal ...using a halogen bulb you can determine that the supply has some grunt behind it ,the bulb will pull out around 4 /5 Amps , next .....one channel of scope onto battery , second channel use a 1000 amp range inductive amps clamp around starter heavy cable
All sounds easy doesn’t it ......but accessing a starter on newer cars can be a job in itself .... but to carry out the nessasary diagnostic pathway tests it’s where you need to go ‘ most folk will bail out at this point because well .... it just to arkward to get at and then revert to ‘ guess a part ‘ method .
So watching amps clamp and battery on scope channels ,and your halogen bulb .....crank it over ...... does bulb light ...if yes now watch scope channels ....if no wiring checks back to crank relay or module authorisation and so on .
So it’s cranking over ......does scope show mega high amps starting peak and continues throughout extended cranking ....does battery volts stay around 10.5 volts under cranking ......this shows battery has got grunt behind it to keep pushing the high amps and holding the volts .....this shows battery is good , battery volts can drop a little more than the happy level though
Does battery volts drop considerably and amps drop away .....battery duff
Next volt drop testing on heavy cables or substitute heavy cables , is earth pathway good from starter to block or gearbox .... volt drop tests or substitute heavy leads with jump leads .
So all these tests carried out and starter is taking massive current to get it going and keep it going and battery volts a little low suspect starter motor ....or some kind of mechcanical resistance ....if vehicle runs well with no other symptoms ...loss of water etc. we can rule out other issues for mechcanical resistance .
Have this mantra ...... test not guess ..... if I fit part X or Y and it does not fix it then what ?? Rule out all other possibilities first and not after you have fitted part X or Y
Again happy you got to the bottom of it in the end 👍👍
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