Car electrics problem

Swimbo says she had unlocked car with fob (Old shogun diesel with a GT alarm and immobiliser) Got in and tried to start engine all panel lights etc came on engaged starter and heard I think the solenoid click, panel lights went out and no electric power it also locked the 2 front doors so she could not get out.

Tony

Sounds like an earth problem. Chances are there are two (or more) earth routes but the main one (the strap) is needed to start the car. The others will have too high a resistance to carry the cranking current without too much of a loss of voltage. They will, however, pass the smaller currents you referred to in your other post without a real problem.

A dirty battery (or high current solenoid) connection can cause the same problem.

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Just a thought, but if the main earth strap was broken, then maybe the starter motor current has done something nasty thing to whatever conductor tried to pass that large current! Yes, well worth checking all the earth connections you can find.

When the earth strap on my SD1 broke, the throttle cable became the main earth path and melted the inner plastic lining effectively welding it solid. On some cars the path may be through other parts of the wiring and cause serious damage to it - even a fire.

Replaced earth strap

Hoping all is well everything appears to work

There was still a strap between the battery and car body and from there another strap to the chassis

Not sure yet how the circuit would make to the engine.

Tony

That's the problem. Could be many things - gearchange, accelerator linkage, clutch linkage etc etc. Non of which designed to handle several hundred amps. The real problem is where there is another electrical earth designed for a low impedance connection to the fuel injection etc - for perhaps interference suppression. If that gets the full current of the starter motor it can burn out.