Battery isolator stops van starting

[mjsroofing]

I remember when I had my mk6 transit, if the battery went under a certain voltage it wouldn't even try to start, slight touch of a jump lead and she'd fire up.

It was as though it had a cut off switch, under certain fraction of a volt and the ecu don't activate the starter or something.

If this is the case maybe the isolater is drawing the voltage down a little bit.

[Bewick]

So, replaced the isolator switch with thishttps://rover.ebay.com/rover/0/0/0?mpre ... 1977293253

Same problem. With the switch in place (in the negative) and it deisolated there's current to operate the radio etc. When I turn the key all the usual lights come on but it won't start, same sounds as when the battery's flat

BUT

When I connect the negative straight to the battery without the switch in place she starts fine. Why does having the switch stop the van starting?

I'm struggling with this one now.

[the dutch guy]

Please draw the schematic how it is connected now

[Bewick]

I can't draw it I'm afraid but I can try to describe.

I took the negative cable off the battery and put it on one pole of the switch. I then ran a fresh cable from the switch to the negative battery terminal. It works to disconnect. It works to reconnect and run the central locking and everything, just not to start the engine.

I hope that's clear. It's very simple wiring so I hope I've done something obvious wrong rather than needing to buy yet another switch.

[knobby1]

I can't draw it I'm afraid but I can try to describe.

I took the negative cable off the battery and put it on one pole of the switch. I then ran a fresh cable from the switch to the negative battery terminal. It works to disconnect. It works to reconnect and run the central locking and everything, just not to start the engine.

I hope that's clear. It's very simple wiring so I hope I've done something obvious wrong rather than needing to buy yet another switch.

I wonder if the switch can "actually" handle the quick high current hit when the starter is first activated..?? Some cheap ones say they can but throw in the towel when it comes to delivering the current.

Lord Knobrot

[dumper]

When I fitted a master switch to my mk6 instead of using cable from battery to master switch I used a flat pice of bar drilled a hole in each end and bolted master on one end and battery on the outher end but I had the room to do so as it only had one battery the switch I used was a heller heavy duty one that we used on Crains and diggers at work