Battery connected up wrong way round!

The alternator is probably not going to be very well, other electronics too. All you can do is reconnect watching for any massive sparks as you stick the second lead on. I would be amazed if everything is OK

Older diesel, or an extremely old petrol car if it ran with the battery connections reversed. One with no electronics for the engine whatsoever.

Well depends on the amount of electronics in the car it might -just- have survived serious damage. Where did the smoke come from?..

You could try re connecting I with a low ish value fuse in line like say

Still how did it start and run?

DC starter motor will go backwards if the wrong polarity voltage is applied (which is how model trains go backwards). I don't think an injection pump works backwards. But that would only be if you had stuck a jump lead directly on the main terminal of a pre-engaged starter as solenoid is directional too so wouldn't engage the starter or make the main circuit (which is how the point motors work).

I suspect starter motor. So knackered by years of excessive cranking that once it got a fully juiced new battery the current has just burnt it or the solenoid out. Or maybe solenoid has been slammed so much harder "on" than it's been used to it's wedged on muck and stuck on.

With everything off put a smallish (21w indicator) bulb between the battery +ve and +ve terminal. If it lights then something is pulling current (alarm?). Put bigger bulb in circuit - 60W headlamp. If that lights brightly then something is pulling a lot of current - alternator diodes blown? Unplug / disconnect things like alt and starter until you find what is pulling the current.

Some do, some don't, Older JCBs used to be quite good at running backwards, you'd kick it over, the back pressure in the hydraulics would bounce it backwards & then everything would behave very oddly

Yep. 1996 mini.

Not sure but I think alternator. That seems to smell a little now. Hosed?

A permanent magnet motor will go backwards, but reversing the supply to a non-permanent magnet motor will reverse both the rotor and stator fields, so it will still run the same way won't it?

SteveW

yes, absolutely and proved.

Only if a permanent magnet type. Series wound ones ain't polarity sensitive.

Right - and they still used points ignition then?

With a bit of luck, only the alternator has suffered.

Yes. Realised this about 1 min after posting. Some Fords (Mustang) have perm magnet starters, I don't think a Mini ever did.

Solenoids with soft iron plungers magnetise the soft iron in the required N-S orientation to the coil to work with either polarity. Otherwise all relays would be marked with +ve and -ve coil terminals.

So it could crank and would crank the right way.

Scratch this one.

In article , Dave Plowman (News) scribeth thus

Interesting that. Suppose it does depend on the way the output is presented to the outside world especially the control side, the actual power generation side will have rectifier diodes that will prevent the reverse current flow..

We used to convert Mini's to Negative earth many years ago. Reverse the battery and "flash" the dynamo coils and IIRC that was about it..

Worked every time...

If the battery's connected the right way round, if it's connected the wrong way round then they'll conduct.

plus reverse the coil connections or you get a weaker than normal spark

They prevent reverse current flow from the battery into the alternator when correctly connected. Do quite the reverse when reversed. ;-)

And swap the coil connections. In theory, at least. And hope it didn't have a radio. Unless valve.

that is odd cos metros had electronic ign. from the mid 80s. and after '92 everything went injection and electronic ignition, shirley?

Utterly amazing. Most BL products had electronic ignition a decade or more earlier - to allow longer service intervals.