Hi my alternator is getting very hot without the ignition on and the car has not been running. any idea please 

15 minutes ago, Peter3015 said:

Hi my alternator is getting very hot without the ignition on and the car has not been running. any idea please 

I'm just curious (someone clever will be along shortly to give you a proper answer). But, how did you discover that your alternator gets hot? Most of us wouldn't be opening the bonnet to check such things...

I got the car the other day and the guy said it needed a new alternator and the main lead that bolts on to it was disconnected so I got an alternator and swooped it and when I connected the battery the alternator got very hot without even turning the ignition on 

Sounds like the replacement also has a fault, possibly one or more failed rectifier diodes. If it's drawing enough current to get noticeably hot it will very quickly flatten the battery.

Yes that is what is happening. I got the car home as I took a fully charged battery when I picked the car up about 50 miles and just got home the steering got very heavy just a few corners from home 

The alternator gets that hot you can not keep your hand on it and like I say this is with no ignition on or engine running at all

4 minutes ago, Peter3015 said:

The alternator gets that hot you can not keep your hand on it and like I say this is with no ignition on or engine running at all

That sounds like a potentially hazardous fault if it gets that hot, a definite fire risk. I'd disconnect it and get a further diagnosis done ASAP.

Yes I disconnected the battery straight away 

2 minutes ago, Peter3015 said:

Yes I disconnected the battery straight away 

Just another thought, I'd be very suspicious that it was sold to you 'needing' a new alternator. If I was a cynic, I would think the seller knew there was alternator issues, and passed the car on to someone else to sort. Unlikely to have 2 x alternators faulty (though not impossible), but I would suspect a wiring fault along the line...

Ok so what would be my best option ? If I disconnect the lead from the alternator the car will start and run fine but obviously will flatten the battery.

1 minute ago, Peter3015 said:

Ok so what would be my best option ?...

If it were me, I'd get the car to a local autospark to have a proper look/diagnosis before you car disappears in a puff of smoke.

Sounds like a plan ok thanks for your advice. 👍

I've been racking my brains to think what possible wiring fault could produce what appears to be an internal failure on the alternator (and which could have been the same with the original). As far as I can see there is just a substantial cable going direct from the alternator to the battery via a fuse in the engine bay fusebox. There is only one thing that comes to mind : cars of this age are fitted with the 'smart charge' system whereby the alternator is externally controlled by the engine management control unit. This control is via a separate connector on the alternator. I think I remember reading on here that if this connector is unplugged the alternator will revert to a standard system.

I'm just wondering if it's possible that a short or incorrect signal on this control wire could be the guilty party. It might be worth disconnecting it to see if that makes any difference, if you haven't already.

Edit: On further consideration I don't think there's any way the smart charge circuit could cause the alternator to draw current from the battery. It's far more likely you've just been very unlucky and have picked up another faulty alternator.

If you find the cause please come back and let us know.