Replace Stairlift Charging Plug

My 90-year old mother had a stairlift fitted 10 years ago. The unit charges via a thin two-wire cable and integral 3-pin plug. For some time now it has been clear that the connection in the back of the integral plug was breaking up because the stairlift unit beeps when it is not being charged and she has to wiggle the wire at the back of the integral plug to stop it beeping (i.e. to remake the connection and get it charging again). We should really have attended to this but she has been very ill recently and we have had other priorities. The connection now seems to have broken completely as the unit beeps all the time and wiggling the wire no longer fixes the problem. The stairlift company cannot attend until Monday and have a £60 call out charge. I am assuming that I could cut the cable at the back of the plug, separate the two thin wires and reconnect it via a standard household 3-pin plug to get it charging again. But which of the two thin wires is the live wire? One is black and the other is black and light grey.

I have a photo but have not been successful in attaching it as the Forum Post page is telling me 'You do not have any existing attachments'

Hopefully an Admin  will  enable you to post a photo .

Meanwhile   I'm guessing the flex is mains voltage   (240V )       Has the cable  been flexing  and finally worn out ?              Is the 3 pin plug  like the ones you see in the back of a kettle  ?   

Understandably you need it sorting  as quick as possible .     We need a photo .! 

Are there any markings indicating voltage or mA or A? 

Most stairlifts are battery powered so what you are talking about is the charger or the mains lead for it. Here are some examples https://www.ebay.co.uk/sch/i.html?_odkw=stairlift+power+lead&_osacat=0&_from=R40&_trksid=p2045573.m570.l1313.TR1.TRC0.A0.H0.Xstairlift+chaeger.TRS0&_nkw=stairlift+chaeger&_sacat=0

Until you can post a picture give more details.

Is is a standard moulded plug with a flex and a connector of some sort or is it a "wall wart" type power supply wit a dc output.  Make and model of stair lift would help.

if you have 2 thin wires black and light gray that suggests a ELV supply from the output of a plug in transformer. if so, connect them to a normal plug and expect some smoke to escape. and itll cost more than the £60 callout

Thanks all for these prompt and helpful replies. It has been pointed out to me here that the 3-pin is not just a plug, it is indeed a transformer, so Dave and Andy are correct. That being the case, we will have to wait till Monday for the engineer..........

Thanks all for you help!

Reality the transformer could possibly be replaced with a similar equivalent from somewhere like maplins??( are they still trading)