Replacing Shower Switch

I am trying to replace my shower switch which recently broke.

I have purchased a new 45 amp switch which is ready to go.

I have isolated the shower power using the fuse box downstairs.

Before starting to remove the cables from the old switch, I used a multimeter to check the voltage, I am getting a solid reading of 7v from the live.

Is this normal? Why is this?

It might be picking up some  induced voltage from other cables  on the way ...strange things happen .     Try killing all the circuits . 

Have you removed a fuse or switched a circuit breaker off ?

Some cheap multi meters can't be trusted to be honest , so it could be nothing .    Is it digital ?      Usually a stray induced  won't power a light bulb  ( old fashioned type)   6v  - 12V    it just goes away . 

Is the voltage on the earth wire? 

Is there an RCD in the circuit ?  

Its concerning  though , if you isolate you expect it to be dead .  

I don't know how skilled you are  working with electrics ...if I were there  I'd try disconnecting  the L & N  in the board  to see what happens ,   MCB could be leaking current across  or an old fuseway with the fire retarding pad showing signs of tracking from too many blown fuses  ...can also leak some voltage . 

I think we'd all agree to running tests on the circuit . 

As what Evans said above, almost certainly an induced voltage, knock off whole board if you are worried. 

Is your shower circuit isolation double pole, (I.E. breaking both live and neutral), or just breaking the live side? 

What points are you measuring between? 

There is often a small voltage between earth and neutral which is harmless.

A statement of 'solid reading of 7v' on the live needs clarifying where the other meter probe is and is this an AC or DC voltage your meter is showing? If this is an actual voltage it could be that the "live" is at zero and your other reference point is where the "7" volts is. However a multi-meter is not an approved device for checking safe mains isolation, so your "readings" actually prove very little and I am not convinced you actually have any voltage at all?

I am also concerned that if this is a cord-pull shower switch, and it is square shaped, it can end up been at best unreliable and at worst dangerous if replaced by a DIY'er, as it is almost impossible to ensure you get a sound mechanical connection on the cable joints, which are then a potential fire risk.

Doc H.