Old Dial Honeywell Wall Thermostat Possibly Faulty

[WSB]

My Dad tends to keep his central heating controller set to continuous and just switches the heating on and off when he needs it using the thermostat on the wall.
Possibly a weird way of doing things but that's another story.
Anyway, he was complaining that when he goes to switch the heating on by dialling the wall thermostat to a high temperature, it does not always switch on our tends to be intermittent.
Last time I saw him do this, he dialled the thermostat temperature right up to 30 degrees before the central heating kicked in. The room clearly was nowhere near 30 degrees, so thought then that the wall thermostat was a bit dodgy.
Anyway, now he's complaining that when he tries to put the heating on but turning the dial to 30 degrees, it doesn't always work.
My suspicion is with the wall thermostat and maybe he could of worn it out or damaged it by constantly changing its setting from min to max.

Would you agree with my theory?
Secondly, are these things easy to replace?
It's a non digital honeywell dial type.

Thanks

 

[Wayners]

It's just a switch. Live in and live out.

Swap it

 

[WSB]

It's just a switch. Live in and live out.

Swap it

Do these things tend to wear out if constantly changed?
Are the wires low voltage?

 

[Exedon]

Do these things tend to wear out if constantly changed?
Are the wires low voltage?

Yes they can need changing and normally 240v

 

[gas112]

Have a look at it see if there is a hairline crack in the knob this is quite common and stops them working correctly.

 

[CountryFan]

If it’s only wired as live and switch live could be hysteresis, but if it’s been working fine it’s either on its way out or could be as per @gas112. Yes they are easy enough to change if like for like.