Hot water downstairs but not hot water coming from bath tap?

[J7223j]

Have a mixer tap on bath and a boiler with a tank in the loft. Have hot water downstairs but not on the bath any ideas what would cause this?

Thanks

Am suggesting you ask @pigletjohn for advice.

He is always fabulous with plumbing issues like this.

Is there a switch in the airing cupboard that has sink on one side and bath on the other? Might be worth a try

hot water in sink upstairs?

Do you have hot water elsewhere upstairs? If it's only the bath, is it a thermostatic tap?

If not, if you turn the tap all the way to the hot position, does any water come out?

Do you mean cold water comes out when you turn on the hot? Or no water?

Does the basin tap work?

Post a pic of your bath tap and basin tap please.

When was the bathroom fitted?

When did the bathtap last work?

Have you got a hot water cylinder? What colour?

Sorry I meant water is Luke warm coming out of tap. Not tap as such it’s a mixer dial on the bath that the water comes out of. It’s a round dial with a spout at the bottom. A hot water cylinder in loft usually the water is pretty hot.

Picture of bath filler

How's the basin?

Show me the mixers

When was the bathroom fitted?

Does the spouty thing move like a joystick? Left, right, forward, back?

I think it's the tap. Probably a ceramic one with gearing. Either that has failed, or, if it is a thermostatic tap, its thermostat.

If your bathroom is quite new, there may be a temperature limiting valve on the supply pipes, which adds cold to the hot to prevent scalding. Very common in hospitals and care homes, not so common in houses.

None of those is a DIY fix, especially as you have a weird unusual tap.

It would be useful to know about the basin tap.