I have plenty of piping hot water in the bathroom sink. But, lukewarm water in the tab next to it.

It is a simple 4-way valve behind the wall for the tub. 2 Inlets, one for hot water and the other for cold water. 2 outlets, one for the tub and the other for the shower.

The cold water knob is always turned off. But, I still get only lukewarm water in the tub. It is even if I try to use the shower.

Any suggestions/solutions for the problem is welcome.

This is an old house. There is no mixing valve to mix hot and cold water.

Thank you very much

Can you give us a brand name for the valve? Is this a two or three handled valve? Let me know, tom