You need to check your hot/cold handles or the shower spicket. Not sure what type you have, but they come off. More than likely you need to just replace a gasket..
The difference between a shower and a tub is the shower tends to enclosed with water that comes out of a shower head above while a tub has a faucet that pours into a large basin.
I just brought a Glacier Bay pull down ceramic kitchen faucet Model 896408. After installing it, the cold water wasn't coming out of the faucet. It turned out the problem was the coldwater supply line inside the faucet was bent & twisted. As a result, when the body of the faucet was attached, it had to be turned just a little to position it correctly, this tighted and choked the water supply line even more- which meant "no cold water." Waiting on replacement line from Glacier Bay, which, I am certain, will correct the problem.
Employ a plumber.
First make sure that the hot and cold supply lines (the plumbing) aren't backwards (hot should be on the left as you are facing the faucet) or that someone accidentally ran two hot lines. For the problem to be in the faucet itself you would have to have a single handle faucet. If this is the case the control valve is broken and should be replaced. Three handle Left= Hot Water Flow. Right= Cold Water Flow Center= Controls whether the water comes out the shower head or tub faucet. Two handle Left= Hot Water Flow Right= Cold Water Flow (Diverter Valve is elsewhere if it's a tub/shower) Single handle One handle controls both water pressure and temperature
If the tub has a shower as well, the pipe from the faucet to the shower head could be leaking. You might also check the tube that comes OUT and fills the tub. It could be leaking back at the valve when you turn on the water.
You don't say whether you are referring to a single handed mixer or an individual faucet. If a mixer then the o rings inside have probably worn away and need to be replaced. If a single faucet then either the washer needs replacing inside the tap or the gland nut (if have one) needs to be serviced. Dont forget that in a single knob faucet, there is also an adjustment to be made for the hot water temp. that comes from the shower when turned to hot....it is a sort of dial in system remove the knob handle with a Philips screw driver and see where the settings are if too high adjust down a few clicks(notches).
Remove the handle, turn off the water with a wrench and reatache the handle in the correct position. Good Luck
It is not supposed to be on when engine is running unless there is a problem.
Supply line clogged. The end of the stem where the washer is may have broken off so that the faucet isn't really opening. Shut the water off and take the stem out of the faucet and see what it looks like.
There are many faucets that do this. There is water between the end of the faucet and the valve. You turn it off, and the water comes out of that area. Unfortunately, there's not much you can do about it.
Check the supply valves. Chances are the hot water supply valve is not fully opened.
Narrows.