My tub does not want to stay running when i press the button, you have to hold the button down for it to work

Check temperature control relay for early cut out.

If it is a regular gas hot water heater You need to turn the knob on the gas valve to pilot. Depress and hold the knob down. while doing that press the green button on the side of the valve . you may have to repeat that a few times. that button makes a spark to light the pilot. You need to hold the knob down for about a minute more to let the thermocouple heat up and signal the gas valve that it has a flame. release the knob . if the pilot flame stays on ,turn the knob back to the on position. If that does not work repeat if still not working give more info. Make and model of heater

My model is the psp511lca but it may be the same type of reset. I have a dial I turn to the "change filter" option and then press the up and down temperature buttons simultaneously and hold for a few seconds. When you turn the dial back to "run" the change filter light on the display is gone.

F51 error code is a motor rotor position sensor failure or a lower harness problem. You need to check the motor in manual test mode, not automatic test mode. This will check the hall sensors and do a spin test: Be sure the washer is in standby mode (plugged in with all indicators off; or with only the Clothes Clean or Done indicator on). Select any one button (except POWER, START, STOP, and PAUSE/CANCEL) and follow the steps below, using the same button: Press/hold 3 seconds. Release for 3 seconds. Press/hold 3 seconds. Release for 3 seconds. Press/hold 3 seconds.

If this test mode has been entered successfully, all indicators on the console are illuminated for 5 seconds with 88 showing in the Estimated Time Remaining two-digit display. During the 5 second wait time with 88 showing in the display, press the same button once. You should be in manual test mode. If the button is not pressed within 5 seconds, the automatic test mode begins. The Rotor Position Sensor uses Wash, Rinse, and Spin indicators to detect the three hall sensors. Console can have up to two of these indicators on at the same time when the tub is not moving. Open the lid and rotate the basket by hand. The Wash, Rinse, and Spin indicators should toggle on and off according to the direction the tub is being turned.

SPIN TEST: Make sure lid is down. Press and release: 2nd RINSE or EXTRA RINSE. The lid locks and the lid lock indicator turns on. Press and release; SPIN SPEED, WATER LEVEL, or LOAD SIZE. The motor/basket spins at 23 rpm. Press again, motor /basket spins at 530 rpm. Press again, motor/basket spins at 950 rpm. Press again and motor turns off.

From:
http://www.applianceblog.com/mainforums/threads/32879-Whirlpool-Cabrio-UL-F51-Error-Codes

Natural gas or fuel. turn dial to pilot hold down the button. Light with a long grill match or grill lighter. keep holding button until pilot light stays lit when released. now turn the dial to on.

When you light the pilot lite you have to hold the button down until it gets the element hot enough to stay lit. If you hold down the button and lite the pilot and let it go right away it will go out. What to do is hold down the button and lite the pilot and continue to hold the buttn down for about 45 seconds to a minute then let it up very slowly and you will see if it is going to go out by the flame getting smaller as you let up on the button. If it does start to get smaller conitnue to hold it again for a few seconds and repeat the process of letting it up slowly. when the control element gets to the right temperature it will stay lit then turn your valve to "ON" and the fire will start up and continue to heat the water.

A long time ago, in a place far away, I saw an old gas valve, might have been on a water heater, might have been off an A/C unit. I took my 10" adjustable wrench and unscrewed the coil that the thermocouple screws into. Now, when I have the problem that you describe I take the threaded end of the suspected thermocouple and put it into my spare. I light the pilot and hold the button down. Then, after a minute or two, I press the button on my spare, which now has the thermocouple attached. If the spare stays in the "ON" condition, I have just proven my gas valve to have faulted.

I suspect you main gas valve has failed, if you can find another valve, you can test as above, before buying a replacement valve.

Are you holding the button down for a minute or so after you light the pilot before releasing the button?

If so, almost certainly, your thermocouple is bad. This is the long tube which runs from the control box to the pilot flame. Remove this tube, take it to the hardware store and get an exact replacement.

Once the thermocouple is replaced, your pilot light should stay on.

turn the gas valve button to piliot position, push it down and hold it, click the ignitor to light it... look thru the site glass to see the spark all at the same time, if it lights hold the button on the gas valve down for 30 seconds, let it up if it doesn't stay lit you need either a thermo coupling or a gas valve thermo coupling would be the first choice, the is also a filter around the bottom of th tank near the floor it needs to be clean that is the only soirce of air to run the heater