I HAVE A AMANA PTH153B50AE PTACT UNIT. ANOTHER

Question edited for a lot more clarity.

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Probably this one. Talk to your installer.

https://www.amana-ptac.com/products/ptac/hec154j

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http://www.h-mac.com/product-catalogs/amana/Amana-RSKP0009-Installers-Guide.pdf

probably low on freon

I don't see this error code in the manual. I do see nP as an error code for Window Switch lockout. I just had this happen to me and they had me reset the control board.

Remove case, flick master switch to OFF for 10 seconds. Press Heat/Cool same time turn switch back on HOLD until off light comes on.

You should be fixed. Just had to do this for my unit. I was playing around with the settings and turned on the window switch option by accident.

I have the same problem, and I found the manual reset inside the unit. Turn the power off, and unplug the unit. Remove the outer cover of the unit ( inside cover ) , and remove the 2 screws holding the " wire mesh " in the front of the cover. Pull the wire mesh up and out of the way, then carefully pull out the heating element.
On the heating element, where the wires are connected, there is a manual reset button... Push the button in, till it resets...

My reset was on the upper left connection of the wires... just looks like a small push button, but the reset is recessed a bit.
Replace all covers and plug back in.. working fine..

sound like a thermister problem, however this may also be a circuit board problem, the system is controled by the outdoor board, check to see if you have a blown inline fuse in the outdoor unit, it will be under a red case in one of the wires.

check to see if unit has a contactor,they arc and weld together,keeping your unit on

most boards have a small 3 or 5 amp fuse on the board it looks just like a car fuse. do not put in wrong size fuse it can allow damage to the board.

Onl full service comes to mind.

u must check if the unit outside is working when u turn on your air conditioner.