Rheem Rakb-018jaz outside ac unit fan wont turn off. Thermostat is not turned on. Worked fine yesterday.Live in Nebraska

Question edited for a lot more clarity.

First try disconnecting from mains power for two hours, or even better overnight. This resets the control board and when you switch back on it will go through a self test procedure.

https://www.google.com/search?q=rheem+rakb-018jaz+reset+button

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The bearings are bad in the motor and after the fan runs enough it eventually gets hot, making the bearing screech and the fan locks up. Need to replace motor again. See if it has a warranty. The reason it gets hot is because the fan is what removes the heat from the coil and if the fan isn't running there is nothing to cool it off so to speak.

Unless you just installed or had the thermostat installed recently, I would not point at the thermostat as the problem. With what you have described I would suggest have your units serviced as it sounds like a loss of charge, or failed defrost control board. The "Aux" comes on when the unit is using secondary heating (electric heat strips). That occurs when the demand temperature (what you set it to) in Heat mode is more than the current room temperature, usually ~2-4 degrees higher. Also happens in defrost mode. Defrost is a heat pump cycle that melts any build up of ice on the condenser unit (outside unit). That process is simply the unit running in cool mode which will heat up the outside unit to melt any ice. Defrost cycles vary with manufacture but usually you can tell if is in defrost by looking at the outside unit, during defrost the unit will be warm or hot sometimes there is steam and the compressor will be running but not the fan. Defrost only happens on heat pumps in "Heat" mode. Rheem has a 10 yr compressor and parts warranty, so call the installer or Rheem authorized service company.

You need a "Y" terminal. "Y" is pretty standard on every heat pump. It is the wire that will energize the compressor contactor at the outdoor unit, allowing the compressor and condensor fan to run.

no this is not normal. the fan should stop running when the thermostat is satisfied or when the heat pump goes into defrost mode. if it is running nonstop, there is a contactor that operates the fan and compressor that if it sticks will get line voltage to it. you would have to take the cover off of the outside unit and turn the thermostat to off. If the fan continues to run, you need a new contactor.

Let's start out by your statement that the fan would not run, then you changed the contactor, not it won't stop running.
I believe, based on your info, here's what you need to do. Kill power to the unit. The 2 wires bringing power to the outdoor unit should be on the top 2 terminals. The 2 fan wires should be on the bottom 2 terminals. This is providing that the contactor is mounted Vertical. The could be an outside chance that the unit has a short in it and you are getting voltage feedback somewhere.
Take another look.

I would probably start at the thermostat and see if 24 volts is continued to be applied to the yellow wire which calls for unit activity even though you have called this off. Shorting the cool (yellow) wire to the return (red) wire will cause the HVAC system to begin cooling and the fan will be turned on automatically.

Trace the wires (small cable) going to the out door unit. This is your 24v control circuit. when it enters the outdoor unit it ties to wires routing through the inside of the unit trace these down. For AC units 1 usually goes directly to the "contactor" (the item you push in and the unit runs?) the other wire can also go to the other side of this same item. But I suspect it goes through other tings before it finally gets there.
Some items are the high and low pressure switches and a delay timer.
A red button sticking out where you can reset it is the high pressure switch and if it clicks and lets it come on you may have a dirty outdoor coil or a fan motor outdoor that is not operating all time.
A low pressure switch has no reset normally on AC or HP.
A delay timer will have 2 3 or 4 wires depending on the type of timer. 1 of these wires goes to the contactor (usually) and one of them feed this wire. remove the wire going to the contactor. now 1 at a time take the other timer wires and touch them to the wire just removed. if the times is bad the contactor will click when you touch one of them with the removed wire.

If its a heat pump you will have to make the contactor try to come on around the board. and this you will need some knowledge on which and what feeds your contactor. Here Id suggest a technician. If I had a way to see your setup and wiring I could talk you through this but its too hard to type and would take way too long.

hi! there,
well we have to do something about that,if you mention of fan spin and it pushes air but no cold enough on it,this refer to blower on compressor, there is fan on outside the condenser,so we are on blower w/c does not blow enough cold air,there are factors we can check,first thermostat try to adjust thermostat to the coldest point,
observed if cold was increasing if not, 2nd have clean the filter from evaporator it may have a clogged, check evaporator if there freezing ice on bottom portion of evaporator w/c cold was coming out,have it clean,cleaning this is done by certified a/c technician,there is problem if have an insufficient cold,this is the symptom of your system was under charge lack of freon,this can check by technician w/ clamp ammeter device.the operating current should be equal to rated current on manual,inform service center about this,have a nice day don't forget to rate me.thanks's

Hi Phillip,

Check your thermostat wires to see if you have any of them which are bare and touching. If any are touching separate them and tape em up and try unit again. You have a direst short in your cooling portion of the unit.