Weird A/C problem

We have a small (about 6000 btu) A/C mounted in the wall of my bedroom.
I like it a little cooler while sleeping and with the kids gone it allows us to turn the central unit almost off at night.
It has electronic controls with a remote and a LED temperature display.
When you set it on the economy setting the fan goes off when the compressor goes off.

Problem is if you set it on 68.
It will come on and cool the room to 68 and then shut off.
But the temperature display and I assume the thermostat will continue to fall.
I have seen the temperature display in the high 30's or low 40's when the room is at 70 and it is above 70 outside.
This causes the unit not to come back on when the room warms up.

Now here is the weird part.
If you manually turn it on or set it on cool where the fan runs all the time and just the compressor shuts off the temperature display and thermostat work perfectly.
It has me stumped.

In short if the fan is on and drawing air threw the unit the thermostat and display work but if you shut the fan off and the unit is just sitting there it reads really cold unreasonable temperatures.
 
sounds like , with the fan off, the temp probe is reading coil temp. due to the sensor laying against the coil, locate the probe (sensor) and move it away from coil, sensor is usually on the discharge air side (room) of inside coil
 
Try moving the temp sensor away from the inside coil. (Evaporator) behind the filter. The senson to close. When the unit equalize will make the coil colder. Thats what its seeing.
 
The thermistor sits really close to the cooling coil. When air isn't flowing, then the thermistor reads just the temp coming from the coil, which is much colder than room temp.

You can get an aftermarket thermistor that is longer than OEM and then route the new probe so that it sits outside the A/C, or at least far enough away that it doesn't pick up the cold of the coil.

You can find replacement probes on Amazon, but there's also likely an appliance place near you that could order the correct probe....for a slight mark-up, you know. :wink:

https://www.amazon.com/s?k=air+conditioner+thermistor&ref=nb_sb_noss_1

You might also be able to simply move the existing probe farther out from the coil so that it's not picking up the coil temp when no airflow is present.
 
OK I took the filter off and the temperature probe is in plastic piece that sticks into the fins.
It was not touching the fins. Was about 1/2 inch from fins.
I moved it out a little more to see if that will help.
The tube coming from the probe may have been touching in spots so I tried pulling it away also.
If this does not work I will try to route it to the dirty side of the filter and see if that helps.
 
Don't hold me to this, but I don't [i:3a691dd3d3]think [/i:3a691dd3d3]the 'tube' matters if it touches. I believe the only part that matters is the tip, where the actual probe is.
 
If that filter is really dirty, it could be icing up around the probe, and with the fan on all the time, it would melt it off when compressor shuts down, clean that filter! :lol:
 
The unit has a warning light that comes on to tell you to clean filter.
It must be based on run hours because the filter is barely dirty when it comes on.
I have never seen any icing of the coil.
If it makes a differance I did not notice this problem last summer.
It just started this summer.
The unit will not be 2 years old till next spring.
 
I have four window units from 20,000 BTU to 8000 BTU
and I never run them on auto because the temperature
rises too much before they cycle back on. It also seems
like they get more mold in them when they are in the
auto mode.
 
That economy setting is misleading. Every time the unit reach's set point and go's off there are still btus available "IF" fan continued to flow air across coil while refrigerant continue's vaporizing in coil. Instead,most of the cold vapor go's outside to compressor and condenser to be lost. The difference in cost to run fan continuous is pennys a day. The bonus cool air more than offset's cost to run fan. Moving sensor away from coil might change displayed readings but the effects remain exactly as before. Turn the sucka on and let it do it's job.
 
If the temperature bulb works fine on one setting and not on another it isn't the bulb. Most likely an issue with the control. You might try unplugging and resetting it.
 

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