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My central ac system occasionally runs too long and the temperature gets way too cold. The digital thermostat reads that the temperature is too high so the ac still runs. This doesn't happen all the time but last night we had the thermostat set on 74 and when my wife got up during the night it was 67 degrees in the house (another thermometer read 67, the thermostat read 78)

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  • Anonymous Mar 25, 2014

    Have a Liebert unit for a data center that is tripping on high head. Suction and Liquid readings are good, and it will run until we hit cold weather (Logs show it usually happens on a cold night) ... Tested electrical and everything is good there as well. Thinking it may be a problem masking an even bigger problem...


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I have seen this is many digital thermostats. The worst problems usually come from the touchscreen thermostats. I would suggest installing a new thermostat. Make sure that you read the instructions before you even remove the old one.

Posted on Jul 03, 2008

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Posted on Jan 02, 2017

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If my freezon would be low then why is it very cold air when I'm going on the road

because the temp difference between the hi and low side will be greater faster than a normally charged system the reason it cycles off is the keep the evap. from freezing up, but running to low on Freon can cause poor lubrication in the compressor causing damage to the compressor, yes it will blow very cold for a short period of time with a low charge

Oct 14, 2015 | 2004 Dodge Neon

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I changed my thermostat and temperature sensor with AC the temperature gauge max out, it takes 45 minutes to max out, now the same issue still exist. Thank you and God bless.

no engine size stated, so there will be no Exact answers ever...
for that one fact..... (most posters fail here)
ok engine temp gauge, so....
ambient temperature is what,
are you at high altitude, ? or cold outside? just a clue here...
it's 100F here, so...
where the parts Jeep parts or aftermarket, ?
the thermostat, is it 180F, or higher, its stamped on this part.
wed need to know that, for sure.

ok, you got the wrong parts.
the dash guages is only a toy , we use a real pyro gun to read temps. at the STAT housing !!!
is the fan for RAD kicking.
not using real tools and real temp guages, means you are just guessing...
consider this.
old stat was bad, (most old ones are, they are short lived)
say it reads too low all the time, so you learn and expect its bad habits,
then put in the correct stat, (not stated what)
and now it works correctly
you had the 180F stat then put in the 200f and it runs hotter.
did you know the stat temp is regulated by the EPA here
are you here, ?USA? or not.
they make this car in Europe too, so..... (laws there are diffr)

Stat put in upside down.
or not with bleed hole (jigglepin) not up hill.
or have air on top of loop, causing the stat to go nuts and the ECT to go nuts (buy the wrong ECT,?) no name or pn. stated. so...

my guess is that if the gauge does drop , with heater on max
then the cooling system does have issues.
is it full of 50% AF?
take of cap of rad, dead cold
is it full
and at the next hot to cold cycle? is it?

Jul 21, 2015 | 2004 Jeep Grand Cherokee

1 Answer

Find the actual temperature at the thermostat from my cell phone?

You don't say what kind of phone you have, but assuming it's an Android or Apple smartphone, you should understand a few things. First, your phone won't read outside temperatures by itself. You can use weather apps that download reports from local weather towers in your area, but these won't tell you how warm your home is.

How can you measure the actual temperature in your environment? You can purchase an sensor attachment that you plug in to your phone, or you can buy a thermometer/thermostat that transmits data to an app on your phone. I'm familiar with the Nest, a mobile-controlled house thermostat that works with central AC systems. It comes with an iPhone/Android app that reports on temperatures and allows a huge degree of customization in your home AC settings, but it's very expensive at over $300. Westinghouse probably makes cheaper wireless models too, but these thermostats aren't worth the money if you have a wall heater or room AC.

Me, I bought a $15 instant-read digital food thermometer from and take temperature readings by pushing it's on button. Cheaper, faster and easy.

Nov 18, 2014 | Cell Phones

1 Answer

Setting start temperature on central heating thermostat

It sounds like your heating system has to little capacity to heat the home properly. 21 degrees is a reasonable temperature to expect but if the unit is running all the time and can't reach 21 degrees the heater is too small.
As far as setting the thermostat here is a link to the instructions.

Nov 22, 2013 | Heating & Cooling

1 Answer

Humidity thermostat

I suspect the walls are warm and fooling the thermometers.

Aug 07, 2013 | Heating & Cooling

1 Answer

Where is the coolant bleeder on a 1998 ford taurus 3.0 engine

You can bleed the system of air by removing the radiator cap while the engine is cold. Turn the heater on high and let the vehicle run until it reaches operating temperature. The thermostat will open several times and purge the system of air. Feel the top radiator hose occasionally until it heats up. Don't forget to replace the radiator cap.

Jan 02, 2013 | 1999 Ford Taurus

1 Answer

A/c recharge what is thew psi for refrigerant

Below are normal car AC pressure readings with 134A.

Normal readings on high and low side with AC OFF (static pressure) – Depends on outside temperature, but normally is between 80-105 PSI

Normal low side reading with AC on high speed and MAX & engine at 800-1000 RPM’s – Ranges from 25-35 PSI

Normal high side reading ranges from 200-350 PSI
Don’t assume that if adding little Freon is good that adding a lot is better! Overcharging just a little can decrease the performance of the system and possibly damage the compressor.

With the AC on the coldest setting, use a thermometer in a middle vent. Normal vent temperature readings will vary depending on the (ambient) outside temp. The vent temperature should range from around 42-55 degrees in my experience.

If normal gauge readings are obtained and the vent air is cold – STOP don’t overcharge the system. The only proper way to remove refrigerant is with a AC recovery machine so if this is being done at home I can’t emphasize enough not to over charge the system.

Thank you for using fixya and be safe.

Jun 17, 2010 | 2002 Ford Expedition

1 Answer

When i was fixed a problem in central ac trane i found decreased in freon r22 and the suctione line was freezed, i charged the ac with froen gas r 22 then i found that the suctione line changed and begin...

You are still low on freon. Charging AC by superheat and subcool
First charging a unit by superheat, this is only for Acs with an orifice or capillary tube.
Optimum superheat is 12° to 15° at the compressor or suction line outside the unit.
Hook up your gages and put a thermometer on suction line (large line), start the AC. Measure the temperature of the suction line and read the pressure on your gages. Theres a temperature scale on your gages for R-22 or R-410A the needle will show you the pressure on the outer scale and if you follow it down to the R-22 or R-410a inner scale that is the saturation temperature for that refrigerant, (you can also use a temperature pressure chart), now read the thermometer, let’s say the suction temperature( the thermometer) is 67° and the saturation temperature (the gages or temp. press. Chart), is 55°, subtract the saturation temperature from the suction temperature, 67°- 55° = 12° superheat.
Charging by Subcooling, this is for Acs with a thermostatic expansion valve, it’s common to see a sight glass on the liquid line (on these units with a sight glass just clear it, when, indoor room is at approximate set point of the thermostat). Optimum sub cooling is 12° to 15° at the outdoor unit.
Hook up your gages and put a thermometer on liquid line (small line), start the AC. Measure the temperature of the liquid line and read the pressure on your gages. Theres a temperature scale on your gages for R-22 or R-410A the needle will show you the pressure on the outer scale and if you follow it down to the R-22 or R-410a inner scale that is the saturation temperature for that refrigerant,(you can also use a temperature pressure chart), now read the thermometer, let’s say the liquid temperature( the thermometer) is 100° and the saturation temperature (the gages or temp. press. Chart), is 114°, subtract the liquid temperature from the saturation temperature, 114°- 100° = 14° subcool.

Oct 05, 2009 | Heating & Cooling

1 Answer

My refrigerator constantly runs and is not cold enough. Could it be the control temp?

  • Freezer fan and its circuit problem.
  • Defective fan motor.
  • Defective defrost timer,defrost heater or defrost terminal thermostat.
  • Temperature control failure.
  • Compressor motor defective. Inefficient compressor (low wattage readings).
  • Condenser fan.AC circuit to fan open (high wattage reading). Defective fan (high wattage reading).

Aug 19, 2009 | GE Refrigerators

1 Answer

1997 Subaru Outback with temperarure problems

check the coolant level - you may have low coolant, causing the sensor to occasionally read an air pocket. If you don't correct this you will burn out your motor.
We had this problem & eventually replaced both the thermostat and radiator cap, being careful to bleed out any air pockets by running the engine form cold with the heater on hot and the radiator cap off - keep watching & topping up the coolant as the enigine heats & the thermostat opens.
Good luck!

Oct 26, 2008 | 1997 Subaru Outback

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