Unit shuts off and will not come back on

The question is: it not shutting off because of a the switch or is it because it does not get cold enough. Do a test. Put a thermometer inside the freezer and leave it for an hour or more. then quickly read the temperature. The freezer should be about 25 deg. If it is not that cold, it means the compressor is not cooling. In that case, try cleaning the condenser coils in back with a vacuum cleaner or brush. If the freezer gets too cold then it is the thermostat.

May be a faulty thermostat. Try bypassing the t-stat, if the unit keeps running normally, the stat is bad.

did you set dip switchs on new stat for ht pump with electric ht back up if that is your type of heat. newer t stats might not have dip switchs but a sequence of programing steps to set up new stat to match your needs ps when set up correctly the fan will run for a few minutes after cycle over to discharge residual heat from unit n ducts .

My first guess is a dirty outdoor coil would give same symptoms you are having, high head pressure caused by the lack of air flow thru the coil, preventing proper heat rejection.

the stat has a range of 50 to 90 degrees, put the copper bulb on the back bottom of unit in cold water, if unit comes on the thermostat is bad.

the first problem is you need a milli-volt t-stat and your central has a 24volt t-stat if you connect the 2 it will fry the controlls in the wall heater the second problem is t-stat location if the wall heater is near the central heats t-stat it will shut off the central to soon . maybe relocate wall unit to coldest room ?

first thing you need to check is if the reversing valve is working you maybe running your A/C with the heat strips on depends on the t-stat your using some heat pumps will bring the strips on with a high degree difference in setting and room temp .

1- turn t-stat to heat set temp 10 degrees above room temp if you have a programable t-stat it will have a time delay on it allow to for the outdoor unit to come on 2 to 5 minute usually .
2- walk around to the outdoor unit when it comes on feel the big line the insulated one and see if it is hot or cold let it run for a 5 minutes peel back the insulation and gently grab the line with your hand it maybe real hot so be careful if this line is hot then your heat pumps is working mechanically and if it is just warm then you may need the charge topped off

there are so many different option's from this point i will need to know the findings of this test first thanks : Michael

Hi, the only thing that could cause this to happen would be the thermostat. This is the main part that controls the roof top unit, getting its signal from the stat to come on and maintain the correct temperature. I would replace it with the same type and this will solve your problem. The only other thing that would cause any unit to cycle like this is if you had bad thermostat wiring touching together some where. I don't think this is the problem with yours though. With the stat off and it still cycles on, this tells me for sure it is the stat. Change it out and you will be good again.
Sincerely,
Shastalaker7

it will take some times depends on ambient temp
but the probleme is to avoid freezing
-1 clean the a/c mainly (evaporator) clean air filter
-2 check and set your thermostat
if not cheak for leak of freon and recharge

Sounds like a stat problem, is it running all the time or does it shut off, put something warm on the stat if it comes on its the stat