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Tell me exactly what is going on and what you mean C unit will stay on. Does indoor shut off but outdoor keep running or what?
OK so thermostat is not ever reaching the temp you ask for, but unit (both inside and out run nonstop)?
OK outside is going off before the thermostat temp comes down
OK .That points us to an issue with the outdoor unit. Here are a few things that may be the cause.
1,Outdoor fan shutting down causing pressures to rise and shut off compressor
2.Restriction in refrigerant line
3.Improper refrigerant charge
4.Compressor windings opening.
So Lets start with the outdoor fan. Does the outdoor fan stop before the compressor or do both fan outside and compressor quit at same time?
OK do you have to ret breaker or do both comeback on after awhile?
OK lets next look at the most obvious that will not require tools. Take a look in your main drain line (PVC) and see if maybe there is a float switch.Often a drain will become partially blocked backing up and causing float switch to kill signal to outdoor unit.As water seeps out, float switch closes and allows outdoor to come back on. See below
OK from here we need a meter to check when unit shuts off to see if we are losing the 24v at contactors and if so tracing to find where we are losing it.If you don't have a meter
You can get an inexpensive one at Walmart for about 15 bucks if you would like to troubleshoot and I would be happy to guide you.
OK is unit currently off with thermostat calling for cool to be on?
In the outdoor unit you will find a set of contactors. We should have 230v into the contactor 24 v to col on side of contactor and 230v out of contactor when thermostat is calling for COOl.
I will type up a list of what to check and you can come back when you get a chance if you would like.
1. Check the 230 volts into contactor
2.Check the 230 v out of contactor
3.Check the 24v to contactor coil
4.Check for 24 volts between the two wires (R and C) from thermostat where they first enter the outdoor unit.
5.Check at the indoor unit where wires leave going outside for 24v between those 2 control wires
6.Go to thermostat and put a jumper from R to Y and see if outdoor comes on.
If you can check each of these in this order and let me now results that will help me assist in determining problem.
I will attach a few photos to help you.
We can go from here
Wires where they enter unit