The thermostat may not be the problem. It may be inaccurate regards to the setpoint vs. actual room temp ... i.e. setting at 65°F to get 72°F room temp (at night) ... but if that is consistent operation, it cools to 72°F and then cycles off/on to maintain 72°F, then the thermostat is not the problem regards to the room temp running 5°F to 8°F higher during (the heat of) the day.

Or, does it run continuously at night to maintain 72°F? If so, does it cycle off if you turn the thermostat to 72°F when that's the room temp? Have you verified 72°F room temp with a separate thermometer?

Any air conditioning system can remove no more than a specific amount of heat per its rated capacity (BTUs per hour). Inability to handle the cooling load could be caused by dirty/clogged (indoor) cooling coils and/or outdoor (condensor) coils, dirty filter, low on refrigerant, or simply undersized.

I have an indoor temperature gauge, and a surprisingly accurate digital meat thermometer. It does not run continuously, it cycles on and off. If it is running and I move the thermostat up it cycles off immediately. It doesn't just run higher during the day, it runs consistently higher all day and night. The manager is trying to use heat as an excuse as to why it is hotter. but wouldn't it just be hotter in the day and cool correctly at night as the strain of the heat is removed?

For instance currently I have it at about 70 and it is 75.

They are supposed to clean the coils when they replace the thermostat, so hopefully that will help it cool more efficiently.

Does your apartment have any insulation? Are you on the topmost floor?

If it can't get the temperature in your apartment down to the thermostat setpoint then it's not working (aka "broken")! I doubt the thermostat is the problem. If cleaning the coil doesn't do the trick then they need to get a professional company out to diagnose and fix the problem, or replace the AC.

I would think that would be the case, but I was told, "we don't really replace the ac if its not completely broken." Translation, this is the last thing they will do, if that doesn't fix it, then oh well.

I called a company in the area just to ask, but they said that 4 degrees isn't really that big of a deal. I said yeah, its when it gets up to 7 degrees higher is when I have the problem. She said with an older unit that it is what it is.

I really hope it works, but if it doesn't and they tell me to suck it up, I don't know what I can and can't demand they do. I know after three written maintenance requests I can break a lease if they don't fix something, but I don't know if them trying and stopping just short of replacing the ancient thing because its still working well enough is a good enough reason to break a lease without bring charged.

I am on the top floor, Im sure it has insulation, but I don't know. The area where I live gets about 75 at night, that is where I really have problems with it not wanting to get cool. That and paying for it to be 65 all night when it is anywhere from 70-73.

It could be the thermostat is old and is no longer accurate. You can use your temperature gauge for the measurement.

The supply temperature should be 55-60 degrees. If it is not then the AC needs to be serviced. Cleaning the coils is not going to do it. Most likely it is low on refrigerant. The system is running inefficiently which is causing your high electric bill.

Find out if the service tech has measured the refrigerant level when he come out to clean the coil.

There should be a 12°F to 16°F drop in temperature between the intake (room air) and outflow (after the system cools it). The specific outflow temperature at any given moment depends on what is the intake temperature. Intake air of 85°F won't result in 55°F outflow, that's a drop of 30°F.

"Old-style" mercury-bulb thermostats depend on being level for accuracy. Not unusual, particularly in an rental apartment, that they're not level. They also have a small internal heating device (called an anticipator) which can fail after years and cause inaccuracy or a larger differential (the temperature difference between turn-on and turn-off cycling).

The history of operational characteristics also is relevant to determine if there is a problem, or if the situation is related to hotter-than-usual weather. Has the system always had a bit of trouble maintaining the desired room temperature during "heat waves" or is this a new problem?

I know they have added Freon, I’m assuming he measured what the system needed. When he added it worked perfectly until during the night it dropped back to the 5-7 degree difference.

I have no idea. I moved in halfway through August. And noticed that it was really hot. Especially in my room which is weird because right next to my door is where the compressor is located. i Looked up my roommates previous bills, and talked to some people who have lived in the area, and they’re high.

"Old-style" mercury-bulb thermostats depend on being level for accuracy. "

Say what? Nope.

SaltiDawg,

So a thermostat like this, which depends on a capsule of mercury tipping across a balance point to turn the system on or off ...

isn't affected by mounting it on the wall off-level like this

A rental unit, whether it be an apartment a house a town home or condo makes really no difference.

The landlord (most of them) are for the lack of a better term 'bean counters'.

The interest of the landlord is profit and the cost of HVAC replacement is in most cases one of if not the most expensive when it comes to a rental operation.

In some cases the skill of those that work for the landlord can also be questionable. Realize whatever the landlord 'pays for' the result of that is how much less 'profit' the landlord will make.

I am also a landlord in a very hot climate, so my thinking is different. Because I know of another high cost problem when it comes to rental units and that is 'turnover'. This means tenants move in and move out on a continual basis.

Regardless of what I put here there will always be landlords that do things as you are experiencing them. The other part of this problem is debt load of the landlord in question. A common theme among landlords is to mortgage the places they own to the hilt so they can go out and buy more rentals. (It's a double edged sword).

So the profit they make from any one property after all expenses may be as little as $200 per month. This could be the reason among possibly others as to why and how this situation won't be resolved to your liking.

If your unit took Freon, it has a leak and so how long this charge will last could be a few weeks to a month or two, or best case a year. The landlord rarely pays the utility bill of a rental, so there is no real incentive for them to replace the equipment except to cut turn over of the rental.

I service the Katy, Texas area.