I live in 1986 mobile home, when I moved in 3 yrs ago the air conditioner stuck running and kept getting colder until you shut it off at the furnace, I never know when it's going to stick, the coldest it has gotten was 58 that was when I woke up in the morning, I'm always afraid to leave for to long in case it sticks. It had the old round thermostat so my dad replaced it with a new programable one, it's still doing the same thing. I needed to get a new a-coil and replaced the part on the condensing unit a month ago. I only have 2 wires from the thermostat to the furnace, can someone please help me out with what needs to be done. Thanks so much
Air conditioner sticks and continuously gets colder
- Thread starter 2tzumom
- Start date
Users who are viewing this thread
Jadnashua
Retired Defense Industry Engineer xxx
Two things come to mind, and there may be others. TO turn on the a/c unit, all the thermostat does is connect the two wires together. IF they are shorted together anywhere along the way, in the wall, or who knows, that will do it. In a trailer, they can flex a bit, and that may only be intermittent, which may be why it doesn't do it all of the time.
The second thing is that the relay or contactor those two thermostat wires control could be sticking. Well, a third thing, someone could have been sloppy when wiring it up, and the wires around the screw contacts may be too long and maybe shorting the two control lines, simulating the thermostat closing.
A close inspection at the a/c unit might find the problem. You might consider just running a new cable from the thermostat and be careful of the routing and staples or clips you use...getting one of those too tight can give issues as they are metal, and can short the two wires...the insulation is decent, but not impervious to damage.
IN summary...there's 24vac on one lead to the thermostat...when it calls for cooling, it connects that 24vac to the other wire which goes to a relay (contactor) in the a/c unit which applies the 240vac to make it turn on. So there are really only two things that will keep it running: the 24vac is constantly being applied to the a/c unit to turn it on, or that relay is sticking. Sometimes, just a spray with some electrical contact cleaner can fix a sticky contactor. On mine, over the winter one year, a mouse electrocuted itself across the a/c power contactor. By the spring, it was all dried out, but it took a lot of cleaning to get the contactor to freely move as it should. In that instance, it was stuck open, and it wouldn't turn on, but it could happen the other way, too. Insects, and who knows what can mess it up. They're sealed, but not perfect.
The second thing is that the relay or contactor those two thermostat wires control could be sticking. Well, a third thing, someone could have been sloppy when wiring it up, and the wires around the screw contacts may be too long and maybe shorting the two control lines, simulating the thermostat closing.
A close inspection at the a/c unit might find the problem. You might consider just running a new cable from the thermostat and be careful of the routing and staples or clips you use...getting one of those too tight can give issues as they are metal, and can short the two wires...the insulation is decent, but not impervious to damage.
IN summary...there's 24vac on one lead to the thermostat...when it calls for cooling, it connects that 24vac to the other wire which goes to a relay (contactor) in the a/c unit which applies the 240vac to make it turn on. So there are really only two things that will keep it running: the 24vac is constantly being applied to the a/c unit to turn it on, or that relay is sticking. Sometimes, just a spray with some electrical contact cleaner can fix a sticky contactor. On mine, over the winter one year, a mouse electrocuted itself across the a/c power contactor. By the spring, it was all dried out, but it took a lot of cleaning to get the contactor to freely move as it should. In that instance, it was stuck open, and it wouldn't turn on, but it could happen the other way, too. Insects, and who knows what can mess it up. They're sealed, but not perfect.
Sponsor
Paid Advertisement
Tom Sawyer
In the Trades
The contractor at the compressor is bad or, you have an intermittent short in the low voltage wires that go to it.
WorthFlorida
Clinical Trail on a Cancer Drug Started 1/31/24. ☹
With only two wires you have an air conditioner only. Four wires would be required for A/C and Heat. No matter what type of unit you have there are two relays, one for the fan motor for the evaporator and the other for the compressor. Continuous running means that the controls (thermostat or wiring) has something wrong thereby keeping the relays energized. It is possible that one motor is used with a double shaft where one end has fan or drum for the air inside the home and the other end runs the fan for the condenser coils. Lastly, if you have a a 110 volt system, similar to a window air conditioner, there is one relay (double pole). One set of contacts is the the fan and the other contacts is for the compressor. But how do you turn it off?
Last edited:
