I turn the thermostat on and the heat kicks on for about 3 minutes then the air turns cold and the fan stays on constantly.termostat is set on auto,heat.Why wont it shut off when the heat shuts off. [arcoaire]
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Re: arcoair central heat /air conditioning unit
The blower motor kicks on when there has been a 24 volt control failure.
This usually means that a limit switch has tripped.
Most likely that would be a high temp limit switch or a rollout switch.
First, make sure the filters are clean. and the evap coil is clean. If eaither are dirty/clogged, it will partially block airflow, causing the furnace to overheat, causing the high temp limit to trip.
A rollout switch typically trips for three reasons.
1 flame rollout into the burner compartment due to poor airflow.
2 overheating af teh metal plate the rollout is mounted to, due to dirty, old, rusted components.
3 a bad limit switch.
If your unit has an LED light, count the flashes and it will hepl popint out the problem.
(locate the wiring diagram/flash code list, and correspond the flash count, with the code.)
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Sounds like the thermostat, the way to verify is to unplug indoor unit, remove thermostat, take pic of wiring with phone or label the wires as to the terminals. Carefully twist the yellow,(Y) Red (R) and the green (G) together. Plug the furnace back in, if the unit operates normally, replace the thermostat. I am basing this on the fact that the blower speed is changing. This could also be an anomaly within the circuit board in the furnace section, not likely though as the outside unit (condenser) is not controlled n by the indoor board unless this is a heat pump. hope this helps. D
Typical systems are designed with a thermostatic "fan limit switch" which protrudes into the heater (house air portion of the passages). The "fan limit switch" is mounted to, and protrudes into the duct within the burner section of the heater, near the heated metal.
This switch triggers the circulating fan to turn on only after the sensor (thus air) within the duct has reached well above ambient temperature. This design prevents the fan from coming on sooner and the system blowing cold air, which people don't like.
Depending on system design, installation and current operating conditions, the time delay from main burners on to fan on can be up to a couple of minutes.
This same limit switch, if the temperature goes high enough, will also turn the gas valve off; a fire safety function.
These heaters are the same as the marley heater, the element never gets red hot. the unit is set up so the fan kicks on after the element has heated to a certain temp and turns off after the element has cooled. It is common for these heater fans to cycle on and off quite often untill the air temp reaches about 55 degrees and then will operate normaly. If the fan still cycles too often you may have to replace the fan control and high limit switch. These are not very expensive and easy to replace yourself. they arte usualy attached to the back of the element with clips. The luke warm air is what these units put out. I have an equivelent to the dayton G73 and it heats a 24' X 30' garrage all winter in central Minnesota.
every single component in your cooling unit is needed for it to work, so anything can shut it down. If you could provide more information as to what type of unit you have: is it a central heat and air package unit? or central split system (furnace indoors and condenser outside)? or a wall a/c? Does any part of the system/unit do anything?
Hi, Sounds like you have a short in the control circuit to me. Turn off all power going to the unit. Write down or otherwise mark the wires leaving the control board going to the thermostat. Remove them from the control board. Replace the fuse. Turn power back on and see if the fan still runs. If it does, check and or replace the heat limit switch that brings the fan on during the heat cycle. It may just need adjusted. If the fuse blows, I would think that the control board is probably bad. If it doesn't blow, Remove the thermostat. Leaving all thermostat wires open check them with an Ohm meter. There should be no continuity between them. Twist all the wires together at one end and ohm them again at the other end. You should have complete continuity on all wires. If the wiring checks out, down power the unit. Double check your wire colors and rewire the control board. With all wires open at the thermostat, turn the power back on. Touch the RED wire to the YELLOW wire. The Condensing unit should come on. Touch the RED wire to the GREEN wire. The fan should come on. Touch the RED wire to the WHITE wire. The heat should come on. Down power the unit. Replace the thermostat. Test unit. If the fuse has lasted ok but blows now it is either wired wrong at the Thermostat or the thermostat is bad. I hope I have helped. NOTE: If you can not understand these instructions. Call a licensed Heating / Air conditioning company.