central heating unit kicking off and on?

Question

i just turned my central heating unit on last night for the first time this season and not long after i turned it on i kept hearing it kicking off.........kicking on.........kicking off.........kicking on..........like 5 seconds on then it kicks off waits about 5 seconds then kicks on.........anyone know what the problem is?
thanks
oh and yes i turned it off

Answer 1

Could be a bad heat sequencer or a bad fan relay. Hard to judge this one without seeing it. Could even be that the fan isnt coming on and the heat is kicking off with the high limit switch

Forgot to add this, If its a gas furnace, Then its the Fan switch

Answer 2

Just by what you are explaining its sounds like the unit is going off on limit which is a condition in which the furnace is operating at above normal temperatures as I will explain. Furnaces are designed to operate at a specific operating temp and this is achieved by maintaining a certain amount of cfm or airflow going through the unit. So when this cfm or air flow is restricted it can make the inside cabinet (where the heat exchanger is located) run at a hotter temp which trips the safety limit switch to prevent damage to the unit thus shutting the unit down until it cools, When the unit cools the unit will cycle and fire up and will trip on limit again, and this process will continue until the unit is serviced by a tech. So since the unit does not take long to overheat and trip the limit the furnace never runs long enough to get any heat out of it to satisfy the thermostat temp you have set as the desired temp for the home and this condition is known as short cycling. So we need to start from the basics and check some simple things to figure out what is causing this unit to overheat and trip limit. 1) Check to make sure your return vents either on the floor or wall ar not blocked or obstructed. 2) Make sure within a couple of minutes ( 2-3 ) after the burners ignite the blower motor should turn on and heat should flow out of the vents. If the unit shuts off within a couple minutes after the blower kick on. Some things a tech should check is that there is no obstruction in the exhaust pipe going to chimney like a dead bird or nest because if it is a newer unit it will have a inducer motor above the burners. That inducer motor helps remove the exhaust gas out of the unit and it has a plastic vacuum line that is connected to a vacuum controlled switch. If their is no obstruction in the vent pipe leading to the chimney their will be a vacuum created in this vacuum line from the inducer which will close the vacuum switch and allowing the furnace to fire. However is their is little or no vacuum it will cause the furnace to shut down. So 1) Check to make sure their no blockage in chimney or piping 2) Remove the vacuum line where it attaches and make sure a spider has not spun a web in the orifice where the vacuum lines which will cause a weak vacuum. ( I pulled my hair out on a unit for a couple hours and that's what the problem was) Ok if we pass those test the other thing to check is to make sure the "A" coil is not clogged up with lint. If you have central air there is a coil that sits on top of the furnace and sometimes when the furnace is ran without a filter the A coil becomes the filter and will trap lint like the dryer after you have dried a load of laundry. Well when you get lint and dirt built up heavy enough it cause a obstruction of air flow trying to get through it and causes the unit to run at a hotter temp and trip limit. This condition can be caused from using cheap see through filters but the biggest cause is when homeowners take out the filter with good intentions of putting a new one in and then they forget and 6 months later the A coil is clogged. I would also replace the limit switch cause sometimes when they are overheated they never work the same. So theses are some things I would look so ... Best of Luck !! Hopes this helps in some way ...

Answer 3

do u have a round thermostat with mercury inside??
make sure it is level on the wall
personally change it to a digital

is your heating system a high efficient 90+?
then it may have an air inlet pipe on the outside of the house
make sure it is not blocked with debry

Gas or Oil? if it is oil then get a technician over to check it

Answer 4

it sounds as though you don't have it high enough. Try starting out on 80, then turn it down to 70. If it doesn't work, you'll need to pay the expense of having it looked at. Sorry, if you own your own home. If you live in an apartment, call the landlord.

Answer 5

If it is electric ignition, check to see that it is turned on or that the ignitor coil heats up. If it is gas with a pilot light, make sure the pilot light is lit. Something similar has happened to me..

Answer 6

is the gas on?

are the combustion vents plugged?


anything more than that, call the repair man