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I need to adjust the limit switch on a Lennox heat pump. How to I turn off power to unit before I open the control cover?

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If you mean the ambient lockout switch it shpopuld be oin the outside unit and all that you will need to shut off is the outside condenser before you open the panel. ther is a disconnect that you will have to throw either right by the unit or inside of a main breaker panel.. Hope that this helps and Thanks for using Fixya

Posted on Dec 25, 2008

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Posted on Jan 02, 2017

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2 Answers

Lennox rooftop Prodigy M2 controller is throwing code 61 witch is heat 2 limit open S99 what do you think the cause would be


dirty filter, bad fan motor, poor airflow, faulty limit switch, faulty prodigy. start simple

If you need further help, reach me via phone at https://www.6ya.com/expert/thomas_092728000e6acb79

Jan 12, 2018 | Heating & Cooling

1 Answer

THERMOSTAT CALLS FOR HEAT, WILL NOT COME ON, TAKE COVER OFF AND PUSH IN POP OUT BUTTON, AND WILL RUN UNTIL HEAT IS TO TEMP. WILL NOT TURN BACK AGAIN


When you take the cover off, you are turning power off to the unit. What this is doing is causing a reset to happen. Soumnds like you have a control problem on the unit. Could be a limit switch or safety switch.

Jan 28, 2016 | Heating & Cooling

1 Answer

Lennox ac stops working after normal shutoff untill i shut off power to air handler turn power back on ac runs till nornal temp reached shuts off will not come back on untill i kill power to air handler...


The 13HPX is a Heat Pump. It has a control board in the outside unit that will lock out after a few trips from one of the controls, such as a low or high pressure switch tripping. Turning the power off is making this board reset. Take the door off next time. to the outside unit and look at the lights on the control board. There should a sticker on the inside the door that you have to remove that describes why the unit is hard locking out according to the light configuration.

Oct 24, 2017 | Heating & Cooling

1 Answer

Lennox troubleshooting


The limit switches operate the fan relay. check them both for operation. one of them is bad.

Sep 16, 2017 | Heating & Cooling

1 Answer

Reset limiter switch on Lennox g10 furnace


Try turning the power off to the unit sometimes this works

Mar 05, 2012 | Heating & Cooling

1 Answer

My Lennox G10R03-110-1 heat unit, will not light the burners even though the pilot light is lit, and the thermocoupler was just replaced today


Hi,
You have a pretty old Lennox there. The G-10's went out of production many years ago....
Since you have pilot and the thermocouple was replaced you will need to check and see if there is voltage going to the gas valve. You should have 24v AC across the two wires on the gas valve when there is a call for heat. If not then the limit switch or the high limit switch are cutting the power to the gas valve. You will need to reset or replace them.
If you have power to the gas valve then you have a
faulty gas valve and will need to replace that.
It if very possible that the gas valve has failed on a furnace the age of yours. That would be my first guess. But do check for voltage before replacing it.

I hope that this will help you to solve your problem!

Thanks for using Fixya!!

Heatman101

Nov 29, 2009 | Heating & Cooling

1 Answer

Blower motor wont shut off


Turn the fan to the off position on the tstat. You colud have a ilimit switch or a relay on the control board if it has one.

Mar 23, 2009 | Heating & Cooling

1 Answer

Main limit switch


I am providing some information, but I encourage you to have a furnace technician look at your furnace. The reason is; the limit switch trips when there is a problem that may present a fire or combustion hazard. I've seen these switches go bad, but not very often. Usually they are tripping because the plenum is sooted up and excessive heat builds in the combustion chamber. This is common in older furnaces that have pilot flames- the flame runs all year and soot deposits in the plenum, plugging the air flow through the combustion chamber after years of use.

The limit switch is a safety control switch located on the furnace just below the plenum. If the plenum gets too hot, the limit switch shuts off the burner. It also shuts off the blower when the temperature drops to a certain level after the burner has shut off. If the blower runs continuously, either the blower control on the thermostat has been set to the ON position or the limit control switch needs adjustment. Check the thermostat first. If the blower control has been set to ON, change it to AUTO; if the blower control is already on AUTO, the limit switch needs adjusting.

To adjust the switch, remove the control's cover. Under it is a toothed dial with one side marked LIMIT; don't touch this side. The other side of the control is marked FAN. There are two pointers on the fan side; the blower goes on at the upper pointer setting and turns off at the lower pointer setting. The pointers should be set about 25 degrees apart. Set the upper pointer at about 115 degrees Fahrenheit and the lower one at about 90 degrees Fahrenheit.

Mar 15, 2009 | Heating & Cooling

1 Answer

Fan will not turn off


You should have a power disconnect within 10 ft of the unit.

Follow the high voltage power wire. The box you are looking for is typically gray brown or black, has a small door that flips up, and either a pull out switch or a breaker style switch inside.

They are usually mounted on the wall of the house near the unit.

Sometimes they are found in an outdoor panel box near the meter. Those are breakers.

Always test for power after turning it off just to be sure.

Dec 25, 2008 | Heating & Cooling

2 Answers

Air Conditioner malfunction


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. kstfas

Sep 23, 2007 | Heating & Cooling

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