Lennox heat pump troubleshooting

HVAC Logo IconBy Tom MoorAugust 1, 2023
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Lennox heat pump giving you trouble? You may be able to solve the problem yourself with our Lennox heat pump troubleshooting tips. We’ve listed simple fixes for some common issues below.

But if you’re not feeling up to the challenge, no worries! A skilled HVAC technician can identify the source of trouble and get your system working again. 

Don’t want to deal with DIY?

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Lennox heat pump is not turning on

First, check your thermostat. Make sure it’s set appropriately for the season. In summer, choose “cool.” In winter, choose “heat.” Set it to “on” instead of “auto.” Most heat pumps have a 5-minute time delay, so wait momentarily to see if that makes the heat pump start.

If the thermostat isn’t the problem, locate the defrost control board on the outdoor unit. The board will flash LED lights to signal different fault codes. Check to see if the board is flashing a code.

Next, check your electrical box to see if a circuit’s tripped. If it has, reset it. If it hasn’t, try turning the circuit to the heat pump off and back on.

If the fan on your compressor (the big outdoor unit) is working, turn your thermostat’s “emergency heat mode” on. Raise the temperature setting to two degrees above the current indoor temperature. Give it a few minutes. If it feels like heated air is coming out of your indoor registers, the issue is with your outdoor compressor. If you don’t feel warm air, the issue is likely with your thermostat or air handler (the indoor component that blows air through your ducts).

Armed with that information, call a professional for help. They can pinpoint the exact part that’s malfunctioning and repair or replace it.

lennox heat pump troubleshooting outdoor unit

Lennox heat pump is not blowing hot or cool air

Check the thermostat. Set it to the temperature you desire. If you want AC, select “cool.” If you want heat, select “heat.” If you set the mode to “on” instead of “auto,” the heat pump will blow air constantly, even when not actively heating or cooling.

Try the opposite of what you want – If your system isn’t cooling, set it to heat to see if that works, and vice versa. If it’s doing one thing and not the other, your reversing valve is likely stuck. Call a technician. Repairing this part is a job for an expert.

Check the coils on both your outdoor compressor and indoor air handler. You may need to use a screwdriver to remove the external covers. If the coils (the metal tubing that zigzags back and forth) look frozen, your problem is a refrigerant leak. Call a professional who can find the leak and replace the lost refrigerant.

If you can access your ductwork, look inside for blockages or holes, especially at joints in the ducts. You may be able to partially view your ducts by removing the registers from your vents and looking inside with a flashlight. If you find debris causing a clog, remove it. And if you see a hole, repair it with aluminum UL181 tape or sealant. If you can’t access your ductwork and you suspect that may be the problem, you can hire a duct cleaning service to ensure they’re in top condition.

Call an HVAC expert if these Lennox heat pump troubleshooting tips don’t help you pinpoint the problem. They can figure out what’s going on. 

Lennox heat pump is frozen

There are three common reasons your heat pump freezes: It’s cold out, the heat pump outdoor fan is broken, or the filter is restricting air flow. It’s possible that you could have a refrigerant leak, but a simpler explanation is more probable.

Heat pumps have a defrost cycle to melt frost on the outdoor unit. It should kick on automatically. If it hasn’t come on, you can turn it on manually. This process varies by model, so refer to your user’s manual for instructions.

Do not attempt to break away ice with a sharp object – this may damage the heat pump. If the defrost mode isn’t working, call an HVAC technician.

If your heat pump is frozen and it’s not because of the weather outside, call a professional to help. You likely have a refrigerant leak. Your technician can repair the leak and refill the refrigerant.

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Lennox heat pump is making noises

If you hear a whistling sound inside when your air handler is blowing, it may be coming from your ducts. If you think that’s the case, you probably have a leak in your ductwork. Call an air duct cleaning and repair company to service your ducts.

If you hear a rattling or clicking sound coming from your outdoor compressor or your inside air handler, turn off the circuit breaker associated with the unit. Remove the cover – you may need to unscrew it with a screwdriver. Wear protective gloves and feel around the unit to ensure there aren’t loose parts. Remove any debris inside, like sticks, leaves, rocks, or small toys. Check that all bolts and screws are in place and tightened. 

If you hear other noises, such as screeching, thumping, or humming, turn off your system so it’s not further damaged. Call an HVAC technician to see what’s up. You likely have a problem that’s not DIY-able.

Lennox heat pump troubleshooting resources

There’s a Lennox heat pump troubleshooting tool to help identify and fix issues with your system. Lennox also has a product literature look-up on its site, where you can find the owner’s manual for your model. These Lennox troubleshooting resources may help you identify parts  and determine whether your issue is a DIY fix or not. 

Our website also has a guide listing the most common heat pump problems and how to avoid them. It may give you more troubleshooting inspiration. 

If you’ve tried all our Lennox heat pump troubleshooting tips and still can’t solve the problem, consider calling a professional. A technician can also perform troubleshooting for you if you prefer not to do it yourself.

Click below to connect with a top-rated local HVAC technician who can get your Lennox heat pump back up and running! 

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