Lennox mini split troubleshooting

HVAC Logo IconBy HVAC.comAugust 1, 2023
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If your mini-split isn’t working right, these Lennox mini split troubleshooting tips might help you fix it yourself. Of course, if you aren’t comfortable performing these tasks, call a certified HVAC pro. They can help you get your mini split back in shape. 

Lennox mini split is dripping water or not draining properly

First, check your air filters. You should clean these every few months. Dusty filters can cause a host of issues with your HVAC system because of reduced airflow.

Open your evaporator (the indoor cabinet) and remove the air filter. You can rinse it in the sink, or vacuum it with a hose attachment. When it’s clean, return it to the evaporator.

Mini splits remove moisture from the air, so there may be some condensation at your heat pump. But if it’s making a puddle, you have a problem. Some models do have a drain pan under the heat pump that collects condensation. It may be overflowing because of mold or debris.

Turn the power to your heat pump off at the circuit breaker. Clean out the drain pan with an old towel. Open the unit (you may need to unscrew the cover with a screwdriver). Look for clear tubing inside. If you see a visible clog or mold in the tube, use a shop vac to suck it out. Alternatively, you can remove the tubing and use your garden hose to clean it out before replacing it. 

If these Lennox mini split troubleshooting tips don’t work, call a technician. Your issue requires professional attention.

Lennox mini split is not heating or cooling

Check your thermostat. Set it at your desired temperature. Choose “cool” if you want AC or “heat” if you want heat. Put it on “auto” instead of “on.” If you choose “on,” the mini split will blow air when it’s not actively heating or cooling.

Go around your home and feel for air leaks. If you feel a draft, especially near a window or door, seal it with weatherstripping tape. Your mini split may be working but unable to keep up if the cool/warm air is escaping. 

Check the air filters. They may be dirty, blocking cool/warm air from entering the home. Open your indoor evaporator and remove the air filter. Vacuum it with your hose attachment or rinse it in the sink. You can purchase a replacement on Amazon – just be sure it’s the right size and compatible with your model. 

Call a professional if these Lennox mini split troubleshooting tips don’t help. It’s likely your refrigerant is leaking. If this is the case, the coils (metal tubing that zigzags inside your heat pump) may appear frozen.

Lennox mini-split is making unusual noises

Identify where the noise is coming from.

If you hear popping or clicking coming from your evaporator (indoor cabinet), it may just be the plastic cabinet expanding during use. No need to troubleshoot – this is normal.

Check the air filter if you hear a whistling sound coming from the evaporator. Pop it out and clean it. Vacuum it with a hose attachment or rinse it in the sink. Make sure you dry it thoroughly before putting it back.

If you hear gurgling or crackling coming from the heat pump (outdoor unit), it may be turning on defrost mode. This is part of its normal operation. 

If you hear clanking or jangling from the heat pump, turn off the power and remove the cover. You may need to unscrew it with a screwdriver. Check inside for any loose debris. If sticks, rocks, or leaves are inside, clean them out. Check for screws or bolts that have fallen inside. Make sure any visible screws are tight and holding the components in place.

If these tasks don’t alleviate the noise, or if you hear a more jarring noise like screeching or banging, call a professional for help.

Lennox mini-split has a strange smell

If your home smells of mildew, it’s possible the cause is your mini split. If mini splits aren’t cleaned regularly, they may not drain condensation properly. This excess moisture causes mold. The Environmental Protection Agency suggests calling an HVAC professional to handle mold removal properly. Check your owner’s manual for cleaning instructions. 

You may have a refrigerant leak if you detect a smell like vinegar or nail polish remover coming from your mini split. Call a technician. They can repair the leak and refill the refrigerant.

If you smell burning or an “electrical” scent coming from your unit, you may have wiring issues or a failing motor. This isn’t a DIY job – call an HVAC pro.

With any of these smells, it’s best to turn your mini split off until you can give it proper attention. You don’t want a mold odor spreading through your home. And you don’t want to further damage your system.

Lennox mini split troubleshooting resources

Lennox has a troubleshooting tool to help identify and fix issues with your system. Its site also has a product literature lookup, where you can find the owner’s manual for your model. These Lennox mini split troubleshooting resources may help you identify parts and determine whether you need to call a pro to fix your issue. 

If you’ve tried our Lennox mini split troubleshooting suggestions and still need help, reach out to a certified HVAC professional. A technician can also perform troubleshooting for you if you prefer not to do it yourself.

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