Ductless split-system air conditioner querstions & answers:

These questions & answers from readers help diagnose problems with split system or ductless air conditioner and heat pump systems.

This article series describes split system air conditioning & heat pump systems. We review the major system components, switches & controls, and typical applications for split system cooling systems.

Split System Air Conditioner & Heat Pump System Diagnostic FAQs

A split system or "ductless" air conditioning (or A/C & heat pump) system dispenses with duct work entirely, using a wall-mounted indoor evaporator/blower unit and a separate outside compressor/condenser.

These split system A/C install, troubleshoot, repair FAQs were posted originally at SPLIT SYSTEM AIR CONDITIONERS & HEAT PUMPS - home - be sure to see that article.

Question: minisplit AC turns itself on and off at will intermittently

(Aug 4, 2014) Wayne said:

My minisplit AC turns itself on and off at will intermittently, but otherwise works very well for days. any suggestions

Reply:

Wayne,

Check out the diagnostics at inspectapedia.com/aircond/HVAC_Compressor_Hard_Start.php where we discuss intermittent AC operation under the aegis of hard-starting compressors.

Question: Tripping breakers on AC systems

(Aug 17, 2014) Anonymous said:

the united was running good,buy keep tripeing bracker,now theire is no cold air comeing out of united out side united feels like cool air out side now was hot air comeing out the fan earlily today

Reply:

Anon

Tripping breakers on AC systems often mean a compressor motor is failing.

Also check for wiring shorts or burn-up.

Question: we see large pieces of ice accumulated inside the wall mounted unit

(Sept 21, 2014) Deena said:

If we have our mini split on for 8 hours, we see large pieces of ice accumulated inside the wall mounted unit. The air output also seems to be weak. We have pulled the filters are cleaned them. Other than air output, we haven't noticed anything wrong with the unit. Any suggestions? Thank you.

Reply:

Ice accumulation can block air flow and thus reduce cooling effectiveness. On a cooling coil ice often means either a blocked dirty air filter on the return air side or low refrigerant.

Question: a heat pump stays in the defrost mode

(Oct 23, 2014) Anonymous said:

why does a heat pump stay in the defrost mode?

Reply:

Look for a stuck or failed relay or control board

Question:

(Oct 23, 2014) Freitas said:

Our Fujitsu inverter air conditionig/heat pump,works perfectly on cool mode. But when we changed to heat mode it takes about 5 min to start. Then ventilation is very low and cold.

After another 5 or 6 minutes the compressor stops as well as the inner ventilation. The "operation" green light remains still (no blinks), but the equipment won't start again. What can be happening?

Reply:

Freitas

Possibly there is a control board or relay problem, or the reversing valve is not operating. It's time for a service call. Keep us posted.

Question: Ruud split heating / air conditioning system not working

28 Oct 11 Anonymous said:

I have a Ruud split heating / air conditioning system. The unit outside will activate via thermostat control but the air handler in tha attic will not turn on and blow air. The breakers are not tripped. Any suggestions?

Reply:

Anon:

After confirming that the unit has power,
Check for a condensate trip tray overflow switch that has been activated.

Question: Fujitsu inverter air conditionig/heat pump not heating

(Nov 2, 2014) Freitas said:
Our Fujitsu inverter air conditionig/heat pump,works perfectly on cool mode. But when we changed to heat mode it takes about 5 min to start.

Then ventilation is very low and cold. After another 5 or 6 minutes the compressor stops as well as the inner ventilation. The "operation" green light remains still (no blinks), but the equipment won't start again. What can be happening?

Reply:

Freitas

Possibly there is a control board or relay problem, or the REVERSING VALVE on HEAT PUMPS is not operating. It's time for a service call. Keep us posted.

Question: short cycling ductless AC unit

(Nov 14, 2014) hmali said:
My aircon split ductless inside unit short cycling or on/off in heating , it work normal in cooling, out side compressor works normal only inside wall mounted air ventilation air keeps on/off any suggestions. Thanks

Reply:

Sounds like a control board or relay failure. I would turn the system off until it can be serviced.

Question: Electrolux Kelvinator AC unit won't cool

(Nov 15, 2014) Anonymous said:
why does the indacater Hi

(Nov 24, 2014) wendy said:
Our electrolux kelvinator kelvinator air conditioner won't turn to cool blows hot air all the time.do you have any suggestions thanks

Reply:

Wendy in the ARTICLE INDEX found at Continue Reading links above, the article titled

DIAGNOSTIC GUIDES A/C / HEAT PUMP

offers a sequence of things to check if an AC system won't turn on or won't blow cool air.

Question: Mitsubishi Split Mr. Slim (MSZ 12) system shows the 2nd (lower) operating light on

(Jan 24, 2015) Alan MacDonald said:
My Mitsubishi Split Mr. Slim (MSZ 12) system shows the 2nd (lower) operating light on at some times --- normally just the 1st (top) op light is on.

I suspect, but don't know (since the documentation doesn't say anything) that the 2nd light means it is in its 'defrost mode'. This happens infrequently and stays on for only a 5 or 10 minutes. At such times the unit seems to just blow air with little or no heat and vents turn up.

It seems to me that the behavior of the unit suggests it is in defrost mode, and thus that the 2nd light means "defrost on", eh?

Reply:

Defrost mode means the unit is turning on to melt ice accumulation, right? Sounds right. Ice blocked coils won't pass much air.

Question:

(Feb 17, 2015) Amy said:
We had a dual zone split system installed this summer, and all seemed well, until "heating" season. The temperature of the air coming our of the system is only able to keep the house at around 45-50 degrees F.

Technician is thinking maybe low Freon (unit is displaying no error codes on board outside, nor either unit inside).

The problem is that the mini split units don't have what he calls a "heat check valve", meaning he can't check the Freon level properly while system is in heat mode (gauges read RETARD), and it is too cold for the unit to switch to AC mode.

He is afraid to just add Freon, without gauging, because if he overfills, it would ruin compressor. Is there a workaround for this issue, or do mini splits have to remain useless hunks on the wall if they require repair during winter? Any help would be appreciated!

Reply:

Perhaps your backup heat is not working. That's where I'd start. A simple check with a VOM or DMM may be enough to see what's happening.

Question: Soleus air split unit not working

Apr 2, 2015) Ben said:
I have a Soleus air split unit. The digital control won't drop under 61 degrees. Can I bypass the temp control or thermistor and hook up a separate temp controller, something like a coolbot but not so expensive?

Reply:

Ben let's clarify the question first:

Are you saying that you cannot set the control below 61F - and that that bottom is specified in the control's design?

(Apr 3, 2015) Ben said:
Yes, that is the way its designed. It does not drop under 61

Reply:

Ben

IN that case before giving any thought to modifying or bypassing the control I'd look at:

1. the location of the remote sensor / controller that communicates with the wall-mounted indoor half of your system.

2. the instructions from the manufacturer: you may want to give them a call. If you set the low temperature lower than the manufacturer intended I expect that the unit may simply run continuously and you may be exceeding its design parameters. I'm not sure but that might in turn damage the equipment or void its warranty.

Question: installing a soft panel for a minisplit heat pump and a/c unit

(June 8, 2015) Nancy said:
Is there an advantage to installing a soft panel for a minisplit heat pump and a/c unit for an attached 340 sq. ft. room addition with a separate entrance that I am adding to my house?

Reply:

Sorry, I don't recognize "soft panel"

Question: Sanyo KS1872 iced up

(June 14, 2015) Frustrated said:
We have a Sanyo KS1872, it iced up on the inside and outside....we have been running it during the day and shutting if off at night time...we have a berm home and we have had problems every year since it has been installed with water dripping or pouring out of the inside unit down our walls etc...

Our installer has been here several times and first time he put some insulation in the wall, but still leaks, the last time he came he gave me a tube and told me to blow in it to unblock the drain...I am frustrated, any advice?

Reply:

Frust

If the cooling is icing up there is a problem with a refrigerant metering device or with the refrigerant charge or perhaps with a blocked air filter that has reduced air flow across the cooling coils.

When severe icing builds up and then melts it can overwhelm the drip tray and condensate drain or it may drip actually past the perimeters of the condensate catch pan.

Yes a blocked condensate drain can also be a problem. If you can pour water into the drain and it flows to outside the drain is not likely to be blocked.

Question:

24 June 2015 Anonymous said:
why does my KMS 1872 keep turning off by itsef. KMS1872 I have hanged batteries and also no longer put it on a timer as that didnt seem to work so I thought if I just put it on without a timer it would stay on but it does not. HELP PLEASE!!

Reply:

Check first for thermostat wires or control shorted internally

Question: Mitsubishi split system has always emitted an odd chemical smell when cooling

28 June 2015 Lynn Dow said:
One unit of three, in our 2 year old Mitsubishi split system has always emitted an odd chemical smell when cooling.

It has done this since new and in spite of professional cleaning/ servicing every 6 months. Yhe company service supervisor says he never heard of such a thing. ?

Reply:

Refrigerant is odorless. I'd look for an oil leak or a contaminant or mold in the air handler.

29 June 2015 Lynn Dow said:
Would the air handler be outside in the main motor condenser, or inside in the one (of three) units?

If this inside unit had the weird smell when it was brand new, could it still be contaminant or mold? I'll have the service tech look, but would like to have some clue as to what I'm talking about. This is a swell forum. Thank you.

The "air handler" in an air conditioning system is the indoor unit that cools and blows air into the occupied space.

I can't guess that a new outdoor unit would be moldy (anything's possible but that doesn't seem likely) - except to speculate that perhaps there was an oil on components that burned off when those parts heated up. If that's the cause, your tech should be able to use a suitable coil or equipment cleaner to reduce the complaint.

Question:

(June 29, 2015) Lynn Dow said:
Would the air handler be outside in the main motor condenser, or inside in the one (of three) units? If this inside unit had the weird smell when it was brand new, could it still be contaminant or mold?

I'll have the service tech look, but would like to have some clue as to what I'm talking about. This is a swell forum. Thank you.

Reply: Where is the air handler? What about mold in the outdoor air conditioner unit?

I can't guess that a new outdoor unit would be moldy (anything's possible but that doesn't seem likely) - except to speculate that perhaps there was an oil on components that burned off when those parts heated up

If that's the cause, your tech should be able to use a suitable coil or equipment cleaner to reduce the complaint.

Question: installer did not evacuate refrigerant lines; installer did not install proper refrigerant charge

7 July 2015 Greg H said:
Just purchased a new split system air conditioner.

1. Suspect installer did not evacuate the piping lines properly (if at all) before releasing the refrigerant into the system. What can I expect in terms of system performance and longevity?

2. Installer admitted he did not add additional refrigerant as specified by the manufacturer for long piping lines. This requirement is nil up to 10 metres and then 30 grams for each additional metre of which I have 3.

Again, what can I expect in terms of system performance and longevity?

Reply: effects of failure to evacuate referigeration lines during installation of an AC or heat pump

Greg,

1. Failure to evacuate referigeration lines during installation of an AC or heat pump:

if any new AC or heat pump system is installed with contaminants in the refrigeration piping system trouble may first show up as a clogging or misbehaving refrigerant metering device (Thermostatic expansion valve or TEV, or capillary tube or cap tube).

A result can be lost cooling or cooling coil icing or (perhaps less likely) liquid slugging of and destruction of a compressor motor.

It might take some time for contaminants to move through a system to the TEV or they may never ever appear there if they are captured by the filter/drier that is typically installed on such systems.

If you knew, rather than suspected, that the system were improperly installed you could call for the installation of a filter drier ahead of the compressor unit or on both high and low pressure sides of the system. That job requires cutting the refrigerant piping, thus system evacuation and re-charge. That means it's expensive

2. Insufficient refrigerant: most air conditioners larger than small window units include a receiver that includes a "buffer" quantity of refrigerant, so the system might work adequately even if some additional refrigerant could have been added during installation. Low refrigerant may show up as icing on the cooling coil and thus lost cooling ability of the system.

In some split systems were coil icing occurred I've seen water pouring out of the wall mounted air handler when the system was shut off and the ice melted, overwhelming the condensate drain system or dripping past the condensate catch tray.

Unlike adding a filter drier, adding refrigerant does not require cutting into the refrigerant piping system as split system AC units typically have both low pressure and high pressure side service valves at the outdoor compressor/condenser unit.

But the bottom line is that the manufacturer knows what is needed for their equipment to work properly both regarding line evacuation and refrigerant charge.

Check with the manufacturer, then give your service company's service manager a call and politely ask that the job be finished correctly.

Watch out: I'm presently working on a new InspectApedia article about adding refrigerant to split system AC units in which I describe further incomplete and sloppy work by the technician - a perfectly nice guy but a fellow who told us at the outset that he hated working on split system units.

We paid a small fortune for the insertion of an un-measured, unknown quantity of refrigerant into an older system that had a slow refrigerant leak.

At several InspectApedia articles we advise that it's best to find the leak rather than just keep adding refrigerant to an air conditioning or refrigeration system.

The technician's view was that finding and fixing a refrigerant leak was so expensive (more than $1,500. USD) that it's better to just give the system a re-charge. My view was that I could see oil around one of the service valves and that most likely that was the leak point that needed attention.

(July 7, 2015) Greg H said:
Thank you very much for your prompt response.

In respect of Item 1, sounds a bit like "contaminants" may mean things like particles, fluids, greases and such things. Does the air that has not been evacuated also have an affect in some way?

Reply:

Yes air changes the properties of a refrigerant depending on how much is mixed on. And besides particles, moisture could also be a contaminant . Filter driers may trap particles and moisture but not air mixed in with a refrigerant.

Question: Sanyo inverter 180 model sap-250vs

(July 18, 2015) Hesam said:
Hi would you please tell me about Sanyo inventer 180 model sap-250vs

Reply:

See MANUALS & PARTS GUIDES - HVAC where you can find contact information to obtain Sanyo manuals and technical guides

Question: Burnham B870WHEB split AC unit

Aug 30, 2015) M lambright said:
I have a Burnham B870WHEB split AC unit. I cannot find any info in this. I have a condensate leak - not sure if it has a pump or just a tray and how to trouble shoot

Reply:

f your spit system is a wall or ceiling mounted unit indoors typically the condensate drains by gravity.

If the condensate drain is clogged or the unit is askew on the wall those conditions can make the little condensate drip tray inside the split system wall unit overflow.

See MANUALS & PARTS GUIDES - HVAC where you can find contact information to obtain Burnham manuals and technical guides

Question: Cleaning or maintenance of a Mirage ductless air conditioner temperature probe

(Sept 12, 2015) Kyler said:
Is there any maintenance or cleaning that can be done on a Mirage ductless air conditioner temperature probe? It seems as if it is not as sensitive anymore. When the AC temperature is set on 78 degrees it now does not cool as much as it used to on the same 78 degree setting.

The AC cools fine when the temperature is lowered, but it seems like the temperature probe is not as sensitive or something like that. Thank you in advance.

Reply:

Yes:

Remove the unit covers, find the probe or temperature sensor. Normally it's mounted on the face of the cooling coil, in the air path.

Check that the probe is not loose, has not fallen away, and that it is not covered or the coil fins around it clogged by dust and debris. If the coil is dirty it should be cleaned by your service tech. Be careful about DIY vacuuming as you risk damaging the coil fins.

If the sensor probe is clean, visually intact and secure, but if it is not sensing temperature it may need replacement: a job for an HVAC service technician not a homeowner.

See MANUALS & PARTS GUIDES - HVAC where you can find contact information to obtain Mirage ductless AC manuals and technical guides

Looking in the manual for a Mirage 15 system I don't see any probe-specific maintenance for the Mirage split system ductless A/C sensor; I would look carefully for

- looseness: the probe should be snugly in place against the coils
- corrosion or dirt or debris - you might spray a small amount of AC Coil cleaner on the area
- dirty filters

The system could have a different problem: loss of refrigerant.

(Sept 12, 2015) Kyler said:
danjoefriedman, thank you for the quick reply. The AC seems to work fine, the temperature sensing just seems to be off a couple degrees. If I lower the temp a couple degrees cooler than normal it has no problem staying nice and cool. I did inspect it and I think I see a thermistor installed in what looks to be the correct position against the coils. It looks completely clean and the filters are cleaned regularly. Do you suggest I still check the refrigerant? Thanks again.

Reply:

No. Check the location of the remote control thermostat.

Question: mini split single zone heat pump makes clicking noises

2015/12/14 Andrew said:
I have a mini split single zone heat pump/ ad in its second season of use. From day one, it has made clicking and clacking noises throughout the heating process. Sounds like expansion but it is loud and prevents a good nights sleep. I thought these things were supposed to be quite! Help!

Reply:

Are you hearing the noise when the backup heat is on?

If so check for thermal expansion of metal components and piping or for slight movement of the unit on the wall.

...

Continue reading at SPLIT SYSTEM AIR CONDITIONERS & HEAT PUMPS - topic home, or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see SPLIT SYSTEM A/C & HEAT PUMP FAQs-2 - more-recent questions and answers about split system AC and heat pump units.

Or see these

Recommended Articles

• DIAGNOSTIC GUIDE A/C or HEAT PUMP
• DIAGNOSTIC DETAILS A/C or HEAT PUMP
• COMPRESSOR / CONDENSER REPAIR
• MANUALS & PARTS GUIDES - HVAC - home - Master Index to All Brand Names & HVAC manuals, wiring diagrams, installation and repair guides
• SPLIT SYSTEM AIR CONDITIONERS & HEAT PUMPS
  • CONTROLS for Split System (Ductless) Air Conditioner Thermostats & Operating Controls
  • AIR FILTER MAINTENANCE for Split System Air Conditioner - How to Clean a Split System Air Conditioner Filter
  • A/C CONDENSATE DISPOSAL for Ductless or Split System Air Conditioners
  • SUPPORT SAFETY WARNING for Wall-Mounted Exterior Air Conditioner / Heat Pump Compressor/Condenser Units or Window Air Conditioner Units
  • DIAGNOSE WEAK AIR FLOW from a split system air conditioner or heat pump
  • DIAGNOSE INADEQUATE HEATING or COOLING, SPLIT SYSTEM from a split system air conditioner or heat pump
  • REMOTE CONTROL THERMOSTAT FIX or REPLACE for an air conditioners or heat pump
• SPLIT SYSTEM AC / HEAT PUMP REPAIRS

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INDEX to RELATED ARTICLES: ARTICLE INDEX to AIR CONDITIONING & HEAT PUMPS

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