What causes Trane HVAC System 158?

Low airflow across the indoor coil, for example a clogged air filter, closed or blocked supply vents or return grilles, or a dirty coil. Low refrigerant charge, usually from a leak. The indoor coil temperature (ET) sensor is out of calibration and reading colder than the coil really is. Running in cooling during low outdoor temperatures, which Trane says can make this alert normal.

How do I fix Trane HVAC System 158?

Note whether the code shows as 158.00 and when it appeared, for example after a cool night or a long cooling run. Replace or clean the air filter, even if it was changed recently, and check that the filter is the right size and seated properly. Open every supply vent and make sure return grilles aren't blocked by furniture, rugs or curtains. If you can see ice on the indoor coil or the refrigerant lines, turn cooling off and run the fan only (or leave the system off) until it has fully thawed before running cooling again. Don't chip at ice on the coil. Make sure the condensate drain and pan can handle the melt water so nothing overflows while the coil thaws. After the coil has thawed and the filter is clean, run cooling normally. The system shuts the compressor off for 5 minutes on this alert, so give it time. If ERR 158 keeps coming back in normal weather, call a technician.

When should I call a pro for Trane HVAC System 158?

ERR 158 keeps returning with a clean filter, open vents and normal outdoor temperatures. There is ice on the coil or lines again shortly after thawing, or the system isn't cooling well. You suspect low refrigerant charge or a leak; checking and repairing charge needs a licensed technician. The coil itself looks dirty or the blower seems weak, or the ET sensor needs to be checked against Trane's specifications. ERR 158 appears together with superheat alerts such as 156, which point toward a charge or restriction problem.

Code: 158❄️ Trane HVAC System

Trane / American Standard Error 158: Indoor Coil Frost Protection (Meaning, Causes, Fixes)

Q: What does Trane HVAC System 158 mean?

ERR 158 on a Trane or American Standard communicating thermostat means Indoor Coil Frost Protection: the indoor coil temperature sensor has read freezing for 20 minutes in a row, so the system shut the compressor off for 5 minutes to let the coil thaw. Trane lists low airflow, low refrigerant charge and an out-of-calibration coil sensor as the causes, and says the alert can be normal after running in low outdoor temperatures. Start with a clean filter and open vents. Trane's System Alert Guide (August 2020) lists ERR.158.00 as Indoor Coil Frost Protection: the indoor evaporator temperature sensor (the ET sensor) has been below freezing for 20 consecutive minutes, and the compressor is shut down for 5 minutes. The possible causes it gives are low airflow, low refrigerant charge, and the indoor ET sensor being out of calibration. It also notes that low outdoor ambient conditions can trigger it, and that in that case the alert would be normal. Trane's ComfortLink II alert table lists the same alert as CL2.158.00, priority Major, short name ID COIL FRST, triggered when the ET sensor has seen 32 degrees or below for 20 consecutive minutes, with the same causes and the same note about low outdoor temperatures. In plain terms, the system is protecting itself from a coil that is icing up. A coil that freezes repeatedly usually points to air not moving across it fast enough (a clogged filter, closed or blocked vents, a blocked return or a dirty coil, which are general airflow checks rather than items Trane lists by name) or to a refrigerant problem a technician has to diagnose. The next code in the guide, 159, is an unrelated communication fault inside the indoor unit; if you see high superheat alerts as well, see our Trane 156 page, since Trane lists low charge for both.

Reviewed 2026-10-25 · Based on 2 manufacturer & service sources

What the code means

Trane's System Alert Guide (August 2020) lists ERR.158.00 as Indoor Coil Frost Protection: the indoor evaporator temperature sensor (the ET sensor) has been below freezing for 20 consecutive minutes, and the compressor is shut down for 5 minutes. The possible causes it gives are low airflow, low refrigerant charge, and the indoor ET sensor being out of calibration. It also notes that low outdoor ambient conditions can trigger it, and that in that case the alert would be normal. Trane's ComfortLink II alert table lists the same alert as CL2.158.00, priority Major, short name ID COIL FRST, triggered when the ET sensor has seen 32 degrees or below for 20 consecutive minutes, with the same causes and the same note about low outdoor temperatures. In plain terms, the system is protecting itself from a coil that is icing up. A coil that freezes repeatedly usually points to air not moving across it fast enough (a clogged filter, closed or blocked vents, a blocked return or a dirty coil, which are general airflow checks rather than items Trane lists by name) or to a refrigerant problem a technician has to diagnose. The next code in the guide, 159, is an unrelated communication fault inside the indoor unit; if you see high superheat alerts as well, see our Trane 156 page, since Trane lists low charge for both.

Likely causes

Low airflow across the indoor coil, for example a clogged air filter, closed or blocked supply vents or return grilles, or a dirty coil
Low refrigerant charge, usually from a leak
The indoor coil temperature (ET) sensor is out of calibration and reading colder than the coil really is
Running in cooling during low outdoor temperatures, which Trane says can make this alert normal

Safe DIY checks

⚠ Before you start

Turn off power at the furnace/HVAC service switch and the breaker before opening panels.

Note whether the code shows as 158.00 and when it appeared, for example after a cool night or a long cooling run.
Replace or clean the air filter, even if it was changed recently, and check that the filter is the right size and seated properly.
Open every supply vent and make sure return grilles aren't blocked by furniture, rugs or curtains.
If you can see ice on the indoor coil or the refrigerant lines, turn cooling off and run the fan only (or leave the system off) until it has fully thawed before running cooling again. Don't chip at ice on the coil.
Make sure the condensate drain and pan can handle the melt water so nothing overflows while the coil thaws.
After the coil has thawed and the filter is clean, run cooling normally. The system shuts the compressor off for 5 minutes on this alert, so give it time. If ERR 158 keeps coming back in normal weather, call a technician.

🛠 When to call a pro

ERR 158 keeps returning with a clean filter, open vents and normal outdoor temperatures.
There is ice on the coil or lines again shortly after thawing, or the system isn't cooling well.
You suspect low refrigerant charge or a leak; checking and repairing charge needs a licensed technician.
The coil itself looks dirty or the blower seems weak, or the ET sensor needs to be checked against Trane's specifications.
ERR 158 appears together with superheat alerts such as 156, which point toward a charge or restriction problem.

Parts that commonly fix it

Always match the part number to your exact model.

⚙

HVAC air filter

Low airflow is the first cause Trane lists. Match the size printed on your current filter.

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⚙

Refrigerant leak detector

Low charge is the second cause Trane lists. A technician will confirm and repair any leak.

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⚙

Digital multimeter

For a technician-style check of the indoor coil (ET) sensor against Trane's resistance chart.

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Sources

Last reviewed 2026-10-25. Always confirm against the manual for your exact model number.

Trane / American Standard Error 158: Indoor Coil Frost Protection (Meaning, Causes, Fixes)

What the code means

Likely causes

Safe DIY checks

🛠 When to call a pro

Parts that commonly fix it

HVAC air filter

Refrigerant leak detector

Digital multimeter

Related codes

Sources