What Do ClimateMaster Tranquility 30 Fault Codes Mean?

By Dave Hartzell, Master HVAC, IGSHPA Accredited, ClimateMaster GeoElite dealer, 47 years in the trade. Hartzell’s Heat & Air, Kingfisher, Oklahoma. Updated October 3, 2026.

ClimateMaster fault codes list (CXM2, DXM2, DXM2.5)

I built this table from ClimateMaster’s own control manuals, not from forum posts. The last column is what a homeowner can do without opening a panel. Everything past that column is my job.

How do I read the fault code on my ClimateMaster?

The red Fault LED on the control board tells you two things. A slow flash means the board is retrying after a fault. A fast flash means it has locked out. The code number itself shows on that LED in Test mode, and a communicating thermostat can show the last few lockouts without anyone touching the board. On the Tranquility 30, the board depends on the unit’s age: ClimateMaster’s current Tranquility 30 TE manual lists the DXM2.5, and older Tranquility digital units used the DXM2. Codes 1 through 9 read the same on both, so the table above holds either way. I confirm the model label before I trust a code on someone’s unit, because codes 10 through 15 change from board to board.

Should I reset a ClimateMaster lockout?

Leave that to the board and to me. A ClimateMaster board already retries most faults on its own, three times, before it locks out, and the two freeze-protection faults, codes 4 and 5, lock out on the first one. So by the time you see a lockout, the board has already told you the problem is real. ClimateMaster’s manuals say a lockout clears when the call for the compressor goes away at the thermostat, and in the same manuals they say not to restart a unit until somebody inspects it and fixes what tripped it, because equipment damage may occur. Write the code down, leave the system off, and call 405-375-4822. Flipping the breaker over and over does not fix anything, and it can run the compressor or pump outside its protection.

What do ClimateMaster codes 2 and 3 mean?

Code 2 is the high pressure switch and code 3 is low pressure, which the DXM boards call loss of charge. In heating, a code 2 on a geothermal unit usually traces back to airflow: a dirty filter, closed registers or a blower that quit. ClimateMaster’s service tool cause list for high discharge pressure puts a dirty filter and low airflow first in heating, and low water flow first in cooling. This summer I had a ClimateMaster geothermal unit locked out on high pressure, and the failure was the blower motor, not anything on the refrigerant side. A new motor fixed it. Code 3 can mean a refrigerant leak, and that is licensed work. Never add refrigerant yourself.

Does a ClimateMaster code 4 mean my loop is bad?

Almost never. Code 4 is LT1, freeze protection on the water coil. The sensor reads refrigerant temperature next to the water coil, and the board has a jumper, JW3, that sets the cutout at 30°F for plain water or 10°F for a loop with antifreeze. A code 4 can come from low flow, a worn loop pump, antifreeze that does not match that setting, or a bad sensor. It rarely means a dead loop. In 700+ geothermal jobs Hartzell’s Heat & Air has on record since 2017, I have not replaced one loop field. I have loops in the ground on their third generation of equipment.

“We don’t replace the loops. They last.”Dave Hartzell, Hartzell’s Heat & Air, Kingfisher

What wears is the pump that moves the water. Loop pumps and flow centers show up 45+ times in my geothermal records. Pressurizing and flushing a loop that has picked up air shows up 150+ times. Both are service work, not a new loop.

What does a ClimateMaster code 5 mean, and what can I safely do?

Code 5 is LT2, freeze protection on the indoor air coil of a ClimateMaster, and it mostly happens in cooling, which in Oklahoma means summer. ClimateMaster’s technical bulletin TBJ005 says code 5 is most commonly caused by low airflow across the coil or cold air coming back to the unit. Here is what you can safely do: turn cooling off and run the fan only to thaw the coil, then check the air filter. If it freezes again, call 405-375-4822. Do not chip ice or open the unit. Sometimes the sensor itself is the problem. The same bulletin says a failed sensor reads colder than the coil really is and causes nuisance code 5 lockouts, and I have replaced LT2 and FP2 freeze sensors on ClimateMaster units.

What does a ClimateMaster code 6 mean?

Code 6 is condensate overflow. Water reached the drain pan sensor and stayed there for 30 seconds, so the unit shut itself off before the pan could spill. In the 700+ geothermal jobs Hartzell’s Heat & Air has on record since 2017, drains and condensate came up 150+ times, the most common repair I find. Compressors, the part everyone worries about, came up fewer than 15 times. You can look for water around the unit from a safe distance and keep clear of the wiring. Clearing the line and fixing a bad trap is my job. Clearing a drain does not guarantee it stays clear, and an old line sometimes needs replacing.

Which ClimateMaster codes are not lockouts?

Code 7 is over or under voltage. ClimateMaster says plainly that it is not a fault or a lockout. The board waits for voltage to come back in range and starts on its own, so it often follows a storm or a power blip. Code 8 is the Unit Performance Sentinel, a warning that the unit is running hot or cold for its mode. The compressor keeps running through it. Neither one is an emergency, but a code 8 that keeps coming back is worth a diagnostic before it turns into a lockout.

What does a geothermal diagnostic cost in Oklahoma?

At Hartzell’s Heat & Air, the geothermal diagnostic is $348 flat. Weekday, night or weekend, it is the same $348, and it is the same for my maintenance plan members. I check loop pressure, refrigerant charge, the desuperheater, controls and the heat exchanger, and you get a written report and a quote before I leave. I work geothermal across Oklahoma out of Kingfisher, and I have taken care of 250+ geothermal customers and 300+ geothermal systems. I am IGSHPA Accredited and a ClimateMaster GeoElite dealer, with 4.8 stars and 300+ Google reviews. Everyday AC and furnace calls stay in my seven counties. Geothermal goes farther.

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