What Causes the Emergency Heat Setting to Stay On? A Dallas Homeowner's Guide
Your home is warm again after a cold stretch in Dallas — but your thermostat is still showing EM Heat. Temperatures outside have risen. Nothing changed on your end. Yet the system keeps running on backup heat and won't switch back.
EM Heat is built to run for short periods during a heating emergency. When it stays on longer than it should — especially during mild weather — something in the system is keeping it there. Three causes account for most of these situations: a thermostat malfunction, a heat pump fault, or a wiring error.
Each cause prevents the system from handing control back to the heat pump. Each one also requires a Dallas licensed AC repair technician to diagnose correctly. If your EM Heat is stuck on right now, our Dallas heating team is available to take a look.
The Three Main Reasons EM Heat Stays On
Your heat pump and backup heat strips are designed to hand off control automatically. When outdoor conditions improve, the heat pump should restart and the backup strips should stop. When that handoff does not happen, one of three things is preventing it.
Cause | What It Means | Next Step |
Thermostat malfunction | The thermostat fails to signal the heat pump to restart | Professional thermostat diagnostic |
Heat pump fault | The outdoor unit cannot take back over from the backup strips | Heat pump inspection and repair |
Wiring error | A circuit or connection issue keeps the system locked in emergency mode | Control wiring continuity check |
All three causes share one thing in common — none of them resolve on their own. There is no homeowner reset that reliably clears a stuck EM Heat setting when one of these faults is the root cause. The system will keep running on backup heat until the underlying problem is found and fixed.
Thermostat Malfunctions That Lock In Emergency Heat
Your thermostat is what tells the system when to switch between the heat pump and backup heat. When it malfunctions, that switching signal breaks down. The heat pump never gets the instruction to restart — so EM Heat keeps running.
Several types of thermostat faults can cause this. A failed temperature sensor may stop reading outdoor or indoor conditions accurately. A firmware glitch in a smart thermostat can freeze the system in its last active mode. Internal wiring faults inside the thermostat unit can cut off communication with the heat pump entirely.
Dallas homes with Nest, Ecobee, and Honeywell Home thermostats are not immune to this. Our technicians see mode-switching failures across all three brands — often after a software update or a power interruption during a cold snap.
Watch for these signs that the thermostat is your cause:
- EM Heat stays on after outdoor temps rise above 40°F
- Manual mode changes on the thermostat do not register or take effect
- The display behaves inconsistently — flickering, freezing, or showing incorrect readings
- The system behavior changed after a recent power outage or thermostat update
A technician will test the thermostat's signal output directly. If it is failing to send the heat pump restart command, the unit will need recalibration or replacement. In most cases, this is a straightforward repair that gets your system back on the heat pump the same day.
Heat Pump Faults That Prevent the System From Switching Back
When the heat pump cannot operate, the system has nothing to switch back to. EM Heat stays on because the backup strips are the only source of heat still functioning. The heat pump is not recovering — it is out of service.
Several heat pump faults produce this outcome. Refrigerant loss reduces the system's ability to move heat and can cause the unit to stop running entirely. A frozen outdoor coil locks the unit in place until a full defrost cycle completes — or until a technician intervenes. A failed reversing valve traps the system in one operating mode and prevents the heat pump from re-entering heating operation.
A frozen coil is the most frequent cause our Dallas technicians find after a cold snap. The unit ices over during extreme temperatures and cannot restart on its own once conditions improve. Left unaddressed, the ice buildup puts additional strain on the compressor.
Compressor failure is the most serious outcome. If the compressor has failed, the heat pump will not recover without major repair or full system replacement.
Watch for these signs that a heat pump fault is your cause:
- The outdoor unit is not running at all
- Visible ice on the outdoor unit that has not cleared after several hours
- Unusual sounds — grinding, clicking, or rattling — before the heat pump stopped
- The system was running normally before a period of extreme cold
Wiring Errors That Keep Emergency Heat Active
Your heat pump and backup strips communicate through a set of low-voltage control wires. These wires carry the signals that tell the system when to switch modes. When one of those connections fails, the system can get locked in emergency mode — even if the thermostat and heat pump are both working correctly.
Wiring faults are the least obvious of the three causes. They do not produce the same visible symptoms as a frozen outdoor coil or a flickering thermostat display. The system simply stays in EM Heat with no clear explanation — which is why this cause is the one most likely to be missed if a diagnosis stops too early.
Three wiring situations account for most of these cases in Dallas homes. A loose connection at the thermostat terminal block can interrupt the heat pump restart signal. A damaged or degraded wire — common in older Dallas properties where original wiring has never been replaced — can break the circuit intermittently. An incorrect terminal assignment after a DIY thermostat installation can wire the system in a way that permanently favors emergency mode.
Watch for these signs that a wiring fault is your cause:
- EM Heat activates randomly with no clear pattern or weather trigger
- System behavior changed after a recent thermostat installation
- No thermostat fault or heat pump fault has been found during previous inspections
- The home is older and the control wiring has not been updated
A technician will run a continuity check across all control wires and inspect every terminal at both the thermostat and the air handler. A wiring fault found at this stage is typically a straightforward fix — but it has to be found first.
What Happens If You Leave Emergency Heat Running Too Long
The impact starts with your electricity bill. Electric resistance strips deliver one unit of heat for every unit of electricity they consume. Your heat pump delivers two to three units of heat for the same amount of electricity. Every day your system runs in emergency mode, that gap shows up on your Oncor delivery charges and your retail electricity rate.
Running EM Heat for several days without resolving the underlying cause can add significantly to a winter utility bill in Dallas. Most homeowners do not realize how fast those charges accumulate until the bill arrives.
The cost impact is only part of the problem. Backup resistance strips are not built for continuous operation. Extended use puts strain on components that are designed to run occasionally — not as a primary heat source for days at a time. The longer they run without a break, the greater the risk of a secondary failure on top of the original fault.
The underlying cause does not improve on its own. A thermostat fault will not recalibrate itself. A frozen coil or failed reversing valve will not self-correct. A wiring error will not reconnect. Each day the system stays in emergency mode is another day the root problem goes unresolved — and in some cases, worsens.
Dallas homeowners who call sooner typically face a simpler repair than those who wait through a full billing cycle. Our Dallas HVAC team can run a same-day diagnostic to identify which of the three causes is keeping your EM Heat active and get your heat pump back online.
Your Dallas Heat Pump Deserves a Same-Day Answer
If your EM Heat is still running and your heat pump has not restarted, the cause is not going to clear on its own. A thermostat fault, a heat pump problem, or a wiring error — all three require a technician to diagnose and repair correctly. Every day the system stays in emergency mode costs more and puts additional strain on components not built for extended use.
Berkeys Plumbing, A/C & Electrical has been diagnosing and repairing heating systems for Dallas homeowners since 1975. Our licensed HVAC technicians carry diagnostic equipment to identify thermostat faults, heat pump failures, and wiring errors on the same visit. We explain what we find in plain language and give you your options before any work begins.
Same-day service is available throughout Dallas, Park Cities, East Dallas, Lakewood, and the White Rock Lake area.
Frequently Asked Questions
Three causes keep emergency heat running longer than it should: a thermostat malfunction, a heat pump fault, or a wiring error. Each one prevents the system from handing control back to the heat pump. All three require a licensed HVAC technician to diagnose and repair correctly.
Call a licensed HVAC technician as soon as possible. A failing emergency heat system during cold weather leaves your home without a backup heat source. Do not attempt to reset or repair the system yourself — incorrect handling can make the underlying fault harder to diagnose.
A properly functioning emergency heat system produces steady, consistent warmth throughout your home. If you notice a sudden drop in heat output, uneven heating across rooms, or a sharp rise in your electricity bill without a change in usage, those are signs the system may not be operating correctly.
The most frequent heating problems during a crisis are sudden heat loss from equipment failure, a heat pump that will not restart after extreme cold, and emergency heat that activates but fails to maintain temperature. Skipping routine maintenance increases the likelihood of all three — especially heading into a Dallas winter.
Yes. Emergency heat uses electric resistance strips that consume significantly more electricity than a functioning heat pump. Running it for more than a day or two will produce a noticeable increase on your Oncor electricity charges. The faster the underlying heat pump issue is resolved, the sooner your costs return to normal.