H71 and H72 usually mean that a European Nest thermostat has lost communication with its Heat Link—the receiver installed near the boiler or heating equipment. That can be caused by a temporary wireless or power problem, pairing failure, interference, or a defective Heat Link. It does not automatically mean that the boiler has failed, and there is no verified evidence of a Google-wide outage.
If you need heat immediately, press the Heat Link button once on a 2nd- or 3rd-generation Nest Learning Thermostat, or twice on Nest Thermostat E. Manual heating stays on until you turn it off again, so do not leave it running unattended. See Google’s manual-heating instructions.
What H71 and H72 mean
The Heat Link is the hard-wired receiver that communicates wirelessly with the Nest thermostat and switches or modulates the heating system. It is used with European installations of the 2nd- and 3rd-generation Nest Learning Thermostat and Nest Thermostat E. Google explains the European Heat Link system here.
- H71: the thermostat cannot connect to the Heat Link.
- H72: a related Heat Link or power/connection problem. It is not proof that the boiler itself has failed.
These codes are different from a simple Nest app or Wi-Fi problem. The app may be unavailable while local thermostat-to-Heat Link control still works, or the app may work while the Heat Link has lost power or wireless contact.
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- ENERGY STAR certified smart thermostat for home that helps you save energy and stay comfortable.Connectivity : Wi-Fi - 802.11b/g/n 2.4 GHz, 802.11a/n 5 GHz Wi-Fi., Wireless interconnect : Bluetooth Low Energy Please refer to the product description section below for all applicable legal disclaimers.Product note: You can also check your system’s compatibility before purchasing a Nest thermostat with our online Nest Compatibility Checker on the Google Nest support page
- The Nest Thermostat is designed to work without a C wire in most homes, but for some systems, including heating only, cooling only, zone controlled, and heat pump systems, you’ll need a C wire or other compatible power accessory
- Nest Thermostat turns itself down when you leave, so you don’t waste energy heating or cooling an empty home. Lock feature: No
- Programmable thermostat that lets you create an energy efficient schedule in the Google Home app on your Android or iPhone
- Remote control lets family members change the thermostat temperature from anywhere on a phone, laptop, or tablet[1]
Is Google Nest experiencing an outage?
Check the Nest status page before resetting anything. The available status information showed Nest thermostat services, apps, setup and pairing as operational. That makes a local power, pairing, interference or hardware fault more likely, although a normal status page cannot rule out a regional or intermittent problem.
Reports from multiple owners can indicate a pattern, but they do not establish a confirmed Google-wide incident, recall or defective batch. If Google publishes a dated incident, follow its recovery guidance rather than repeatedly factory-resetting the system.
Check these details before resetting
Record the exact error and the Heat Link’s status light:
- Green: generally indicates normal operation on the relevant European models.
- Yellow: indicates that the Heat Link is disconnected.
- Blue or blinking: may indicate pairing, setup or reset activity, depending on the model.
- No light: suggests a power, wiring or hardware problem rather than a wireless fault alone.
Also note whether the thermostat display is powered, whether pressing the Heat Link button turns on the heating, and whether the fault affects heating, hot water or both. Google’s light guidance is available in its troubleshooting documentation.
Fix H71 or H72 in the safest order
1. Restart the Heat Link
A restart preserves settings and should be tried before a factory reset.
Rank #2
- Nest’s smartest, most advanced thermostat yet, the Google Nest Learning Thermostat (4th gen) is a beautiful, brilliant way to save energy, keep your home comfortable, and help make sure your heating and cooling systems are running smoothly[4]
- Savings you can count on: The Nest Learning Thermostat can help save up to 31% on heating and cooling bills [2]
- Improved compatibility: It works with most 24V systems, including gas, electric, oil, forced air, heat pump, and radiant, and no C wire is required for installation in most homes; visit the Nest Compatibility Checker for more info[5]
- Easy control in the Google Home app: Adjust on your phone from anywhere[1] or by using your voice with Alexa, Siri, or Google Assistant smart speaker[3], it’s easy to install yourself and it’s Matter compatible for simple integration into your smart home[5]
- Beautiful design: With a 60% larger display[11] and Dynamic Farsight, you can see info from across the room[1]; choose the design, like a clock or the weather; it automatically adjusts brightness for the best readability or you can adjust manually
- 2nd- or 3rd-generation Nest Learning Thermostat: press and hold the Heat Link button for about 10 seconds, then release it.
- Nest Thermostat E: press and hold the button for about 8 seconds, releasing it when the light pulses blue.
Wait for the unit to restart. Green indicates reconnection; yellow means it remains disconnected. Do not hold the button for around 20 seconds unless you intend to factory-reset the Heat Link. See Google’s restart and reset instructions.
2. Move the thermostat closer
Temporarily move the thermostat close to the Heat Link. Remove obstructions such as large metal objects, mirrors, refrigerators and other dense materials between the two devices. Other equipment using the 2.4 GHz band can also interfere with the connection. If the thermostat reconnects nearby but fails in its normal position, range or interference remains a likely cause.
3. Restart the thermostat
Do this only after confirming that the Heat Link itself has power. Use Google’s thermostat restart instructions for your model rather than repeatedly removing power from the heating installation.
4. Factory-reset only if necessary
A factory reset can restore pairing, but it can also remove settings or account associations. It is not the correct first response to H71 or H72.
3rd-generation Heat Link
- Hold the button for about 20 seconds.
- The light turns off and then rapidly blinks yellow.
- Release the button and wait for the reset to finish; the light should pulse blue.
- The Heat Link should normally reconnect automatically. If prompted, enter the six-character code on its bottom.
2nd-generation Heat Link
- Hold the button for about 20 seconds.
- The light turns off and then rapidly blinks green and yellow.
- Release the button and wait for the reset to finish.
- Enter the six-character pairing code if the thermostat requests it.
Heat Link E
- Remove the Heat Link from the account in the app.
- Hold its button for about 20 seconds and wait for the pulsing blue light.
- In the app, select Settings → Add product.
- Scan the QR code inside the Heat Link cover and follow setup.
Resetting the software does not require opening the mains wiring compartment. Never alter boiler wiring or work inside a live electrical enclosure unless you are properly qualified and the power has been isolated correctly.
Rank #3
- ENERGY STAR certified smart thermostat for home that helps you save energy and stay comfortable.Control the temperature with your voice using smart home devices that work with Google Assistant or Alexa[3]Nest Renew makes it simple to support clean energy right from home; it works with your Nest Thermostat[5] to help you automatically prioritize your usage[6] to times when energy is cleaner or less expensive.Product note: You can also check your system’s compatibility before purchasing a Nest thermostat with our online Nest Compatibility Checker on the Google Nest support page
- The Nest Thermostat is designed to work without a C wire in most homes, but for some systems, including heating only, cooling only, zone controlled, and heat pump systems, you’ll need a C wire or other compatible power accessory. You can control your Nest Thermostat manually when there's no internet connection.
- Nest Thermostat turns itself down when you leave, so you don’t waste energy heating or cooling an empty home
- Programmable thermostat that lets you create an energy efficient schedule in the Google Home app on your Android or iPhone
- Remote control lets family members change the thermostat temperature from anywhere on a phone, laptop, or tablet[1]. | Control the temperature with your voice using smart home devices that work with Google Assistant or Alexa[3].
Turn the heating on manually
If the house is cold while you troubleshoot:
- Nest Learning Thermostat, 2nd or 3rd generation: press the Heat Link button once.
- Nest Thermostat E: press the Heat Link button twice.
Press again—or press twice again on Thermostat E—to turn manual heating off. Manual heating bypasses the schedule and may not provide OpenTherm modulation. If your system controls domestic hot water, hot water may also turn on. Most importantly, manual heating continues until you switch it off, even if the thermostat later reconnects.
What the symptoms suggest
| What you see | Most likely interpretation | Next step |
|---|---|---|
| Yellow Heat Link light | Thermostat-to-Heat Link connection is lost | Restart, reduce interference and move the thermostat closer |
| No Heat Link light | Possible loss of mains power, wiring fault or failed electronics | Do not open the unit; arrange professional inspection |
| Manual heating works | The switching path may still be functional, but wireless control is not healthy | Turn manual mode off later and continue pairing/support checks |
| Manual heating does not work | Possible Heat Link, boiler, relay, power or wiring fault | Check the boiler’s own controls and contact a qualified professional |
| H71/H72 returns after reset | Persistent pairing, interference, power or hardware problem | Contact Google and consider a compatible replacement |
When the Heat Link may be defective
A hardware failure becomes more likely when the Heat Link has no status light despite an apparently powered heating system, repeatedly returns to H71 or H72 after the official restart and pairing steps, will not enter the expected reset or pairing state, or switches the heating inconsistently. These signs are not conclusive: a tripped fuse, boiler control fault, wiring issue or radio interference can produce similar symptoms.
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Replacement and re-pairing
If Google or a professional confirms that the Heat Link must be replaced, do not assume that any used Heat Link is compatible. Generation, region, wiring arrangement and pairing process matter. A replacement Heat Link should be matched to the existing thermostat and heating system.
For a replacement Heat Link with a Nest Learning Thermostat:
Rank #4
- Nest’s smartest, most advanced thermostat yet, the Google Nest Learning Thermostat (4th gen) is a beautiful, brilliant way to save energy, keep your home comfortable, and help make sure your heating and cooling systems are running smoothly[4]
- Savings you can count on: The Nest Learning Thermostat can help save up to 31% on heating and cooling bills[2]
- Improved compatibility: It works with most 24V systems, including gas, electric, oil, forced air, heat pump, and radiant, and no C wire is required for installation in most homes; visit the Nest Compatibility Checker for more info[5]
- Easy control in the Google Home app: Adjust on your phone from anywhere[1] or by using your voice with Alexa, Siri, or Google Assistant smart speaker[3], it’s easy to install yourself and it’s Matter compatible for simple integration into your smart home[5]
- Beautiful design: With a 60% larger display[11] and Dynamic Farsight, you can see info from across the room[1]; choose the design, like a clock or the weather; it automatically adjusts brightness for the best readability or you can adjust manually
- Select Replace Heat Link on the H71 screen.
- Wait for the Heat Link light to blink blue.
- Select Continue.
- Enter the six-character pairing code printed on the bottom of the Heat Link.
- Allow pairing to complete.
Because the Heat Link is connected to heating-system wiring, Google recommends professional installation. See the official replacement and pairing guide.
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Will Google replace the Heat Link?
Use Google’s warranty checker and claims process. Have the model, serial number, purchase date, proof of purchase, error code and photographs of the status light ready.
Depending on the country, region, warranty status and case details, Google may offer repair, replacement or a refund at its discretion. Accidental damage is excluded under the stated terms. Do not assume that an out-of-warranty unit will be replaced free of charge; anecdotal reports of free replacements are not a universal policy.
When to call a heating professional
- The Heat Link has no light or appears to have no power.
- The boiler does not respond to manual heating.
- A fuse, breaker, wiring or boiler control circuit may be involved.
- The boiler shows its own fault code.
- The Heat Link needs to be removed or replaced.
- Your home has no heat, particularly during freezing weather or where vulnerable occupants are present.
Use a qualified heating engineer or electrician. Google Nest Pros are independent installers or contractors, not Google employees. Do not open a mains-connected Heat Link or change boiler wiring as a DIY troubleshooting step.
Does this advice apply to every Nest thermostat?
No. H71/H72 and Heat Link procedures mainly concern European Nest Learning Thermostat and Nest Thermostat E installations. US-market Nest thermostats generally use a different setup and should not be treated as interchangeable. Confirm the thermostat model and country before following these button sequences.
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- Nest thermostats are designed to work without a C wire in most homes but for some systems, including heating-only, cooling-only, zone-controlled, and heat pump systems, you'll need a Nest Power Connector or C wire.
- The Nest Power Connector is a simple affordable alternative to a C wire if your heating and cooling system requires one to power your Nest Thermostat
- Installation is simple; the Nest Power Connector attaches to your furnace air handler, or zone controller and comes with simple instructions.
- The Nest Power Connector is only compatible with 24 VAC systems; it won't work with millivolt or high voltage systems
- The Nest Power Connector is the Nest thermostat C wire adaptor that's designed specifically for Nest thermostats
Quick checklist
- Confirm whether the code is H71, H72 or another code.
- Record the Heat Link light: green, yellow, blue, blinking or absent.
- Check Nest service status.
- Restart the Heat Link using the model-specific 8- or 10-second procedure.
- Move the thermostat closer and remove likely obstructions or interference.
- Use manual heating temporarily if required, and remember to turn it off.
- Factory-reset and re-pair only when the earlier steps have failed.
- Contact Google for warranty support or a qualified professional for power, boiler or wiring faults.
Frequently Asked Questions
Is H71 caused by Wi-Fi?
Usually H71 points more directly to lost communication between the thermostat and Heat Link. Wi-Fi or app problems can occur separately, but check the Heat Link light and local pairing first.
Does H72 mean the Heat Link is dead?
No. H72 can involve Heat Link power, pairing, wireless interference, thermostat power or hardware. A dead Heat Link is only one possibility.
Can I use my boiler without Nest?
You can often turn heating on temporarily through the Heat Link: once for a 2nd- or 3rd-generation Learning Thermostat, or twice for Thermostat E. Manual heating must be turned off again.
Is this a problem affecting all Nest users?
There is no verified evidence in the supplied sources of a confirmed Google-wide outage or universal defect. Individual or regional failures can still occur.
Can I replace the Heat Link myself?
The wireless pairing steps are straightforward, but the Heat Link is connected to heating-system wiring. Have replacement or removal carried out by a qualified professional.
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