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Heat Guardian 1.0
Online Help

The Heat Guardian system consists of two identical hand-held units. The simplest way to think about this is that it’s like a walkie-talkie but it only sends temperature, signal, and battery. Each unit shows the other unit’s values. Looking at the unit in your hand, you see the temperature, battery and signal level of the unit in your vehicle. 

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The Display

When you look at the unit in your hand, it’s showing the temperature, battery, and signal strength at the other unit.

Temperature: the temperature is displayed to the nearest degree.  It is guaranteed accurate to ±2°Fahrenheit with typical accuracy of ±0.2°F. The two units communicate every thirty seconds or so. The temperature sensor is in the Heat Guardian so it may take a few minutes to stabilize to ambient temperature.

Battery: in normal use (with good signals) it should last an entire weekend (3 days of 10 hours a day). Each unit may be charged by a standard USB power supply or computer.

Signal: this is just like a cell phone. When the signal gets below 1 bar it may still be sending and receiving data but it may not.

Typical Range

If one unit is on a flagpole in an open field the range will be about 5 miles. In real life they may go less than ½ a mile in dense woods or in metal buildings. Mount the unit in your vehicle in a window so that the signal goes through a window instead of a car or rv wall. 

When the display shows 4 or 5 bars you have plenty of signal and should not worry at all about positioning or location. When the display shows 0 or 1 bars it may help to align the antennas as discussed below in mounting.

When out of range or if there is interference, the Heat Guardian will (a) within 40 seconds start counting the time since it last received a packet (b) after a minute it will loudly warble every 15 seconds (c) after two minutes it will blank out the remote temperature.

In all cases, the blinking light confirms connection status. Every few seconds it blinks green, orange or red.

We offer bigger long range antennas as an option. They can be unwieldy but they double the range.

How to Turn It Off and On

The unit has one button.

Press and hold the button for about 7 seconds until the display blanks and the unit will turn off.

If the unit is off, press and hold the button for about 7 seconds until the display comes on to turn it on.

Click the button once to briefly show the settings for the unit you are holding, instead of the remote settings. The status will show “Local” (for Local settings) when that happens.


The plastic shell and circuit boards for the unit should be good up to about 180°F. The replaceable battery may fail at as low as 150°F. Do not charge the unit at temperatures above 110°F.


To charge the Heat Guardian, plug a power supply micro-usb cable into the side. When it is charging an orange LED light will appear near the plug. When it is fully charged the light turns off. (On H6 units the display will always show full battery when the units are plugged in.)


Charging time depends on your charger but will range from 20 minutes to over an hour.

Out of Distance Range


When the Heat Guardian units are out of range of each other:

  • After 40 seconds the status bar will show how long since the last connection

  • After 60 seconds the Heat Guardian will warble every ten seconds (or so) for 30 seconds and the blinking light will turn orange (on H7 units this looks quite red).

  • After 2 minutes the Heat Guardian temperature display will flash on/off every ten seconds and the blinking light will turn red.

Out of Temperature Range

When the remote Heat Guardian unit is too hot or too cold (based on your temperature range settings) the blinking light on the local unit will become almost solid red (blinking just enough to let you know the unit is working correctly).

The Heat Guardian will also warble an out-of-temperature-range warning until you click the button.

The almost-solid red light will continue until the temperature comes within range.

Blinking Lights

When the unit is working normally you will see a green blinking light through the front near the cute dog.

In case of disconnect, after one minute the light will be orange. After two minutes the green light will change to red. If you see the Green LED blinking the units are communicating.

Any blinking light shows the unit is running. If that light stops blinking then the Heat Guardian has crashed or (more likely) the battery is run down. In the unlikely event the software has crashed, the Heat Guardian will automatically reset after 2 minutes.


Typical Usage


The Heat Guardian can be hung by the loop. The antenna is in the loop so try to ensure the antenna is upright and has a view through a window.

If you lay the Guardian on its side (so the antenna is horizontal) the range will decrease. If you put the Guardian in a metal box the range will decrease.

For maximum range: if you place it on a crate or a table, place it upright. The antenna is in the loop on top. You can double the range simply by rotating each unit so the loop points at (is parallel to) the other unit.


Please don't place your fingers on the display. Don't use at temperatures above 140F. The Heat Guardians are pretty robust but don't throw them at walls.

Antenna Upgrade

We offer a more expensive unit with a long (nearly 6") antenna instead of the loop. This doubles the range.


The radio band used by Heat Guardian is also used by some garage door openers. So, you may get interference and the every-30-seconds packet can sometimes be lost. This is not a disaster.

When one unit does not receive a packet it immediately increases the transmitter power and starts sending more frequently - trying to find the other unit at the cost of battery life. Usually they will resynchronize within a minute if it was a household appliance interfering.

Multiple Heat Guardians may also interfere with each other. Heat Guardians work on a specific channel (of which there are about 500 available) so it's unlikely they will interfere but not impossible. In addition to channels, each Heat Guardian has a unique ID so they will only communicate with their paired unit. Contact us if you want to change the channel.

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