Masimo Rad-57 Pulse Oximeter Not Working in Cold Weather – Fix


Well, folks, it’s that time of year again. Temperatures are dropping and it seems like my trusty Masimo Rad-57 pulse oximeter doesn’t want to work when I head outdoors!


If you’re like me and use one of these handy little devices to monitor your blood oxygen saturation (SpO2), you’ve probably noticed it struggles in colder weather. It’s frustrating when you rely on the readings to manage a health condition, only to have your device freak out when temperatures take a dip.

After troubleshooting my finicky Rad-57 for a few winter seasons now, I’ve learned some tips and tricks to try and get it working properly again in the cold.

Masimo Rad-57 Pulse Oximeter Not Working in Cold Weather

Masimo Rad-57 Pulse Oximeter Not Working in Cold Weather


I’ll share what I’ve discovered so hopefully you can avoid choking the thing in frustration!


We’ll cover:

  • What makes the Rad-57 sputter in cold weather?
  • Step-by-step troubleshooting tactics.
  • When it’s time to call in a professional.
  • Some common questions about these cold weather issues.
  • A few extra resources in case you need more info.

Armed with the right knowledge, we can outsmart our touchy pulse ox and get it to cooperate even when Old Man Winter comes knocking!

What is Masimo Rad-57?

Let’s start with an introduction in case you aren’t familiar with this device. The Rad-57 is a popular portable pulse oximeter used in hospitals, doctor’s offices, EMS vehicles, sleep labs, and home use.

Here’s a quick rundown of its stats:

  • About the size of a small walkie-talkie.
  • Runs on 2 AAA batteries.
  • Clips onto your fingertip to read SpO2 levels.
  • It gives pulse rate and perfusion index readings too.
  • The handy display screen shows the readings.
  • Useful for checking oxygen levels, breathing issues, heart rate, etc.

It’s a pretty slick little unit for monitoring key vital signs on the go. I use mine to keep an eye on oxygen saturation since I have a respiratory condition. Lots of folks use them for sleep apnea, COPD, checking patient vitals, or athletic performance.


The problem is, this gadget doesn’t like cold weather! When temperatures dMakesit starts acting up with on tolerance.

Why Masimo Rad-57 Pulse Oximeter Not Working in Cold Weather?

Before we move on to solutions, it helps to understand exactly why our dear Rad-57 has a meltdown in chilly conditions. Here are a few ways good ol’ Mother Nature wreaks havoc:

  • Batteries drain faster: Cold saps battery life. My device eats through batteries twice as fast in winter shutdown batteries leading to erratic performance or sudden shutdown. Not cool (pun intended).
  • Sensors get affected: The optical sensor that reads SpO2 relies on blood flow. When blood vessels constrict from cold, the sensor doesn’t work as well. My readings tend to drop on really cold days.
  • Displays malfunction: Ever see your car dashboard digits go wonky in extreme cold? The same thing happens to the Rad-57’s display when temps plummet. Sections blank out or numbers jumble up. Brrrr!
  • Physical buttons and switches fail: Do you have trouble texting with gloved hands in winter? The mechanical buttons and switches inside the device can become sluggish and unresponsive in the cold too.
  • Condensation and moisture: Exposure to snow, rain, or condensation while outdoors can seep into the device around buttons, battery hatch, etc. leading to erratic function.

So in a nutshell, the cold impacts pretty much everything that makes the Rad-57 work! But take heart, with some tinkering we can get it back on track.

Step-By-Step Troubleshooting Guide to Fix Masimo Rad-57 Pulse Oximeter Not Working

When my recalcitrant pulse ox refuses to work in chilly weather, I break out my troubleshooting bag of tricks. Here are the steps I follow to try and resuscitate it:

  • Swap in Fresh Batteries

First things first – toss those tired batteries! Cold quickly kills off any lingering juice. I always keep spare AAA lithium or alkaline batteries on hand for winter Oximeter Rescue. The lithium batteries hold up best in freezing temps. Some people swear by keeping batteries warm in an inside pocket too. Give the new batteries a minute to acclimate before turning them on.

  • Warm It Up

If new batteries don’t coax a peep from your lifeless Rad-57, it needs a warming break. Bring it inside and let it rest for 20-30 minutes until it returns to room temperature. I’ll put mine on a heating pad or register vent to speed things up. This thawing-out period lets the internal components normalize.

  • Toasty Fingers Please!

Even all warmed up, my oximeter still throws a fit if my fingers are ice cubes. It needs good blood flow to work properly. So I make sure to pop hand warmers in my gloves and get my fingers toasty before attempting a reading outside. If you’re dedicated, some people run their hands under warm water first.

  • Try Different Digits

If one finger isn’t cutting it, try sampling other fingers. My middle or ring finger generally works better than index or pinky if my hands are super cold. Find the digit with the best capillary circulation.

  • Reset It

When all else fails, resetting the device often does the trick. Turn it off, remove the batteries for 30 seconds, then reinsert and power it on. This reboot re-calibrates its circuits to function in the prevailing conditions. Say a little prayer while it cycles back up!

  • Check for Wetness

Before resetting, carefully inspect your Rad-57 for any moisture or liquid that could have seeped into cracks around the buttons, battery hatch, or openings. Gently blot dry any wet spots you find. Even a little moisture in the wrong spot can make readings go haywire.

  • Contact Masimo

On the rare occasion, my ox is well and truly dead, it’s time to call in the experts at Masimo. Their technical support can often troubleshoot more advanced issues over the phone and recommend next steps, like returning for service if needed. Don’t attempt home repairs on the intricate internal components.

When to Seek Professional Help?

While basic troubleshooting resurrects my Rad-57 99% of the time, there are a few instances where professional service may be required:

  • It won’t power on at all after new batteries and resets.
  • Still won’t work above freezing with warm hands.
  • Visibly damaged or cracked display.
  • Reading accuracy doesn’t improve after finger-swapping.
  • The suspect moisture has damaged internal parts.
  • Buttons and ports no longer engage or respond.

If you’ve run through all troubleshooting steps with no dice, contact an authorized Masimo repair center or Masimo customer support. They can evaluate if a service, calibration, or part replacement is needed and give you a quote. Independent repair shops generally won’t tackle servicing the Rad-57.

In some cases of extreme damage, the device may need to be replaced. But Masimo technicians can make that determination once they diagnose the issues.

Pro tip: If your device is out of warranty but otherwise functional, repairs directly through Masimo are often surprisingly affordable. I had an out-of-warranty Rad-57 serviced for under $100 recently. Worth checking out before ditching your ox for a new one!



Here are answers to some commonly asked questions about using the Rad-57 pulse oximeter in frigid conditions:

  • Q: Do the cold weather issues permanently damage the Rad-57?

A: In most cases, no. The problems are temporary and it starts working normally again after warming up, swapping batteries, etc. However extreme or prolonged cold can potentially cause permanent electronic failure in some cases.

  • Q: Should I keep it in an inside pocket close to my body when going outside?

A: Yes! Keeping it tucked close to your body heat when venturing out in the cold helps keep the device warm enough to function. Just remember to warm those fingers up too before taking a reading.

  • Q: Does cold temperature affect all pulse oximeter models or just the Rad-57?

A: Cold can impact many makes and models of pulse oximeters. But from what I’ve researched, the Rad-57 seems more resistant than some competitors when it comes to low perfusion and temperatures.

  • Q: What batteries work best in cold weather?

A: Hands down, lithium batteries outperform alkaline and rechargeable batteries in freezing weather. Alkaline batteries drain faster but still work better than rechargeables in the cold. I avoid rechargeables below freezing if possible.

  • Q: Can I put the Rad-57 in a plastic bag outside to protect it?

A: A small Ziploc-type bag can help shield it from rain or snow when you’re out and about. But the device will still get cold in the bag, so warm it up as soon as possible afterward. Don’t seal it up completely airtight – it needs a little ventilation.

  • Q: How can I prevent issues next winter?

A: Keep spare lithium or alkaline batteries stocked. Store your Rad-57 above freezing when not in use. Bring hand warmers for outdoor use. Keep the battery terminals and openings clean and dry. Handle the device carefully to prevent damage.

  • Q: How cold is too cold for the Rad-57?

A: It’s rated to operate down to 41°F. But I’ve had issues as “warm” as 30°F if my fingers are icy. Keeping the device and hands warm helps extend its range.

  • Q: Can I use rechargeable batteries if I warm them up first?

A: It’s not recommended since they drain faster in cold conditions. But in a pinch, try keeping them warm against your body and swap them out frequently.

  • Q: Why does my SpO2 reading drop a few points in the cold?

A: A small drop is normal due to vasoconstriction reducing fingertip blood flow. Unless it falls below 92% or so, it’s likely still within the normal range.

  • Q: What should I do if moisture or liquid gets inside?

A: Power it off immediately, remove batteries, blot any moisture with a cloth, and place it in front of a fan. If it still doesn’t work after thoroughly drying, contact Masimo support.

  • Q: Can I just stick it in the microwave to warm up quickly?

A: Absolutely not! Microwaving will fry the internal circuits. Always warm the device slowly to room temperature.

Bundling Up Your Rad-57 for Winter Use

I don’t know if you’ve noticed, but our trusty Rad-57 isn’t dressed for full-on winter weather. No hat, scarf, or mittens to be found!

So when I head out into the cold with it, I make sure to bundle it up properly so the old thing doesn’t catch a chill. Here are my tips:

  • Tuck it into an inside jacket pocket close to your body.
  • Put it in a small zip-top plastic bag if snow or rain is coming down.
  • Make sure your hands are warm before using uncovered fingers.
  • Keep the battery area dry and free of moisture.
  • Bring it back indoors regularly to warm up.

I know it sounds silly to baby a piece of electronics. But keeping it protected from the elements helps avoid issues to begin with. I aim to provide a toasty micro-climate for my rad Rad-57!


Pampering Your Pulse Oximeter

You know how they say an ounce of prevention is worth a pound of cure? Well, the same goes for the Rad-57.

Giving it a little TLC between uses helps reduce problems when old man winter comes to town. Here are some of my device-pampering tips:

  • Keep it stored at room temperature when not in use.
  • Replace batteries regularly even if not fully drained.
  • Clean with a soft cloth and avoid abrasives.
  • Don’t drop it! Those impacts can throw off calibration.
  • Check buttons and ports periodically for damage.
  • Keep the battery contacts clean and dry.

I know, it seems like a lot of babying for a gizmo. But preventative care pays off by minimizing issues down the road. A well-cared-for Rad-57 will thank you!

How Other Oximeters Stack Up?

Lots of folks wonder how the Rad-57 holds up against other pulse oximeter models when it comes to use in the cold. I’ve tested a few alternatives myself.

Overall, the Rad-57 seems to outperform competitors when you get into frigid temps. Reasons why:

  • Its low perfusion readings stay more accurate when blood flow is down.
  • The algorithms are less impacted by shivering/motion.
  • It reliably reads lower SpO2 levels compared to some models.
  • The buttons and screens remain responsive even in extreme cold.

Not saying other options are terrible by any means. However, the Rad-57 was built for resilient operation in challenging environments. If you’re dealing with cold conditions regularly, it’s worth the investment.

Let me know if you’ve had good or bad experiences with other models in winter. I’m always curious to hear how the brands compare.

Additional Troubleshooting Resources:

Hopefully, the tips in this guide get your cantankerous Rad-57 detector to cooperate again! But if you need more troubleshooting information, a few handy resources:

More Related Fixing Guides:


Brrr, it’s cold just thinking about troubleshooting pulse oximeters in freezing temperatures! But I hope these practical tips help you keep your Masimo Rad-57 up and running through even the most frigid conditions.


With some knowledge and preparation, you can outsmart the cold and keep your vital signs in check all winter long.

Stay warm out there and breathe easy! Let me know if you have any other tricks for using these finicky devices in the cold.

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