# How I "fixed" my Thermapen that wasn't broken



## johnmeyer

I'm posting this just so someone who encounters the same thing doesn't waste time contacting Thermapen or trying to fix something that isn't actually broken. The symptoms don't fit the what you would normally expect from what actually caused the problem, so you might be tempted to do the wrong thing.

Here's what happened.

About three years ago, the on/off switch in my Thermapen (it gets activated when you open the probe) malfunctioned. I contacted Thermapen and they replaced it under warranty.

Then, several months ago, it appeared to be doing the same thing, but this time it was intermittent. I would open the probe, and I would get no display. I then closed and then re-opened the probe, and this time it would work. When the switch malfunctioned, it just quit working. However, I thought perhaps it was a variation of the same problem.

Over the ensuing weeks, after this first started to happen, the number of open/close operations required to get the thing working again kept increasing. Since I'd had experienced that switch failure three years ago, all I could think was, "oh darn, here it goes again, and this time it won't be covered under warranty." I figured I was going to have to spend $100 on a new one.

However, I figured I should at least check the batteries, even though this didn't feel like a battery problem and even though Thermapen guarantees the batteries for 1,500 hours of operation (see below: I was two orders of magnitude short of that figure). Since I am a geeky engineer, I have a dedicated battery tester that tests batteries under load and provides exact voltage measurements. The Thermapen is powered by two 2032 primary cell (i.e., _not_ rechargeable) "coin" batteries. When fresh, they should generate a little more than 3.0 volts.

Mine both measured at under 1.0 volt!

So, that was the problem. Even though it didn't "feel" like a low battery, that is what it was. According to Thermapen, this shouldn't have happened at all because the batteries are rated at 1,500 hours. I use my thermometer once a week when making yogurt and for all other uses it probably also averages out to once a week. So, it is on and off perhaps 100 times a year. In three years since I got the replacement that would bee 300 times I've used it. I often forget to close it, so it times out after five minutes. Even if it always was left to time out, my usage over the past three years comes to 300 x 5 = 1,500 minutes. That's 1,500 _minutes_, not 1,500 _hours_. These batteries should not have failed, but they did.

So, at least with my unit, the batteries ran out _much _sooner than what Thermapen predicted, and the battery failure symptoms were not at all what I was expecting.

My purpose in posting this is to help those of you who might experience similar problems.


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## dr k

johnmeyer said:


> I'm posting this just so someone who encounters the same thing doesn't waste time contacting Thermapen or trying to fix something that isn't actually broken. The issue is that the symptoms don't fit the what you would normally expect from what actually caused the problem.
> 
> Here's what happened.
> 
> About three years ago, the on/off switch in my Thermapen (it gets activated when you open the probe) malfunctioned. I contacted Thermapen and they replaced it under warranty.
> 
> Then, several months ago, it appeared to be doing the same thing, but this time it was intermittent. I would open the probe, and I would get no display. I then closed and then re-opened the probe, and this time it would work. When the switch malfunctioned, it just quit working. However, I thought perhaps it was a variation of the same problem.
> 
> Over the ensuing weeks, after this first started to happen, the number of open/close operations required to get the thing working again kept increasing. Since I'd had experienced that switch failure three years ago, all I could think was, "oh darn, here it goes again, and this time it won't be covered under warranty." I figured I was going to have to spend $100 on a new one.
> 
> However, I figured I should at least check the batteries, even though this didn't feel like a battery problem and even though Thermapen guarantees the batteries for 1,500 hours of operation (see below: I was two orders of magnitude short of that figure). Since I am a geeky engineer, I have a dedicated battery tester that tests batteries under load and provides exact voltage measurements. The Thermapen is powered by two 2032 primary cell (i.e., _not_ rechargeable) "coin" batteries. When fresh, they should generate a little more than 3.0 volts.
> 
> Mine both measured at under 1.0 volt!
> 
> So, that was the problem. Even though it didn't "feel" like a low battery, that is what it was. According to Thermapen, this shouldn't have happened at all because the batteries are rated at 1,500 hours. I use my thermometer once a week when making yogurt and for all other uses it probably also averages out to once a week. So, it is on and off perhaps 100 times a year. In three years since I got the replacement that would bee 300 times I've used it. I often forget to close it, so it times out after five minutes. Even if it always was left to time out, my usage over the past three years comes to 300 x 5 = 1,500 minutes. That's 1,500 _minutes_, not 1,500 _hours_. These batteries should not have failed, but they did.
> 
> So, at least with my unit, the batteries ran out _much_ sooner than what Thermapen predicted, and the battery failure symptoms were not at all what I was expecting.
> 
> My purpose in posting this is to help those of you who might experience similar problems.


I'm not sure but the new Thermapens maybe alkaline batteries which are better in cold weather. I have a Thermowand now called the Javelin with a coin 3v that is rated for 5,000 hours. It won't make it. The batteries shelf life will expire first. Good idea to check the battery voltage. 
-Kurt


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## dward51

Ah Ha!!!!! Mine has been doing this occasionally lately.  I'll check the batteries.  Thanks


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## SmokinAl

I have had to replace the batteries in mine as well.

Al


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## mdboatbum

Thank you so much for posting this!! Mine has been doing the same thing.


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## one eyed jack

Thanks for your heads up.  It will reduce my panic if mine starts acting up.


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