Why did my Vitamix blender shut off? Understanding motor heating (with data)

measuring-vitamix-motor-temperatureIf you’ve ever had your Vitamix blender abruptly stop working, most likely it was the thermal override kicking in. The thermal override turns the motor off before the motor burns out. Then, once the motor cools, you can run it normally again. It’s not a huge deal, but it’s best to avoid. (Depending on what kind of blending you do, you could easily use a Vitamix for decades without ever getting close to overheating. But, if you blend super thick foods, there’s a good chance it will happen at some point.)

If you have an Ascent or Venturist model, it will display error code E31 or E3x when the thermal override activates.

This post will explore what causes motor heating and describe how to minimize it. I investigated by directly measuring the temperature of the motor in a variety of blending conditions.

Why should you avoid overheating the motor?

  • If the thermal override trips, you cannot run the Vitamix until it cools, which can take 20–60 minutes. If you’re in the middle of making something, the interruption is a hassle.
  • Keeping the motor cooler should prolong its life. Occasionally overheating the motor is fine, but if you do it regularly, it puts more wear and tear on the motor.

If you don’t want to read all the details, here are a few key points:

Why did my Vitamix shut off?

Thick blends can overheat the motor. It will shut itself off before it burns out, and it will not let you turn it on until it cools down. To avoid overheating, don’t blend more than 4 cups of thick blends like hummus, nut butter, or ice cream. When blending thick ingredients, run at maximum speed.

If the motor does overheat, you can use it again sooner by blowing air into the vents with a fan or hairdryer (on cold!). Some people speed cooling by putting the Vitamix base in the fridge, but, if you leave it in too long, you could run into condensation issues when you take it out.

The rest of this post will explain factors that contribute to motor heating, why fast speeds are helpful, and a special motor-cooling trick.


Vitamix motors have the following properties:

  • The harder the motor works (e.g. with a thicker blend), the more it heats itself. This is because it draws more electric current at higher loads. (The amount of current draw has to do with the back EMF that forms in the motor.)
  • Thicker blends slow down the motor (see my speed measurement page for more details). This is why the motor sound has a lower pitch when blending thick things.
  • The motor is cooled by air blown by a fan on the bottom of the drive shaft, and the fan spins at the same speed as the motor.

You can see how a thick blend increases the chances of overheating: the motor heats more and has less cooling. For more information about the type of motors used in Vitamix machines, look up universal motors.

Factors that contribute to motor heating

You don’t need to obsess about these factors—just keep them in mind. The motor is most likely to overheat when multiple factors act together.

  • Thickness of blend (thicker = more heat).
  • Quantity of blend (more volume = more heat).
  • Blending time (longer time = more heat). You can get away with blending something really thick for a short time, but if you blend it for extended periods, it will overheat the motor. Similarly, if you make one recipe after another, the motor can be more likely to overheat, because it didn’t fully cool between uses.
  • Temperature of environment (hotter environment = less cooling by air) so you have to be more aware in the summer or if the kitchen is hot from a lot of baking.
  • Interestingly, humidity of the air does NOT matter.1

That brings us to motor speed, which I think is most interesting. Most Vitamix manuals have a statement like this one from the 7500 manual:

Tip: Blending too long at too low of a speed setting will overheat the machine and cause the Automatic Overload Protection to turn off the machine. Blending on higher speed maximizes the motor’s cooling fan to avoid overheating.

(Many people repeat a version of this and say that the cooling fan only runs when the Vitamix is set to high. But that is not true. The fan is connected to the motor shaft, so it runs every time the motor does. If you put your hand near the air outtake vents on the bottom sides of the base, you can feel air at all but the slowest speeds, where it is still blowing, but is less detectable.)

Vitamix’s speed recommendation is counterintuitive, and it inspired me to investigate by directly measuring the motor temperature.


I attached a small temperature probe to the motor stator with thermally-conductive double-sided tape, plus temperature-resistant tape over it to be on the safe side. I ran the wire out an air vent and recorded temperature over time using an Arduino.

I made a batch of 8 cups of thick syrup (similar to what I used for my horsepower measurement) to get a high load that would be consistent. One thing to watch out for with syrup is that its viscosity changes significantly with temperature, and it heats up during blending. But as long as you keep this in mind, you can ensure the syrup temperature is consistent across comparisons.

Here’s a simple temperature trace of the motor blending thick syrup for 1 minute, and then staying off:

blend-heavy-load-in-vitamix-then-let-cool-temperature-plotYou can see that it’s about halfway cooled after half an hour and almost completely cooled after two hours, but it takes about 8 hours for the motor to fully return to its starting temperature. The important takeaway is that motor heating becomes a more significant issue if you blend multiple thick things within about an hour, because the motor won’t have time to cool in between. [Curious why there is a bump at ~105°F?2]

I wondered if lower speeds would heat more due to the slower cooling fan, which would explain Vitamix’s high speed blending recommendation. So I made a series of measurements comparing motor heating at high and low speed. However, for a given load, high speed always heated the motor faster than lower speeds. This seems contrary to Vitamix’s recommendation! At first I thought maybe I wasn’t seeing the lower speeds heat more because the motor was too close to room temperature. (The greater the temperature difference between motor and air, the greater the cooling advantage of higher speeds.) So I made measurements at elevated motor temperatures, but again saw the same thing: high speed heated the motor more than low speed. This means that the lower electric current at lower speeds more than compensates for the slower cooling fan.

Then I realized that in most actual thick blending situations, the Vitamix does not run against a constant load. When making hummus or nut butter, the motor encounters a high load, and then the blades often form an air pocket. In the air pocket the blades encounter almost no resistance. Then you collapse the air pocket with the tamper, so the motor ends up going between high and low loads.

I figured maybe the air pockets only form at high speed. I tested with a batch of almond butter that was identical to my recipe write-up, except I blended it at low speed (setting 2 of 10). Sure enough, no air pockets formed at low speed. Here are the temperature plots:


The initial motor heating rate at low speed is less than at high speed. At that point the blades are chopping the nuts. But at high speed, as the nut pieces get tiny, they fly away from the blades and form an air pocket, and the motor starts cooling more. The low speed case ends up heating much more than the high speed one. (Also, the low speed almond butter never got fully smooth.)

This is the answer to the paradox of why high speed keeps the motor cooler. At high speed the blade is more likely to form air pockets, which allow the blade to intermittently spin at low load, which keeps it much cooler. (You can tell when the motor forms an air pocket because the sound changes to a high pitch whine.) There’s also a secondary aspect, which is that at high speed the motor will be able to finish the blending task faster, so it’s on for a shorter time.

The use of air pockets to cool the motor is a feature of Vitamix blenders that I didn’t know about until now. (The formation of an air pocket is not a problem because Vitamix machines come with a tamper that lets you collapse it without needing to stop the motor.) Now I’m wondering if Vitamix engineers designed the blades to form the air pocket for this purpose.

Advanced cooling trick

You can use this trick if you have a thick blend that is not forming air pockets or if you can sense the motor heating up. Sometimes you can smell the motor heating before the thermal override kicks in. (I noticed the motor smell when the windings got to ~167°F, and the thermal override kicked in at ~185°F.)

The trick is simple: stop the motor, remove the container, make sure that nothing is touching the drive socket, then turn the motor on high. Run it for ~60 seconds, and it will pull lots of air through without having to work hard.3 Just make sure nothing touches the fast-spinning drive socket. And remember to only move the container when the motor is fully stopped. Here’s a comparison of the motor cooling while turned off and cooling with 1 minute running with no container:


In this case, 1 minute of no-load blending cools the motor as much as waiting ~30 minutes without running. You can see the temperature quickly drops almost all the way to room temperature when running without the container. It increases after the motor stops because the thermometer measures the surface temperature of the windings. The temperature increase comes from conduction from the hotter internal windings.

One thing to watch out for is that the thermal override sensor also sits on the surface of the windings. So if you use this trick and immediately resume super heavy blending past the overheat temperature, the thermal override will be a bit delayed, and the motor could go above the ideal temperature cutoff. It shouldn’t be a problem if you wait a few minutes after the no container blend, or if you’re blending something only moderately thick. Also, if you use the trick preemptively, you can prevent the motor from getting close to the overheat temperature.


Thick blends cause blender motors to work harder, which makes them more likely to overheat. If you understand the basics of what’s going on, you can make thick blends without overheating. Running the motor at maximum speed reduces the chances of overheating by shortening blending time, and by periodically forming an air pocket around the blades, which allows the motor to efficiently cool itself. There’s one other thing I learned from these measurements: you don’t have to be paranoid about totally avoiding low speeds for thick blends—low speed will usually only be a problem if you leave it blending for extended periods over ~1 minute.

1. Interestingly, the heat conduction properties of air are not significantly sensitive to humidity.
I was surprised by this because, as humans, humidity influences our perception of temperature. But, apparently, that’s mainly due to confounding factors and clothing being less warm when it’s damp.

2. It doesn’t matter for this discussion, but I’m afraid the bump may be distracting. It is a repeatable feature of these temperature plots, and I think I know what causes it. Above that point the motor is hot enough that the other parts inside the base warm up as they absorb heat from the motor faster than they lose it to the environment. That bump is the point where the motor temperature has roughly equilibrated to the inside of the base. That temporarily slows the motor’s cooling rate. Then the rest of the base starts cooling, and the motor resumes its cooling.

3. For every combination of speed and load, there is a steady-state temperature that the motor would get to if you kept blending long enough. At that temperature, heat from the current in the windings is balanced by cooling by the fan. For high loads, that steady-state temperature is well above the overheat temperature. I measured the steady-state temperature of the motor at max speed with no container, and it runs about 14°F above ambient, which is much less than the overheat temperature. The current draw at maximum speed with no container is 2.6 A, compared to 12-15 A for high loads.

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Why did my Vitamix blender shut off? Understanding motor heating (with data) — 54 Comments

  1. Fair enough. I see your point, and I’ll make a minor edit. I was initially going to mention some properties specific to universal motors (high starting torque, voltage dependence), but ended up cutting those because they were not essential for understanding the rest of this piece.

  2. Thank you! I have owned/used my vitamix for close to 10 years and have just recently noticed a burnt smell and it stopped in the middle of blending chia pudding today. Good to know it is a protective feature and not a broken motor! Will remember the trick of running motor with no fill vessel on top to cool it. Good advice!

  3. Excellent Post and research regarding overheating and cooling of the Vitamix motor. We’ve had ours about 2.5 years and it just started shutting off lately. I randomly discovered that it wasn’t totally burnt out, by trying it again after a couple of hours. My questions to you are –
    1. Do you feel the wearing of the bearings in the armature, and the wearing of the brushes after a few years of use have any effects on how soon the motor will begin overheating?
    2. Do you feel the capacity of the motor is properly sized given the capacity of the large container, especially since they include the plunger and strongly advertise the ability to pulverize fibrous vegetables and other ingredients, seeds especially, into healthy smoothies? I can give you information on why a smoothie should be thicker rather than thinner if you care to know…

    • 1. I’ve never heard of either of those being a problem with Vitamix machines. If you are really worried, you can check by gently turning the drive socket with your fingers when the machine is off, and it should be possible to turn it. Something that does occasionally fail is the bearings of a container, which you can test by gently turning the gear on the bottom. (If you can’t turn it with your fingers, you’ll need a new one.)

      2. I do think the motor is sufficient, though if you are making full containers of thick smoothies you do have to be more aware of best practices.

      That said, if your motor is regularly shutting off and it’s only 2.5 years old, you might want to call up Vitamix. Your machine is still under warranty, and they will check it out and repair any problem for free.

  4. Hi. Great post!!
    I have a question for you.
    I make cashew cheese and its starting to get serious. A lot of blending lately. And my Vitamix often shuts down.
    I was thinking in attaching a 10 or 12mm fan.
    I don’t know exactly where I would put it. I thought inside the case, but I never opened before, so I don’t know if would fit in.

    Do you think that would help? Could it happen to only cools the sensor of the Overload and inside would still be hotter?


    • I do not think you would find a good space for an extra fan inside the case. Even if you could fit it in there, I would be concerned that it would disrupt the airflow more than it would help. And you are right that the fan would cool the surface more than the inside, so the overheat sensor would be less effective.

      Have you tried the various tips covered in the post?

  5. Thanks for your thorough scientific advice. My Vitamix shut down for the very first time today. I was making smoothie bowls with lots of frozen fruit + 1 frozen banana. From what I read here, the mixture was too thick and the motor overheated. I will wait an hour and let it cool down. Thanks again! Julie

  6. Big thanks for publishing this piece! It’s great to see real data behind the instructions, because “the motor stays cooler when it runs faster” is deeply counterintuitive.

  7. Thank you for sharing your experiments, we found them intelligent, well articulated and very useful. We have a 21 year old Vitamix which has had heavy use all those years. Today for the first time ever, we smelled a burning smell. I’m going to run the hair dryer on cold down into the motor to help it cool down. At the moment the motor is making a strange revving noise from speed 1-7. From 7-10 and then to HIGH, the motor runs as usual but the smell quickly starts. We were blending a thick mixture of cashews, rice syrup, coconut oil. We have noticed it has been losing power over the past few months. Does that sound like a repair job?

    • It sounds like a repair may be in order.

      The revving is likely caused by a relatively common issue with old Vitamix machines. The variable speed knob is connected to a potentiometer, which eventually stops responding smoothly due to wear/dirt/corrosion.

      Since your machine is out of warranty, it might be worth trying to take care of yourself. Vitamix would refurbish your machine for you, but, last I heard, out-of-warranty repairs start at $150. If you or someone you know feels comfortable taking things apart, it’s not too bad. You can search for instructions online. Replacement potentiometers are relatively cheap, and, in many cases, you can just use some electrical contact cleaner on the one you have.

      I don’t know if your motor has a separate problem that is causing it to overheat. It’s possible that the thick mixture plus the plus the faulty variable speed control are the only problem. Or there could be something else going on. When you say it’s been losing power, does that include when it is set to HIGH? If so, then there may be a deeper problem with the motor, and an official servicing could be worth it.

  8. I was chopping brussel sprouts on low speed when the motor stopped.It worked on high speed only. Thinking that the thermal override kicked in, I let it sit and checked it by putting it on low speed every 30 minutes. Still did not work on any low speed, only high speed which tells me that the on/off switch works. I let it sit for 2 days and still no low speed. Also tried a manual thermal reset by placing it firmly down with no results.Is it possible that the variable speed switch might have gone bad. Usually when that occurs, you get erratic speeds between 1 and 5 but the motor still turns on.The only other thing I can think of is the thermal override switch will not reset because it is burnt out. What is your opinion?

    • The thermal override will keep it from running at any speed (including high), so your problem is not from overheating. You are right that the most common issue is the variable speed knob going wonky, but it sounds like you have a less common failure mode. It could be a simple issue of the variable speed switch dying, or it might be a more complicated issue of a control board failure. If your machine is under warranty, Vitamix will take care of it for free. If it’s out of warranty, it might be worth having someone who is comfortable taking things apart open it up and do some connectivity checks.

  9. Adam
    I replaced the control board which solved the problem of running in variable speed and high. BUT…it has only one speed which is the highest of the variable speeds. The high speed switch does make it a little faster. What are the odds that the control board and the variable speed potentiometer went bad at the exact same time? Can the control board cause that problem also. I could only find a rebuilt one for that machine. They said it was tested and OK.

    • I don’t know. I think it’s unlikely that your problem is with the potentiometer, because the typical problems develop over time, and the behavior is that on variable the speed jumps around. My guess would be that it’s something to do with the control board; possibilities include: it’s faulty, it’s not hooked up properly, or it’s not the right one for your model. Sorry I don’t have a clear answer for you.

  10. For anyone interested in the humidity thing, the reason humid air feels warmer to humans is due to evaporative cooling. When moisture on your skin evaporates into the air the phase change from liquid to a gas consumes heat energy which has a cooling effect on your skin. Even if you’re not profusely sweating moisture is evaporating from the surface of your skin (we are after all 70% water). When the air around you is more humid, the evaporation of water slows, when the air is less humid it increases. This is a significant method of cooling which is very strongly influenced by the airs humidity levels. In the case of a motor winding, they are usually just copper which wouldn’t benefit from evaporative cooling so air humidity levels have no effect. If you were to waterproof the windings and mist them with a constant supply of water, you would find the air humidity levels would then have an effect on their cooling rate.

  11. I have an old Vitamix which has recently tripping quite frequently at the outlet. On examination, it does not appear the thermal override tripper does not work. If so, can I replace it. How do I do it

  12. Thanks so very much for your prompt reply and suggestion.

    To explain the problem, I have a really old 30+ years Vitamix 3600Plus. It has been working wonderful all these years. A few times, we have found that the thermal protector switch trips but promptly goes back to position after we click on it. Recently I have noticed that the Vitamix has tripped at ground fault circuit breaker at the switch. On examination of the thermal protector (on the side), I notice it does not go back to its normal position making me suspect that might be the culprit for the tripping at the switch. I hope this explanation gives you a good idea about the problem.

    I have two concerns:
    1. Will the replacement thermal protector you have suggested fit this old Vitamix?
    2. How do I dismantle the old protector and install the new one?

    I will very much appreciate your help.


    Dave Devarajan

  13. I have a Vitamix Professional Series 750.
    The mixer is overloaded … the power does not turn on after a few days.
    Where does the Professional 750 have a reset button?
    There is no reset button on the bottom.

    and …Does anybody know what part is broken?
    Thank you.

  14. Hi
    My Vitamix is sluggish and keeps blowing my fuse in the plug, stopping it from working. Has anyone got any ideas what this could be? It works for about 10 minutes once the plug fuse is changed and then blends but if I leave it on for 5 minutes and start to heat the ingredients to make soup it blows the fuse, it’s happened twice on consecutive days.
    Any help greatly appreciated as it’s just out of warranty, happy to do the repairs ourselves if we know what to replace!
    Thanks everyone.
    Best wishes

    • It’s possible that the fuses are just not up to the level of current that the Vitamix draws. Or if something else is on the same circuit, that could put it over the top. However, if it used to work fine with the same type of blend, then that suggests something may be wrong with the motor. And I’m not sure what you mean by sluggish, but if it seems weaker than it used to be with identical ingredients, that’s another bad sign. And if something’s wrong with the motor, I don’t think there’s an easy fix.

      You can check to make sure the bearings in motor are still good by gently twisting the drive socket with no container on and with the machine off. It should turn with a fair amount of resistance. And gently twist the gear at the bottom of the container. It should be relatively easy to turn (but not spin freely), and shouldn’t make any grinding noises.

  15. Hi,
    I have a refurbished Vitamix 5300 and it was working fine for a year. Yesterday we made a large amount of thick soup and it suddenly stopped working. Thinking it got overloaded and overheated I waited for almost 12 hours. But it still switches on the blue light; but when I try to pulse or start it, the blue light just blinks once and nothing happens. the motor wont start. Anything I can do ?

    • If it’s still not coming back on after 12 hours, it’s probably not going to come back, but I’d say wait another 12 hours before you completely give up on it. The good news is that if it’s just a year old, it’s still covered by the warranty. Call Vitamix (800-848-2649) and they will take care of it for you for free.

  16. Thanks for the excellent post. Mine stopped working with no electric , “burning motor” aroma. I wondered if an auto shut-off kicked in.

    Reading this, I was running the blender in low while making a veg broth concentrate so it makes sense since I’ve blended other thick things and not had this happen. I had the motor on high in those runs.

    Thanks for doing the work and sharing the graphs. Nice to see some science applied to the problem.

    I’m a fellow scientist. Chemist turning computer scientist. Kudos on the write up. And it’s nice to know my blender isn’t maimed forever.

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