# MES40 2.5 loss of temperature control - any idea what the problem is?



## uncle eddie (Apr 28, 2018)

First - all external and meat probe thermometers are calibrated - that is definitely not the issue here.

My MES40 has been running hot for a good while, but I was OK with a "fast" 275F smoker.  Now it is getting into the 300F-310F range when set at 220F or higher.  When I set it at 215F or lower, it seems to hang around 235-240F.  Those are my two temps now - 237F +/- or 305F +/-.  I have lost all confidence in set and forget - the reason for an electric smoker.

HOWEVER - I called Masterbuilt and they told me they thought it was the temperature limit switch, which is built into the smoker and can't be replaced...is this true?  I looks like it might be.  I have cleaned it well and this did not help with the temp control issues.

I have replaced the meat temperature probe 2 or 3 times and the control panel once on this smoker - all very easy repairs.  I am not electrically inclined but can change a breaker, light fixture, light switch. 

Any help is appreciated.


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## tag0401 (Apr 28, 2018)

You would think a temp limit switch could be replaced. Hope you get it resolved, wish i could be of more help


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## mosparky (Apr 28, 2018)

Not sure what the problem is exactly, but I highly doubt the temp limit switch. It is there strictly as an over temp safety limit. If there is a failure that would otherwise cause a run-away heat situation, it should open the element circuit at approximately 300 deg. after cooling a bit it will close and heating will continue until the 300 deg mark is again attained and open again..so on and so forth. I'd bet it is the only thing at the moment keeping it from exceeding the 315 deg mark.
 That said, it is sounding like either the micro processor unit has lost it's mind or the temp sensor ( more likely ) has or is failing. I don't think this is a readily replaceable device on any model MES. You would have to remove the entire outer case to get to it and the wires that run to the control panel on the top or "make" an access hole.
 If you can get Masterbuilt to send/sell you one, you might be able to carefully measure the back panel and cut out an access panel to get to the sensor and replace it. You would have to splice it to the existing wires and fashion a new cover plate for the hole. You can see the sensor in about the middle of the back wall from the inside. It is a relatively small nub about 1/4 in in dia i think. The temp limit switch is to the left side of the back wall and about 1/2 dia.
 This is the point where many would decide to trash it or Rewire for PID control. 
Any chance moisture has gotten into the control panel ? Even condensation could wreak havoc. The effects could be temporary or permanent depending on where and how.


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## uncle eddie (Apr 28, 2018)

Thnx for your explanation mosparky - More stuff to ask Masterbuilt about on Monday.

Moisture could have gotten into the control panel as the unit is outside and sometimes heavy dew can get on it.  It is under a MB cover (mostly), but not when cooling and it is under a roof overhang - but not good enough to keep it dry in bad weather with a little wind.

I will look to see if I have another control panel.  For some reason I think I might have one still.  And at this point it wouldn't hurt to swap it out.  ((When I order parts - I usually get more than 1 as their shipping charges can get expensive.))

If it is one of the built in parts...to the dumpster it will go.


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## mosparky (Apr 28, 2018)

It would be great if you could keep us posted on the results. Others will wvwntually have similar issues. I think some already have. Sure would like to show them not all is lost.


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## uncle eddie (Apr 29, 2018)

mosparky - I will do so.

So - just because I am stubborn - I am going to try to smoke ribs on it today using my AMNPS for smoke, of course.  I am turning on the smoker to 210F (shooting for the 237F +/-) about 2 hours early because it takes a while for the temp to stabilize in it's current state of rebellion.  When we get back from church, I will see if I will be smoking on my MES40 or my ancient Brinkman, built-like-a-tank charcoal/stick smoker.


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## daveomak (Apr 29, 2018)

The high temp limit can be changed out...  There are a couple threads on it...  
I call it a snap switch..  others have a more technical name for it..   It is the round button on the back wall of the smoker....


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## daveomak (Apr 29, 2018)

https://www.smokingmeatforums.com/threads/masterbuild-not-heating.273201/#post-1804243

https://www.smokingmeatforums.com/threads/open-up-an-mes-gen-2-5.269948/#post-1769117


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## dr k (Apr 29, 2018)

Mosparky is on the same page as myself. It's over heating vs. Underheating. Dave mentioned its a safety snap disc switch so it does reset after the temp drops but that isnt what's happening. Your problem is exactly as your thread is titled. That toggle shaped Mes sensor that has no access panel or control board/controller is defective.


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## Bearcarver (Apr 29, 2018)

Sounds more like the controller problem to me, but what do I know.

Bear


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## uncle eddie (Apr 29, 2018)

I appreciate all of your input - I have plenty to discuss with Masterbuilt tomorrow.  I will let you all know the results.

FWIW - setting the smoker on 210F is holding pretty close to 230-235F without massive temperature spikes.


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## Bearcarver (Apr 29, 2018)

uncle eddie said:


> I appreciate all of your input - I have plenty to discuss with Masterbuilt tomorrow.  I will let you all know the results.
> 
> FWIW - *setting the smoker on 210F is holding pretty close to 230-235F without massive temperature spikes.*




If that was a regular thing, that would be good!!

Bear


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## uncle eddie (May 1, 2018)

Just hung up with Masterbuilt Customer Service - they were awesome again

I was put on hold for about 5 minutes while they researched the problem and they decided that they were going to replace - free of charge - the high temperature limit switch ($8.XX part plus shipping).  I should have it in a few days.  

I did ask if this will require drilling rivets and such and they said - no - it was a simple repair.  I will let you know in a few days.


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## Bearcarver (May 1, 2018)

uncle eddie said:


> Just hung up with Masterbuilt Customer Service - they were awesome again
> 
> I was put on hold for about 5 minutes while they researched the problem and they decided that they were going to replace - free of charge - the high temperature limit switch ($8.XX part plus shipping).  I should have it in a few days.
> 
> I did ask if this will require drilling rivets and such and they said - no - it was a simple repair.  I will let you know in a few days.




That's Great !!
Hope that does the Trick!!

Bear


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## biteme7951 (May 1, 2018)

The Limit switch is a safety switch to cut off a main controller that doesn't regulate the temperature properly. The new limit switch will eliminate the massive overrun, but will not help to maintain the set temperature.. just the runaway control. try the new switch but your main temp controller is suspect.

Barry.


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## uncle eddie (May 1, 2018)

I agree - but I can't say no to a free part/shipping.  I am thinking this repair is likely to be a 2 step process.


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## daveomak (May 1, 2018)

Eddie, morning...   The description of your problem is typical with an "over limit" temp switch failure...  I think you will be pleasantly surprised with the fix...  I previously posted what others experienced in the change out....
Dave


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## uncle eddie (May 5, 2018)

still waiting on parts....


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## uncle eddie (May 11, 2018)

I called Masterbuilt up because the part was supposed to be shipped a week ago last Monday...had not arrived yet.  TODAY they said the part would not be available until June...not June 1...just June.

Masterbuilt gets a demerit today.  This is the first time customer service has let me down.

As least I still have 2 temps on my MES 40 - 235F +/- and 310F +/-...it is still usable.


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## Bearcarver (May 11, 2018)

That Sucks!
Especially when you aren't even sure those parts will solve the problem.
I'm hoping for the best.
I was hoping they would just give you a new Smoker, which they sometimes do.

Bear


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## Nutshell (May 14, 2018)

uncle eddie said:


> I called Masterbuilt up because the part was supposed to be shipped a week ago last Monday...had not arrived yet.  TODAY they said the part would not be available until June...not June 1...just June.
> 
> Masterbuilt gets a demerit today.  This is the first time customer service has let me down.
> 
> As least I still have 2 temps on my MES 40 - 235F +/- and 310F +/-...it is still usable.


I ditched the factory controller and just went with an Auber PID.  Works amazingly well.


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## SonnyE (May 14, 2018)

First, Mosparky has the limit switch covered exactly. It has nothing to do with actual temperature control. It is there to prevent the smoker from running into over temperature, which could cause a fire.
An automatic over-temperature shut down.
Your lack of temperature control has to do with
A. The temperature controller on top.
B. The actual control board with the relay that turns the element on, or off.
Specifically, the relay may be failing in the closed position, allowing irratic temperatures, and also bumping it against the High Limit switch which shuts it off.
But the high limit switch is not a precision device. It is an approximate temperature limiting switch.
It's a pity you have not spoken to someone more knowledgeable at Masterbuilt, and makes me wonder about their service in general. After all, there is not that much that can go wrong with their smokers.
But whoever it is feeding you information should not be. In mine, the limit switch is screw mounted. So it could be removed.
One bad sign is anytime they have to put you on hold, they don't have the answer and are asking someone else, thumbing through a manual, or coming up with something to get you to go away. You may have been talking to a janitor who happened to be close to the phone.

You can get it fixed, and I would not throw it away. I would get an external (Auber) control, bypass the Chinese electronics, and let the goodness be delivered. But that's just me.

Or, you could throw it my way. And I'll fix it.... :confused::p:rolleyes:


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## tallbm (May 14, 2018)

Here is a post I put together for an MES Rewire to be used with a PID Controller like the Auber Plug and Play PID.
If Masterbuilt fails to come through for you then you have this rewire and PID Controller option that will make your MES easy to work on and keep running for many years unless it get's into a car wreck :)

https://www.smokingmeatforums.com/threads/mes-rewire-simple-guide-no-back-removal-needed.267069/


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## Nutshell (May 14, 2018)

tallbm said:


> Here is a post I put together for an MES Rewire to be used with a PID Controller like the Auber Plug and Play PID.
> If Masterbuilt fails to come through for you then you have this rewire and PID Controller option that will make your MES easy to work on and keep running for many years unless it get's into a car wreck :)
> 
> https://www.smokingmeatforums.com/threads/mes-rewire-simple-guide-no-back-removal-needed.267069/


This is a fantastic write up.  I completed mine start to finish in 30 minutes (2 beers)!!!


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## uncle eddie (Jun 3, 2018)

My part is supposed to be here in "June"

It is June 3...

We'll see how true Masterbuilt is to their word.


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## Nutshell (Jun 3, 2018)

uncle eddie said:


> My part is supposed to be here in "June"
> 
> It is June 3...
> 
> We'll see how true Masterbuilt is to their word.


I can tell you first hand, they will follow through and make it right but they are beyond painful to deal with.


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## tallbm (Jun 4, 2018)

Nutshell said:


> This is a fantastic write up.  I completed mine start to finish in 30 minutes (2 beers)!!!



Thanks!  
Once you have a PID setup and the numbers are tuned in, things are heaven!


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## Bearcarver (Jun 4, 2018)

Karen Adler said:


> I love Masterbuilt Smoker. They are very good for smoking !




I agree, and I've been using MES Smokers for 9 years.
Love-em!!

Bear


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## uncle eddie (Jun 26, 2018)

The part came today so Masterbuilt Customer Service came through again...although I would have appreciated knowing a date other than it will be here in "June"

The part they sent is a High Temperature Limiter.  It is raining or I would try to put it in tonight...looks like a Saturday project now and looks to be fairly straight-forward


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## mosparky (Jun 26, 2018)

Dang...they just barely made it in June. I was beginning to think you forgot about this thread. I really want to see if this fixes things.


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## tallbm (Jun 26, 2018)

uncle eddie said:


> The part came today so Masterbuilt Customer Service came through again...although I would have appreciated knowing a date other than it will be here in "June"
> 
> The part they sent is a High Temperature Limiter.  It is raining or I would try to put it in tonight...looks like a Saturday project now and looks to be fairly straight-forward



Do you have a picture of this thing?  I wonder if they just sent you a new safety rollout limit switch.  If that is the case then I think they never really addressed the problem and now your smoker is going to cut out for a period of time when it over heats rather than "control" the temp.  

I hope this is not the case.


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## uncle eddie (Jun 27, 2018)

I will snap a pick this evening...


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## Bearcarver (Jun 27, 2018)

I'm still hoping it works out real good for you Eddie!!

Bear


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## uncle eddie (Jun 28, 2018)

Here is the part they sent to me...


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## tallbm (Jun 28, 2018)

uncle eddie said:


> Here is the part they sent to me...
> 
> View attachment 368830



Well Eddie I think I have some unfortunate news for you.
What they gave you doesn't fix the problem, it would only cut off power to your smoker when it reaches too high of a temp.

I would imagine that your existing one is still working as well so this would not fix your problem.
They should have either sent a new controller (top plastic piece with buttons) or a new circuit board (goes in a panel and compartment in the bottom of the smoker).

Masterbuilt needs to send you the right parts.  If you want to do the simple rewire and go the PID controller route your problems would be solved.  I wish I had better news for you.  Let us know what you would like to do going forward and either way I'm sure the community can help you out :)


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## Bearcarver (Jun 29, 2018)

^^What Tall said.^^

I would try to get them to send you a new controller first.

If they won't then I would let Tallbm help you with the PID gizmo.
He has a good track-record on fixing guys up with that conversion.

Bear


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## uncle eddie (Jun 29, 2018)

They told me they wanted to try this first...then see what happens.  I agree that I thought the temperature woes were a controller issue.  But during my calls (2 of them), they put me on hold for a LONG time to consult and this is the way they wanted to go first...and since it was free, I went with the flow.


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## tallbm (Jun 29, 2018)

uncle eddie said:


> They told me they wanted to try this first...then see what happens.  I agree that I thought the temperature woes were a controller issue.  But during my calls (2 of them), they put me on hold for a LONG time to consult and this is the way they wanted to go first...and since it was free, I went with the flow.



Well if are going to replace the safety rollout limit switch with the one they sent you then be sure to use some Hi Temp spade connectors.  The connectors they use are trash and are like the 2nd major failure point of an MES lol.
These would do the job and are an exact fit for the MES:

While your at it you may as well use these hi temp ones and switch out the crappy connectors used at the heating element as well :)

Hahhaa you are like halfway through a rewire :D


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## PAS (Jun 29, 2018)

tallbm said:


> Well if are going to replace the safety rollout limit switch with the one they sent you then be sure to use some Hi Temp spade connectors.  The connectors they use are trash and are like the 2nd major failure point of an MES lol.
> These would do the job and are an exact fit for the MES:
> 
> While your at it you may as well use these hi temp ones and switch out the crappy connectors used at the heating element as well :)
> ...





tallbm said:


> Well if are going to replace the safety rollout limit switch with the one they sent you then be sure to use some Hi Temp spade connectors.  The connectors they use are trash and are like the 2nd major failure point of an MES lol.
> These would do the job and are an exact fit for the MES:
> 
> While your at it you may as well use these hi temp ones and switch out the crappy connectors used at the heating element as well :)
> ...


tallbm, for some reason your picture links dont show up on my Firefox browser.


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## tallbm (Jun 29, 2018)

PAS said:


> tallbm, for some reason your picture links dont show up on my Firefox browser.



Interesting, here is the address *https://tinyurl.com/y7px4ho6*


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## daveomak (Jul 3, 2018)

https://www.appliancefactoryparts.com/search/part/32683355/

The roll out switch is also available from the above....


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## uncle eddie (Jul 4, 2018)

The repair is complete...heating up the smoker now to see how it does.  If it does OK - ribs going on in 90 minutes.

I thought I would post the pictures for the repair as there were a few surprises.  Total repair time was about 30 minutes.  It would have been easier with 2 people, maybe save 5 minutes of repair time.

The before







Note the new bolts/nuts were much smaller than the old ones and they are all tiny.  They slipped right through the MES40 housing case.  I had to slightly drill out the holes on the new part using a 5/32" bit to make the old nuts/bolts work.

I also needed some penetrating oil to loosen the nuts, a pair of pliers and a standard sized Phillips screwdriver






I would venture to guess that MasterBuilt should spend a few more pennies on their connectors...maybe use high heat ones?  This could be from when my MES40 got hot (315F or so)...but since the smoker can be set at 275F, I would venture to guess these connectors are not rated for the heat.






I pulled the melted plastic off and decided the actual wires/clips were OK.  Since they are covered, I plan to leave it this way...unless it causes a problem.






All of the tools used.  The directions provided by MasterBuilt were actually spot-on.






I was skeptical if this repair would fix the temperature control issue, but it seems to have done just that.

I have been running the smoker at 250F for 40 minutes now...and:

It got to temp much faster than before the repair
The temperature controller appears to be working again
The temp is holding within 10 degrees (+/-) of 250F as checked with 2 separate calibrated thermometers - acceptable
I do not smell burning electronics :)
Time to fill the AMNPS and get the St. Louis Style pork ribs on...


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## uncle eddie (Jul 4, 2018)

Well that didn't last long.  Smoker temp spiked to 315F.  Doing the same temperature spikes again.

Calling Masterbuilt tomorrow


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## Bearcarver (Jul 4, 2018)

uncle eddie said:


> Well that didn't last long.  Smoker temp spiked to 315F.  Doing the same temperature spikes again.
> 
> Calling Masterbuilt tomorrow




Yup---I still think it's your controller.
I had the same thing with a new one---It even made the Insulation make Crinkling noises.
They sent me a new controller----10 minutes later No more problem. Works perfectly ever since!

Bear


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## tallbm (Jul 5, 2018)

uncle eddie said:


> Well that didn't last long.  Smoker temp spiked to 315F.  Doing the same temperature spikes again.
> 
> Calling Masterbuilt tomorrow



Yeah that make sense.
What they sent you was the safety cutoff switch not anything that is suppose to constantly regulate the temp.
Also you are right, they don't use hi temp connectors and after the controller the connectors on the switch you replaced and the heating element are usually the next things to go.  They just corrode away very easily.


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