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

[uncle eddie]

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.

 

[tag0401]

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

 

[mosparky]

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.

 

[uncle eddie]

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.

 

[mosparky]

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.

 

[uncle eddie]

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.

 

[daveomak]

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....

 

[daveomak]

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

 

[dr k]

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.

 

[Bearcarver]

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

Bear

 

[uncle eddie]

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.

 

[Bearcarver]

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

 

[uncle eddie]

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.

 

[Bearcarver]

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

 

[biteme7951]

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.

 

[uncle eddie]

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.

 

[daveomak]

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

 

[uncle eddie]

still waiting on parts....

 

[uncle eddie]

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.

 

[Bearcarver]

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