MM Oven problem

So this morning during a $800 hour, my top oven decided to stop cooking pizza’s on the bottom of the pizza only. The top of the pizza’s were still cooking correctly, but we had to throw out about 5 pizza’s because the bottom of the pizza had not finished cooking and was still soggy, we couldn’t even cut the pizza off the screen.

This oven has had issues for several years now, we usually just have to rotate the pizza half way then push it back a bit to get a proper browning on the whole pizza. I also noticed that the temp on the display was ranging lower then normal (i.e. it was getting to 10+ degrees below my set temp and fluctuating wildly above and below it).

About a year ago i asked my oven guy to look at the oven while he was fixing the bottom one, and he said everything was fine. I still suspect the gas valve is going bad, and i had read on other posts that there is a optical sensor inside the oven that controls it ?

Anyone have any idea’s on what could be causing this ?

sounds like you lost a main blower motor, or it over heated causing it to shut down (which can be caused by the little axil cooling motor going out) or it messed up and started running backwards. I have all these exact issues happen to me over the last 5 years. If your able to do some self testing, test the fuses behind the temp control door and see if you lost a time delay fuse. This happned to me last week actually, threw a new fuse in and good to go

MM360s have 2 blowers, one for the top fingers 1 for the bottom fingers, so a double stack would have 4 total motors.

Thanks for the info, i will take a look tomorrow before we open.

No problem, I know the middleby marshal ps360 like the back of my hand, if you have any questions feel. Free to ask

Joker -

How do you think a Middleby ps360 stacks up against Lincoln Air Impingement Ovens?

I’ve used a MM for years, but need to upgrade from a single to a double. I found a great deal on a double, but it’s a Lincoln, which concerns me.


You couldn’t give me a lincoln oven, i am just not a fan of them at all, i started with a lincoln and now with MM. My major problem with them was that they were to small, and the capacitors and blower motors seem to go out more them MM

Joker knows MM ovens.

I can only think of one other probability. If you run any product through wrapped in foil it is possible some of the foil was sucked into the blower system and is blocking the air flow.

George Mills

We do use foil for the hot wings, but very very very rarely will a sheet go in full and not come out full. When that happens it usually gets baked into a pizza :mad:. Didn’t have a chance to check the oven this morning, Revention caused a database error and i spent the morning on the phone with them to get it fixed… Will check tomorrow morning

@George Mills

Good call on the foil. I forgot about that one. It’s happened to me as well, however it Seems to happen over time not all at once.

When it happened to me it was gradual and I ended up with about 10 foil sheets blocking the wheels and it was in both of them, not just one. Couldn’t figure out why I had to crank the heat up all the time lol

@d9phoenix any luck on your issue?

Just got done inspecting the oven, Cleaned out the exhaust fan vents on both sides, the fuses all look good. I do not have a tester with me. From what you describe could be the problem and what happened i am thinking it overheated.

I kept cooking buffet pies in that oven, but we stopped cooking anything with more then 1 topping that day in the oven. Going to use it solo today and see what happens. Have to dig out my testing equipment and see if i even have a fuse tester, or if my DMM still works. If they all test out good i will take apart the bottom fingers and check for foil before i call my oven guy.

If it over heated, it should be back to working normal by now. The main blowers have a thermal overload inside them so if they get hot they shut down until below a certain temperature. So regardless if you lost a little cooling fan, after an hour or so it will work again until it gets to hot and shuts down

As for the fuses, they will look just fine even if they are good or bad, you need a volt meter to test the continuity and make sure they are all good

Check that 1st, as i highly doubt you have foil in the fans, and if you do you need to pretty much dismantle the entire upper oven, upper fingers, lower fingers and conveyor belt, as its next to impossible to see up top where the blowers are located. The foil would not be in the fingers themselves ( or at least highly unlikely) the foil gets sucked up into the squirl cage blower wheels located in the middle of the oven above the top fingers, there are 2 of them they look at each other.

Hope this helps before you have to call the 100 dollar an hour oven guy


What model MM oven to you have? I think everyone is assuming 360’s, but you mentioned “optical” in your first post, and there isn’t anything optical in a 360.

If it is a 360, and the blower motor was stopping, you would see the heat drop as if you had turned the heat switch off. There is a centrifugal switch on each blower motor that is part of the heat circuit. It must be closed (by the motor spinning) for the heat circuit to have power.

I am not entirely sure what exact model it is, but it has a 32" wide belt and the conveyor is 84" long. It is just like every other MM oven i have worked with just smaller (i worked with the 360WB for years). The picture jokergem just posted is almost identical to what the oven looks like inside (yes i have completely dismantled it and moved it and put it back together under the previous owner as i was the GM at the time).

The oven has been running all day so far with no problems, so it looks like it is a overheating problem.

As far as the optical thing, that was just something i had read in previous posts about oven problems and how it maintained the temp. I did not know if it used one or not. I have not had time to go thru the manual or spend time with the oven guy the two times he has been in to fix it.

I would think there is a ID plate on the oven somewhere that says the exact model and serial # ?

Its under the glass window door. At a hard angle pointing at the ground

Really stupid location if you ask me

You have to kneel down and look up at the frame of the window deal

And that would be why i have never seen it lol. I clean it all the time but never look at it. Will let you know tomorrow when i get in

Well the plate was missing from the bottom oven, but the top oven still had it. Barely readable, but yes it is a PS360.

If this is happening, it is almost certainly a faulty temperature controller. Can you post a picture of it?

More likely then a temp controller it would be a therocoupler, in the back of the oven, sending false reading for the temp controller to display. ( I totally missed your quote about the wild fluctuation in your 1st post)

Possible, I’ve just never seen a thermocouple have an intermittent issue. I’ve had more than a few temp controllers flake out once they heat up a bit. Sometimes opening them up and hitting some of the through-hole components with an iron resolves problems with bad solder joints, sometimes they just need replaced.

It would be pretty easy to isolate by just switching the temp controllers between the top and the bottom oven and seeing if the problem moves or if it stays.

Each oven has a different controller, i honestly do not know which one is the original (if any)
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