MM 360 Problem

I’m about at my wits end with one of my ovens. It’s a MM PS360. It was purchased reconditioned almost exactly three years ago. I have been having the same sporatic problem with it for the last 4 months and nothing seems to fix it.
When we turn it on, preset to 450, it heats and sounds fine. Sometimes it will hold the temperature for hours but usually just about 30-45 minutes and then it will drop, usually to around 350. Sometimes it will maintain this temp for just a couple of minutes then go back up but other times it will stay down longer. Alot of times after it does it once it won’t do it again, but not always. Its so sporadic no one can seem to diagnose it. In the past couple months I’ve put a laundry list of new parts on it
Control panel
Door switch
Fan motor
and several other small switches and wires inside.
I don’t have much experience with appliances but am pretty mechanically inclined and I’m stumped.
I’ve had a repair man come and look at it 4 times (same repair man) who can’t figure anything out either. I’ve searched my yellow pages and can’t find another repair man that will look at it ( actually had one tell me he wasn’t accepting new clients).
I’ve spent about $1400 on it in the past 4 months and still can’t depend on it. Anyone have any suggestions?

get a qualified oven technical in to look at it. It may cost more up front but I bet you’d have got the thing fixed by now and without all the part’s you guessed were wrong.

When you’ve found a good tech then get them to come in twice a year and give the oven a service. Its you key equipment item and needs to be running correctly!

Could it be something as simple as a gas regulator that is acting up?

I agree, get a proper technician and get it fixed right. Thos eparts and aggravation probably cost you more than if a tech was called out during the first realization of a problem.

One of our stores had a similar problem that they couldn’t seem to diagnose. After a couple years they finally figured out they were lacking the required gas pressure to their triplestack. Might be a good starting point for you.

Hi Bjack

The factory requires a dedicated gas line of 2- in for those ovens and 6 in of water column pressure at the oven.If other gas appliances are on the same line they could starve the oven.

If that is not the problem It is most probably the temperature control unit or the high limit switch.

If not those items It could be a bad wire some where or ??

George Mills

We had a recent situation where the oven (MMPS360) would get to temp and then when the temp dropped the igniter wouldn’t switch back on and the temp kept going down. We would notice the lack of noise when the booster didn’t kick back in. You would hear the click, click of the ignited just like a switch that had sticking points. It didn’t happen all the time, just spaoradictly.

My repair guy replaced the igniter and it has ben fine ever since. Cost $600 all up including checking other likely causes, and this is AU$ where our parts and labour costs are far greater than the US.

It sounds a very similar situation so this may be worth checking out.


This may be out there, but don’t they have a sensor that detects when a pizza is run through? When it doesn’t see one it powers down 50%, then when it sees one it powers back up? Did I read an ad wrong or may it be a valid solution to check? 2 cents inserted.


I think you may have read about the new WOW oven by MM which does that, or some other oven :?

As the MMPS360 came off the ark with Noah and the animals I don’t think they had thought of that then.


That’s exactly what mine is doing but I’ve already replaced the ignitor.
I also wouldn’t think it was the pressure because it has worked perfectly for 3 years and just started acting up.
Thanks for all the replies!

My bet’s on the high limit switch.

Also, when was the last time the oven was throroughly cleaned?

I’m having the exact same issue with same type of oven. Just started a couple months ago. Wondering if it has anything to do with when the gas furnace comes on. Any luck with your issue bjack?

I had this exact same problem once - my really good repair guy couldn’t figure it out and went on a part swapping frenzy over time - never fixing it.

I finally figured it out - the “spark plug wire” that goes from the ignition box to the ignitor was the problem - check the connection to the ignition box - it is probable very loose - but making contact. Pull it off and take a look at the connector on the end of the wire - mine was full of carbon, I assumed from arcing - because it didn’t have a good connection to the box.

Get a can of electrical contact cleaner at Radio Shack or Home Depot. Clean the connector with that, and with a pair of needle nose pliers, squeeze the connector “closed” a little bit so that when you slide it back onto the ignition box it will be a firm fit.

This may or may not be your problem - but I never had the “stop heating” issue after I fixed this.