why does my Hobart AM15 dishwasher keeps steaming when cycle is complete?

[fixbear]

Check your booster controls and heat relay.  The rinse is directly out of the booster.  It will have a primary control and a safety.   The tank temp and tank heater has nothing to do with it.  As for fill valve, are you referring to the solenoid valve for water or the anti syphon valve on top.  If the booster goes over 212F at sea level it will continue to push water out the rinse arms from the water in it boiling..  

[ectofix]

Along with what fixbear said, I’d be taking a closer look at that fill valve again.  I’ve never had much luck with just cleaning a solenoid valve.  I’d go ahead and rebuild it.

 

If your dish machine’s serial no. is before 231154994, a valve rebuild kit part number is 00-893101.  When bought from Hobart (or PartsTOWN), it costs roughly 60% of the price of a new solenoid valve. If your dish machine’s serial no. is 231154994 or after, a rebuild kit isn’t listed in their parts manual.

 

Here is Hobart’s latest & greatest parts manual:  AM15 SERIES DISHWASHERS – CATALOG OF REPLACEMENT PARTS

 

In either case, I’ve no doubt that they’re both Parker valves.    As such, you have the option of taking accurate data from the valve to check with your local Parker distributor in order to get a rebuild kit.  Probably cheaper that way.

[guest]

In addition to the above, I would look at changing the hi limit on the rinse tank. it is located on the front of the tank and has a manual reset button. It may no longer be operating properly. This has nothing to do with the heater running too hot but should stop the heater from working when it gets too hot. If you are not using soft water for your machine, I would ask your tech about descaling the boiler. This too can cause the rinse to run too hot.

Final rinse should run about 185deg. Two hundred is a little high and, stream coming out of the spray arms would make it seem that it is even higher. Have a qualified tech look this machine over.  

[guest]

I was referring to the solenoid valve for water.  It stopped spraying after I cleaned it. It may not have shut off completely but it helped.  I will rebuild the valve but it seems like the control board is the only thing limiting the booster temp as far as I can see. I’ve unhooked the resettable high limits which disabled the booster and running chemical sanitizer at the moment.  

[fixbear]

He did not say that the high limit has been tripping.  So why would one replace it?  As for mineral build-up in the booster, Good point. If loaded like some I’ve seen,  it would hold enough heat to keep heating the water after a call for heat long enough to boil the water but not trip the limit. As it is below the heaters and in a area that will always stay wet..  Even though the temp probe is fairly high in the booster, minerals will insulate it.  Wish I had taken pictures of some of them I have come across.  Full to the point one had to pry out the heaters and chisel the build up loose. 

[fixbear]

genemattice,  We are in a bit of a fog here without the ML number.  I don’t know what options you have like a condenser or gas or drain tempering,  or even which booster.  Because the thermister is on a extension cable.  Make sure to ohm it at the control board first,  then at the booster.  They should be the same,  but cable failure is a possibility.  If you do it the other way you may have scraped the plug terminals enough that it will not show you the resistance as operating.

[fixbear]

That will not clean the booster.  The booster is fresh water that is added at the rinse phase.  I really recommend getting a new booster gasket and removing the heat bundle.  You’ll find a bunch of mineral buildup in the booster and a wet vac helps a lot with cleaning it.   Also a good flashlight and a long screwdriver.  Having fun on the floor.

[guest]

the ML # is 130039  with 3 phase 480 electric booster under the dishwasher.  I just chased the sensor wire out of tank and back   to control board and resistance was  the same.  Both kept climbing slowly while I was testing.  Maybe  the small current flow was causing heat.  Something that I failed to mention is that the booster tank was changed about a year ago due to a pinhole in it.  Now I’ve noticed that this tank is leaking also.  well, not exactly leaking yet but there are signs of the tiniest pinhole where limescale and almost undetectable moisture is present .  The more I look the worse it gets. 

[guest]

The unit is around 6 years old and the booster tank was changed last year due to a pinhole.  The Hobart Tech said he had never seen a stainless steel boster tank fail since he has worked on them (10 yrs).  I see now that the tank seems to have an almost undetectable leak in it.  If it weren’t for lime build up you wouldn’t see it.  I had changed that rinse thermister arund a week before all this started and it worked fine for a week.  The rinse temp has always been a little higher than normal as far as I know and the incoming water temp is not much over 110. 

[fixbear]

That sounds like you have either a electrolysis problem or a water problem.  Did Hobart replace it or someone else?  Ohm out the thermister to ground to make sure there is no leakage.  It should not climb.