Hobart C44AW dishwasher issue

[nafets47]

I took another look and there is a bracket that has two bolts holding a piece of metal that is touching the conveyor motor wheel.

This seems like the cause of the noise, what would that be for?

[fixbear]

Then why is it touching? Did it get bent or mounted wrong.Or is the wheel in the wrong place?

[nafets47]

There was some calcium or some white hard powder on the piece of metal.

But, I was looking at the diagram of the machine on PartsTown and this specific piece isn’t on the parts list or diagram. I moved the piece causing it to touch the wheel and the sound stopped.

[fixbear]

So solved or do you feel uncomfortable with it? Most of this type of work requires us to observe and look at what is really happening, not what they tell us.

[nafets47]

Damn it. I responded twice and it has not shown up.

The things that puts me off is why was it there in the first place, it seems out of place.

The motor is mounted to a bracket, so why is there (what appears to me) to be a random piece of metal which can slide and make contact with the wheel of the conveyor motor. The only thing I can think with is that it inhibits the motor for moving while pushing heavier items through the washer, but even then it seems like an added inapplicable part which you cannot find on the parts list or any diagram.

Furthermore I got a copy of the service manual from Hobart which surprise surprise is not very helpful when it comes to servicing the machine.

You would imagine the service manual would include a large trouble shooting section with what to do to fix XYZ, instead it says how to change out parts which I could figure out by looking at it. Sure there is some things like, what ohms should the thermostat be reading at certain temps. But overall kinda useless and the actual manual is equally useless.

Just today, I was running into the machine having the high limit trip two days in a row. Why is that happening? I adjusted the booster heater so it only goes up to 185* so it should not trip and seeing how the washer can only get to 160* before it turns off the burner why would the high limit trip when it is rated to 212*?

Anyway, this washer is a bit of a learning curve seeing how I previously have never worked on dishwashers or anything having to do with gas. Now I have electricity, gas, and water mixed into a small cabinet that was not properly maintained or service by the previous guy. So I am running into some catch up amongst many other machines things.

…. rant over.

So, what I communicated earlier is what I observed after the Dishwasher alerted me to the noise. Now after I personally ran it and put a few trays through the machine I confirmed there was no further noise.

[nafets47]

Do you mind shedding some light on what I was mentioning about the high limit tripping.

Kinda feel confused on this one. It is a brand new high limit. Sure it could be bad, but how would you know?

[ectofix]

You said that was the booster tripping the hi-limit?

Is the booster a separate unit, maybe made by Hatco or Lochinvar?

[ectofix]

REGARDING THE CONVEYOR MOTOR:

Without looking at a parts manual for the setup, my memory thinks that earlier C-Line A machines had the conveyor motor mounted onto a movable platform and held in position by spring tension. If the conveyor jammed for some reason and overcame that spring’s tension, the conveyor motor’s mount platform would shift and trigger a microswitch to disable the conveyor contactor. This, of course, was designed to prevent damage to the machine.

Later models C Line A machines (before that line was discontinued) incorporate a new circuit board mounted vertically on the back wall of the control box. The conveyor motor’s drive hub had radially-mounted magnets which passed in close proximity to a component looking like a Reed switch, but is actually a hall effect sensor. So, sort of a crude pulse generator tied into that new circuit board. As such, if the speed of the motor slowed for some reason, that circuit board would disable the conveyor motor contactor. So…an electronic version of a jam safety circuit.

[coolertapt]

I’d say a holifax sensor in a dish pit is about the wors thing I’ve ever heard of.

[ectofix]

All of OUR Hobart CLe machines use them. A hall effect sensor…that is.

I work in-house and we have four of those machines. The oldest has been running for eight years without a single problem with conveyor control.

NOTE: So NOW you made me look. That part (Sensor – Latching Hall) is out of stock at Hobart SmartParts and is listed as OBSOLETE by PartsTown.

That’s weird, because that VERY SAME PART is used in their CURRENT production CLeN conveyor dishmachines (which we ALSO have) – per a manual I found on Hobart’s Resource Center.

SO…it must be pretty dependable since (I’m assuming) there’s been no demand for replacing them.

I SURE hope I don’t, all of a sudden, need one TOMORROW.

[mr340]

That part number changes.

Item ID: 00-815724

Description: KIT, SENSOR, LATCHING HALL C/W BRACKETS, SERVICE

[fixbear]

The motor is mounted to a bracket, so why is there (what appears to me) to be a random piece of metal which can slide and make contact with the wheel of the conveyor motor. The only thing I can think with is that it inhibits the motor for moving while pushing heavier items through the washer, but even then it seems like an added inapplicable part which you cannot find on the parts list or any diagram.

Manufacturers never add items that are unnecessary. Sometime in testing they found something they thought they needed to change. This cost money and time. Making their machine less cost effective. It may just be a slash protector for a seal or something, but it has a purpose.

Now the overrun on temp, Check the actual temp with a calibrated and trusted thermometer. Also since you have a gas heated unit, scale can hold heat and cause rise after heat saturation. I don’t know your elevation, but 180 degree sanitation temp is very close to boiling. I believe that with gas heat your high limit has a capillary tube to sense temp. Is the tube near any other source of heat than the water? Perhaps a combustion leak or burner heat. It also can not have any kinks.

[nafets47]

So last night I found some liquid gasket material (same stuff that comes out a squirt tube) on the temp probe. The Dishwasher was instructed to clean it off and this morning no issue and no issue last night.

I guess it is possible that material was getting hotter than the water and activating the high limit.

Regarding that piece of metal I was talking about earlier, there were no wires connected to it. I will contact Hobart today or tomorrow to find out exactly what it is. However I only moved it a 1/16th of an inch so it isn’t making direct contact anymore.

And to answer ectofix’s question earlier, the high limit being tripped was in the wash chamber of the dishwasher not the booster.

[fixbear]

So last night I found some liquid gasket material on the temp probe

That would have a effect. The RTV sealant would act as a insulator delaying the probe from sensing the water temp

[nafets47]

Perfect. Happy to hear that was an accurate point to address.

[nafets47]

So the limit tripped again, then again, etc.

So, I went into the ignition box, found some wires which were corroded in the wire nuts from when I had a leak occurring.

Resolved this issue. However kept tripping.

I then opened the top and adjusted the set point for the dishwasher as the wash tank was getting to 170*-172* and the washer is only supposed to get to 160*

After some fiddling with the position, got it so it stayed at 160* on the money and low and behold has not tripped after refilling the washer approx 10X, putting a hose into the washer to keep the temp going down and continually firing the ignitor. I made the ignitor fire approx 50X and not a single high limit trip. And now if the washer gets to 158* ignitor fires and at 160* turns off.

Problem solved.

[nafets47]

So issue came back, but different. The high limit is still however tripping.

One thing that was just reported to me was that the machine occasionally “barks”, from what I understand that is due to low gas pressure building up then igniting causing a booming noise. I am going to check the gas pressure in the afternoon to ensure that it is at 3.2 like it is supposed to be.

Is it possible that this booming is causing a temporary spike in temp and causing the high limit to trip?

Also perhaps the temp float probe is bad, how would one test it? This point may be a misdirection, however at this point I do not know what to rule out.

[fixbear]

First off, have you actually measured at what temp the limit trips at. You are talking about the wash tank heater, right? Or do you have a boaster heater on the top for the rinse?

You may have a situation with the float switch temp probe wiring that is fluctuating from a bad connection. That’s what senses the temp and sends the call from the top controller down to the flame controller.

Now the volatile ignition is a whole different problem. Comes down to fuel air mix and spark. Check the blower restrictor plate to be clean. Motor to speed and exhaust clear. Manifold pressure. Anything that would change the fuel mix. As I recall you had a problem with water in the heat exchanger at one point. The old style did have crack problems before they added the extra brace