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  • Hobart C44AW dishwasher issue

     nafets47 updated 1 month ago 6 Members · 36 Posts
  • nafets47

    Member
    February 25, 2020 at 11:26 am

    So when my dishwasher is moving the trays through the machine there is a intermittent noise sound, not a grinding noise and not a squeak. Sort of like moving a chair on a waxed floor.

    I looked under the washer while it was running and saw an ever so slight movement of the conveyor motor. Is it likely that this moving is rubbing and making the noise? Also any clue what would be the fix?

    Looked through the manuals and this was not covered.

  • nafets47

    Member
    February 25, 2020 at 11:49 am

    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 - ADK NY

    Member
    February 25, 2020 at 1:23 pm

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

  • nafets47

    Member
    February 25, 2020 at 3:55 pm

    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 - ADK NY

      Member
      February 25, 2020 at 4:14 pm

      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

        Member
        February 25, 2020 at 4:59 pm

        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

          Member
          February 25, 2020 at 5:01 pm

          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

            Member
            February 25, 2020 at 5:40 pm

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

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

        • ectofix

          Member
          February 25, 2020 at 5:52 pm

          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

            Member
            February 25, 2020 at 6:42 pm

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

            • ectofix

              Member
              February 25, 2020 at 7:39 pm

              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

                Member
                February 27, 2020 at 12:46 pm

                That part number changes.

                Item ID: 00-815724

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

  • fixbear - ADK NY

    Member
    February 26, 2020 at 7:04 am

    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

    Member
    February 26, 2020 at 8:52 am

    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 - ADK NY

    Member
    February 26, 2020 at 10:02 am

    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

    Member
    February 26, 2020 at 11:16 am

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

  • nafets47

    Member
    February 27, 2020 at 1:34 pm

    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

    Member
    February 29, 2020 at 8:58 pm

    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 - ADK NY

    Member
    March 1, 2020 at 11:33 am

    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

  • olivero

    Member
    March 1, 2020 at 11:45 am

    I don’t quite see how RTV sealant or any type of insulator could reach a higher temp than what it’s submerged in.

    Delayed ignition or “barking” would be caused by either too much of either air or fuel or not enough of either OR the igniter not sparking enough or heating up enough (depending on the style) and so the chamber has time to build up gas and create a “bark”.

    Fixbear,

    Having already replaced the high limit, with a gas burner below, the only reason I could imagine is that somehow the cap tube from the high limit is getting hit by the flame or the exhaust of the burners, there’s simply no way it’s being caused by the water, UNLESS there is an intremittent thermostat fault that allows it to go higher at certain times, but from what I understood, Nafets has been there, probe in hand measuring the temp and seen it to match the installed temp gauge and then have the hi limit trip, so that to me; indicates some other sort of heat source getting at that cap tube.

    What’s your take on that? I haven’t worked on any gas dishwashers before so I don’t know enough about them to say where and how but just theoretically.

  • nafets47

    Member
    March 1, 2020 at 4:15 pm

    Yes. Like olivero was stating, the temp on the gauge is the exact temp in the wash tank. Just so it is understood, the high limit that is tripping is from the wash tank not the booster.

    Since I am not in front of the dishwasher all day long and what was communicated to me by the person who is, is that the washer does not go past the 160* temp that cuts off the heat. I also verified that the setting of the electronics on top of the unit only requests temp to 160 then shuts off the ignitor.

    What I was thinking might be occurring, is that the gas air mixture is not correct (which is evident by the “barking”) and this sudden surge of heat is coming into the ignition box when it “catches” and is hitting the small amount of tubing that is exposed on the high limit (the remainder is in the immersion tube in the wash tank). Since I also found evidence of some burn residue on the new high limit I just installed. Does this seem accurate?

  • fixbear - ADK NY

    Member
    March 1, 2020 at 6:30 pm

    I don’t quite see how RTV sealant or any type of insulator could reach a higher temp than what it’s submerged in.

    When there is any form of insulation on a sensor it delays the reading. Yes, eventually it will reach the liquid temp, but heat saturation of the heat exchanger will make it rise higher than design. It will also call for heat later and you will see larger drifts in the temp than normal.

    so that to me; indicates some other sort of heat source getting at that cap tube.

    What’s your take on that?

    Does the cap tube slide into a tube fastened to the heat ex changer? Look for minerals between them acting as a heat sink

    UNLESS there is an intremittent thermostat fault that allows it to go higher at certain times

    That’s exactly what I was saying. But the question of does it have a rinse booster or not has not been answered. You may be looking at the wrong limit.

  • fixbear - ADK NY

    Member
    March 1, 2020 at 6:38 pm

    For sanitation purposes the rinse is normally 180F Hobart calls 160 wash as a min.

    Since I also found evidence of some burn residue on the new high limit I just installed. Does this seem accurate?

    Ouch. That means your new burner gasket is leaking. And depending on how much is exposed, yes.

  • olivero

    Member
    March 1, 2020 at 8:21 pm

    Fixbear, I still don’t believe it could rise that much, we’re talking latent heat upwards of 40*F, I’ve never seen that, especially not on an insulator.

    I think the flame or burn marks on the high limit cap tube is the main give away at this point, the so called “smoking gun” that’s what I would be thinking.

    It’s the wash tank high limit that’s tripping, the booster is just for sanitizing, it was mentioned in an earlier post by Nafets.

    • fixbear - ADK NY

      Member
      March 2, 2020 at 7:18 am

      That all depends on how clean the heat exchanger is. I’ve seen some with a lot of mineral buildup from a lack of de-limning..

      • olivero

        Member
        March 2, 2020 at 11:41 am

        I could see the HE insulating the heat but for it to transfer is what I have a hard time believing. I could see the source of the heat overheating but this is for the water, so that latent heat would have to transfer through the HE and into the water, latent which is what I’ve never seen, personally. I’m not saying it’s impossible, just that I’ve never seen it.

        • fixbear - ADK NY

          Member
          March 2, 2020 at 4:26 pm

          Olivero, It has to do with time and K value. If there is a material between the sensor and the water that has a high K value the time for the heat to cross to the sensor will be longer than the time of a low K barier. This means that the sensor will be late cutting off the heat call and overrun will happen. Bad enough that Hobart uses a large sensor casing to make it strong, and it already has a mass inside if that stainless probe that slows the sensing. Add anything else and the temp width will increase even more.. The actual thermocouple is embedded in a compound to transmit the heat. But even that has a K value. But very low. Like a heat sink compound.

          • olivero

            Member
            March 2, 2020 at 5:53 pm

            That I can understand, I thought the hi limit being covered in an insulator is what we discussed. I can understand the thermostat being insulated and then not reading the temp has passed it’s setpoint and then tripping the hi limit, that I believe and I have seen that.

            • fixbear - ADK NY

              Member
              March 3, 2020 at 12:14 pm

              The same thing can happen with a cap tube sensing that has been pinched or kinked. It can still function, but very slowly both open and closed.

              • olivero

                Member
                March 3, 2020 at 1:54 pm

                Yes, that makes sense. I think there was a confusion on my end in terms of what was being discussed.

  • nafets47

    Member
    March 2, 2020 at 11:17 am

    The water coming into the washer is 0 hardness if that means anything. The entire building has the water softened to 0 before it enters the pipes.

    Also another piece of data, and something that I am going to address as soon as my tool is returned to me, is that the high limit was reset last night and then the washer told me that it started “barking” and then wouldn’t get to temp. I check this morning and it was again tripped.

    So this I believe is now the issue to resolve. I will have that point fixed this afternoon and let everyone know tomorrow or tonight depending what is the result.

    • fixbear - ADK NY

      Member
      March 2, 2020 at 4:32 pm

      “0” ? what is it, distilled or RO. Your machine need at least a 6 for longevity.Have you chemical supplier test it to be sure. That’s pertly low and will cause heat exchanger problems.

  • nafets47

    Member
    March 2, 2020 at 5:42 pm

    We have a water softener system which uses salt. The chemical provider worked out the appropriate chemical for our system and has been working well.

    We have a water treatment company come out once a month to check chemicals for my chiller loop on the property and it is always 0 water hardness. Believe it or not this washer has been running for 13 years for two work shifts every day. Pretty crazy.

    Anyway, using a manometer the gas was checked and was 3.4 not 3.2 like it should be. The washer was barking every time I fired it up checking the gas until it hit 3.2. Now no noise and fires up on the first try. So we shall see.

  • nafets47

    Member
    March 4, 2020 at 10:52 am

    An occasional “bark” afterwards. Took apart the blower fan and found some loose paint inhibiting the blower from moving freely. Cleaned that up, removed any and all barking and no longer tripping high limit.

    So looks like this one is a DONE.

    • fixbear - ADK NY

      Member
      March 6, 2020 at 1:33 pm

      I suspected that you had something restricting the air. Glad you got it.

  • nafets47

    Member
    March 6, 2020 at 4:54 pm

    Yea, I did too originally. I spun the blower by hand and didn’t hear or feel anything inhibiting movement. Only after taking it apart did I find loose paint.

    Thanks, me too and so is the guy who washes dishes.

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