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Hobart AM 15
I’m struggling with this door type Dishmachine on and off for awhile now.heres the issue: rinse temp is low.found that the contactor for booster heater is not getting voltage.coil voltage for booster contactor,one side is jumpered from another contactor that is closing,the other side goes thru both safeties on the booster.i tested them,they are not open.i jumped them out ,still no power to the contactor.what info I could find for this Hobart is this test: short the j9 on the board and the contactor should close,which it does and pulls amperage equal on each heater leg.this leads me to believe the board might be the issue,but I don’t want to guess,I need to know and verify.the schematic does not seem complicated,what am I missing here?i checked the ohm resistance of probe in booster and it was right on for the water temp. Any ideas? Thanks
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14 Replies
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FWIW: Here’s a copy of that schematic for anyone else wanting to chime in:
what info I could find for this Hobart is this test: short the j9 on the board and the contactor should close,which it does and pulls amperage equal on each heater leg.
I’m no Hobart tech, but I vaguely remember one of our guys performing a similar test by using a set of those jumper pins. It appears that by jumpering J9, you’re triggering the “gate turn-off thyristor” (GTO) Q3 to conduct– which is the function usually performed by the circuitry of the control board when calling for booster heat. So…your doing that test tells us that Q3 is good.
i checked the ohm resistance of probe in booster and it was right on for the water temp.
What was your resistance value and at what water temperature?
Just from my own testing, I’ve determined that the thermistor should read around 90kΩ @77°F, 20kΩ @150°F and 13kΩ @165°F (didn’t do this test at booster temp of 180°+. Those are approximate values.
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I believe water temp was approx 150-160, resistance was 34k ohms
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Guest wrote:
I believe water temp was approx 150-160, resistance was 34k ohms
Well now. That don’t sound right.
My basis is from the notion that Hobart uses some semblance of what’s referred to as a “100k Thermistor”.
Here’s a resistance chart for one that I found on the internet. It cross-references relatively close to the numbers I gave you, give or take some:
Take note that this is just a general reference and that you should always consult the equipment manufacturer’s chart when available.
SO…from that chart, the probe’s resistance crosses to about 122°F – NOT 150 to 160°F.
Is that 150 to 160°F what you read on the display while the machine was in RINSE mode?
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Sorry,the wash temp was 150-160, but rinse temp was 115-120. I’m trying to post the booster heater test from Hobart manual here.
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Rocco Ferranto
Service Technician
Smart Care Equipment Solutions
T 800 822 2303 E rocco.ferranto@ecolab.com<mailto:rocco.ferranto@ecolab.com>
386 Wabasha Street North | St. Paul, MN<x-apple-data-detectors://2/1>
E ServiceRequests@Ecolab.com<mailto:ServiceRequests@Ecolab.com>
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…and which probe did you take the resistance reading from?
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My old company for fourteen years.
The most direct method to upload a PDF is to use the pull down menu up to the right of this screen. I don’t know well that works when using a tablet.
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The booster probe
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From everything you told me, it sounds like the control board. Sorry…
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Exactly where did you test the booster sensor? At the sensor or at the board/? The extension cable/connectors may be the problem.
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