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Thread: Help with Modine Hot Dawg PLEASE

  1. #1
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    Help with Modine Hot Dawg PLEASE

    I have a problem with my 45,000 BTU Hot Dawg heater, and I can't find anyone who can help. It is an older 102 model series

    PROBLEM: When the heater comes on initally, the exhaust fan runs for a couple of minutes. The burners light and burn well. A short time later, the circulating fan comes on. So far, so good. Now, the heater will burn for a while, maybe even come up to where the thermostat is set, and then the burners go out. But the circulating fan continues to run, and will not shut off. To get the heater to light again, I have to shut the electric off to the heater and let it sit for maybe 1/2-3/4 of an hour. When I turn the electric back on to the unit. It repeats the same cycle.

    WHAT I'VE DONE SO FAR: Called the service guy (because I don't know jack about this stuff). He checked the gas pressure before it lights and after it lights. All is good there. Replaced Terminal Board w/time delay relay (at Modine's suggestion). That didn't work. Contacted the factory sales rep. Was told that Modine is familiar with this problem and there is a problem with the wiring harness. They sent me one at no charge. Didn't work.

    There's not a lot to these things. Somebody ought to know what's wrong. About the only other things to change is the gas valve (at nearly $200), the pressure switch ($55) or possibly the high limit switch ($30). The Terminal board was $70.00. I can buy a new heater for just over $350.

    Has anyone else had a similar problem, or have any idea what the problem may be? I'm getting desperate here. I haven't been able to work in the wood shop all winter because I don't have any heat.

    Thanks for any help you can offer.

    Jim

  2. #2
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    I do not own nor have I operated a Modine heater. It sounds to me like you are getting an overtemperature cut out. Turning the unit off for a period of time would allow the unit to cool and reset the temperature cut out. Yours may be defective or the unit may actually be getting too hot. Based on the parts lists I looked at for various models it looks like it might be item #25 or #40. I would suggest running the unit until it cuts out and then check this switch with a continuity meter right after it cuts out to see if it is open or closed.
    Lee Schierer
    USNA '71
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  3. #3
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    Usually with over heating the combustion air motor shuts off and the circulating blower may keep running.

    Next time it does that disconnect the thermostat wires to it, if it doesn't shut off I might lean to wards the board.
    Shutting the power off usually resets the board, and that's where I'd put my guess at.

    Al
    Remember our vets, they need our help, just like they helped us.

  4. #4
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    A friend of mine who is an HVAC guy helped me when I had a problem. Turns out mine was a chunk of snarf in the burner but he said that the control on those is solid state and there isn't much beside replacing the board that can be done to them.

    It runs so it isn't gas flow or ignition. Overtemp will shut it down but the fan should shut off at some point. Have you checked the flashing lights when it starts malfunctioning? There is a code there that is supposed to help when there is a problem.

    Joe
    JC Custom WoodWorks

    For best results, try not to do anything stupid.

    "So this is how liberty dies...with thunderous applause." - Padmé Amidala "Star Wars III: The Revenge of the Sith"

  5. #5
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    Victor, New York
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    hot dog not sizzling

    Jim: If it is an old unit it might have a thermocouple. This is a small copper tube that goes from the gas value to the pilot light (if it has a piolet light). It is a safety device. It must sense heat at the pilot light or the gas valve won't open. I used to have to change those on gas boilers and sometimes gas water heaters. They are cheap and generate a few milllivolts of electricity that is sent back to the gas value to run that safety feature. If it is not the thermocouple ( if it has one ) then I would suspect the temperature overlimit switch which would also have a bulb of some kind to sense the heat and temperature. If you look at the schematic diagram for your heater you could find the devices that are capable of shutting your heater down. Also you could call Modine and ask them. They are a well known company and probably would help you.
    Good Luck,
    Gary

  6. #6
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    Joe:
    The code flashes bright/dim all the time. That indicates "normal operation".

    Gary: My heater does not have a pilot light. It has a hot surface igniter. I've called Modine several times. They are the ones that suggested the terminal board and the wiring harness. They are not real keen on talking to someone who is not a licensed contractor.

  7. #7
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    Unhappy Let me just add ....

    Jim is one of my best friends and he lives just a few miles from me. I have been jealous of his shop for many years. In fact, he is one of the reasons I finally built my own shop. Anyway, this little Modine Hot Dawg heater has been performing very VERY well for many years. This year all of a sudden it started causing him a problem.

    He has engaged just about every source for help one could think of. He has had a local service technician, who has worked on these units or similar ones for years stop by on several occasions and has never found what is the cause. He has contacted Modine (and they really weren't that much help) although they did put him in touch with a repair facility in a nearby city. This company has been helpful and has made several suggestions but, alas, none of them worked.

    Now, since Jim has told you about the symptoms, if anybody has a clue what to look for next please let us know. I know Jimmy is almost at wits end and since he is a recently retired Deputy Sheriff it goes without saying he isn't tripping over his excess folding money if you know what I mean. Won't be long and a new heater would have been the better choice.

    Brad

  8. #8
    If the exhaust fan is actually running for a couple minutes that seems too long. I would disassemble the exhaust section and make sure there are no obstructions in it. The symptoms sound just like an R.V. furnace that mud-daubers have gotten into and plugged the exhaust. They even sell special screens for the exhaust to keep them out.

  9. #9

    Check pressure switch

    I had the exact same problem with a Hot Dawg a couple years ago. I replaced several components with no success, then I found by accident that there was a piece of sawdust in the hose to the pressure switch (diaphram that monitors that the internal exhaust fan is running)

  10. #10
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    Check all the connections to all the sensors and re tighten the brackets that hold the sensors. also check the screws that hold the control board to the unit. If I remember right two of the screws are ground screws for the board. Dale
    Happy Sawdust
    Dale

  11. #11
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    """"""""""""
    PROBLEM: When the heater comes on initially, the exhaust fan runs for a couple of minutes. The burners light and burn well. A short time later, the circulating fan comes on. So far, so good. Now, the heater will burn for a while, maybe even come up to where the thermostat is set, and then the burners go out. But the circulating fan continues to run, and will not shut off. To get the heater to light again, I have to shut the electric off to the heater and let it sit for maybe 1/2-3/4 of an hour. When I turn the electric back on to the unit. It repeats the same cycle.
    """""""""""

    Couple of things here, check to see in the manual if there's a pre purge cycle, every time you shut the power off you may have to go though the start up, it may or may not be a different length of run time the normal cycling is.

    What controls the circulating fan?
    If there's a separate fan control it may be sticking, that's why it won't shut off (maybe)

    That would tend to wards at least two problems, Scott mentioned one of them in something in the pressure switch circuit being faulty, stuck switch, plugged lines, etc.
    That would be why your combustion air blower runs so long, its not making the switch up inside the pressure switch.
    Any basic service tech should be able to check that unless I'm missing something here (probably)
    Especially if it does it on a regular basis.

    The other problem sounds like the board is not reseting internally, and by shutting the power off it resets its self.

    If I had to shotgun this with a on line guess, I'd replace the pressure switch and hose that connects to it first.
    That would be the cheapest cure.

    Also does the ignition system use a spark to light the pilot or is it direct light and a spark lights the main burner, there may be a flame sensor in there and that probably is dirty.
    Checking the Modine site at least some of there models have flame sensors, and in a wood shop dust is gonna get on them and cause problems, check their site and see if your model has one.
    If cleaning that doesn't do it, I'd try a board.

    Hope this helps alittle.

    Al
    Remember our vets, they need our help, just like they helped us.

  12. #12
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    Nov 2006
    Location
    Columbus, Ohio
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    105
    Quote Originally Posted by Jim Sears View Post
    I have a problem with my 45,000 BTU Hot Dawg heater, and I can't find anyone who can help. It is an older 102 model series

    PROBLEM: When the heater comes on initally, the exhaust fan runs for a couple of minutes. The burners light and burn well. A short time later, the circulating fan comes on. So far, so good. Now, the heater will burn for a while, maybe even come up to where the thermostat is set, and then the burners go out. But the circulating fan continues to run, and will not shut off. To get the heater to light again, I have to shut the electric off to the heater and let it sit for maybe 1/2-3/4 of an hour. When I turn the electric back on to the unit. It repeats the same cycle.

    WHAT I'VE DONE SO FAR: Called the service guy (because I don't know jack about this stuff). He checked the gas pressure before it lights and after it lights. All is good there. Replaced Terminal Board w/time delay relay (at Modine's suggestion). That didn't work. Contacted the factory sales rep. Was told that Modine is familiar with this problem and there is a problem with the wiring harness. They sent me one at no charge. Didn't work.

    There's not a lot to these things. Somebody ought to know what's wrong. About the only other things to change is the gas valve (at nearly $200), the pressure switch ($55) or possibly the high limit switch ($30). The Terminal board was $70.00. I can buy a new heater for just over $350.

    Has anyone else had a similar problem, or have any idea what the problem may be? I'm getting desperate here. I haven't been able to work in the wood shop all winter because I don't have any heat.

    Thanks for any help you can offer.

    Jim
    Jim

    I had similar problems with my Hot Dawg heater a few years ago. I replaced the circuit board and that fixed the problems for a while and then another problem started, the exhaust fan wouldn't come on and the burner would not light but the air circulation fan would come on and not shut off. Since I had just replaced the circuit board I figured it was something else, and it was...............Bad thermostat contacts. I had used an old thermostat and the switch contacts were dirty and causing low voltage to the unit.

    I wired around the thermostat and things started to work again.

    You might try taking the thermostat out of the circuit and just shorting the wires together to see if the unit works correctly. The burner/fan circuits seem very sensitive to low voltage to me.

    Here's some pictures of my setup and the insides. It's the 30K btu unit.

    http://mrcol.freeyellow.com/hot-dawg/

    Hot Dawg service manuals and wiring diagrams.

    http://www1.modine.com/publications/...ine+Literature
    Last edited by Ron Coleman; 02-19-2008 at 11:04 PM.

  13. #13
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    Jan 2006
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    Hey Ron..Thanks for taking the time to post the pics and suggestions. I appreciate it. Everything on your heater looks like mine (duh, It's a Hot Dawg) except I have 3 burners instead of 2. Changing the thermostat was suggested to me by Brad. But I haven't done that yet. Might try it today.

    Al..My heater has a "hot surface" ignitor. There is no problem with the unit firing. It lights right up the first time. Problem is that the flame goes out before things come up to temperature and then the circulating fan runs all the time. Then it will not relight until I remove the power from it for a while. As far as what control the circulating fan, I assume that the terminal board does. EVERYTHING is wired through the board. As for the pre-purge cycle, I assumed that when the exhaust fan comes on first thing (before it lights), it is purging the system. Is that what you are talking about?

    Scott..I'll check the pressure valve and hose today when I check the thermostat. Thanks

  14. #14
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    """""""""
    Al..My heater has a "hot surface" ignitor. There is no problem with the unit firing. It lights right up the first time. Problem is that the flame goes out before things come up to temperature and then the circulating fan runs all the time. Then it will not relight until I remove the power from it for a while. As far as what control the circulating fan, I assume that the terminal board does. EVERYTHING is wired through the board. As for the pre-purge cycle, I assumed that when the exhaust fan comes on first thing (before it lights), it is purging the system. Is that what you are talking about?
    """"""""

    If it shuts off before temp we can have several probs, I couldn't find a parts list for a hot surface so I don't know if it has a flame senor or not, what happens is when the main burner comes on the module has to be told that there is flame, this is usually done with a sensor (prob looks like a 1/8th in thick rod that has its end in the flame and the other end has a wire going to the module....or...its done though the hot surface ignitor.

    Sensor/ignitor or module could be bad

    or..

    Thermostat is shutting down early due to faulty stat or the anticipator, if you turn the stat to 90 does it run longer before shutting down??

    or..

    Any of the other things that have been mentioned.

    Considering everything is controled though the board I'm still leaning that way
    Hard to be sure with out being there though.

    Al
    Remember our vets, they need our help, just like they helped us.

  15. #15
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    "If it shuts off before temp we can have several probs, I couldn't find a parts list for a hot surface so I don't know if it has a flame senor or not, what happens is when the main burner comes on the module has to be told that there is flame, this is usually done with a sensor (prob looks like a 1/8th in thick rod that has its end in the flame and the other end has a wire going to the module....or...its done though the hot surface ignitor.

    Sensor/ignitor or module could be bad"


    There is no prob in the flame. The only thing similar to that is the HL switch which is inside the cabinet where the heating tubes are located. But it does not touch the flame. So it must be built into the ignitor.

    Thermostat is shutting down early due to faulty stat or the anticipator, if you turn the stat to 90 does it run longer before shutting down??"
    "
    Seems to run a little longer if I turn the stat up higher. But still shuts down and circulating fan continues to run. I don't what the anticipator is or where it is located.

    P.S. Wish you were here

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