Help with Modine Hot Dawg PLEASE

[Jim Sears]

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

[Lee Schierer]

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.

[Al Willits]

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

[Joe Chritz]

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

["Gary Brewer"]

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

[Jim Sears]

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.

[Brad Noble]

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. :mad: :( :eek:

Brad

[gary rogers]

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.

[Scott Houghton]

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)

[Dale Lesak]

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

[Al Willits]

""""""""""""
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

[Ron Coleman]

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/litnav.php?c1=CHVAC%26R&c2=Modine+Hot+Dawg&c3=Contractor+Information&c4=Online+Literature

[Jim Sears]

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:D) 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

[Al Willits]

"""""""""
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

[Jim Sears]

"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:D

[Al Willits]

Anticipator is in the thermostat, it shuts the furnace down early so the temps don't overshoot.

Flame may be ok but if the sensor (whatever it is) isn't ok, it may not tell the module all's well.

Ya, being there would make it easier..

Al

[Jim Sears]

Thanks Al..Will check it

[Brad Noble]

OK Sears, give it up. What did you find out so far? Have you tried to bypass the thermostat yet?

Hurry up Jimmy, I got a couple of music box jewelry boxes I need to get built and you're holding me up! :D :D :D :D

BTW, ain't it great - the amount of help you get over here on the creek? Like I said, good people on the creek.

Brad

[Jim Sears]

OK Sears, give it up. What did you find out so far? Have you tried to bypass the thermostat yet?

Hurry up Jimmy, I got a couple of music box jewelry boxes I need to get built and you're holding me up! :D :D :D :D

BTW, ain't it great - the amount of help you get over here on the creek? Like I said, good people on the creek.

Brad

Give it up? That's exactly what I'm going to do. I just came back into the house from the shop. I took the pressure valve and hose off and cleaned them. Tried it again. SOS. I bypassed the thermostat. Ditto. I've had it. If the service guy and Modine can't figure something out, it looks like I'm going to be a warm weather woodworker. And you are absolutly right. These guys have been great. Thanks guys

[Al Willits]

OK, lets try and get this in as simple a form as possible.
List all the things that could be wrong
List all the things you have replaced
List what's left

Al

[Brad Noble]

Give it up? That's exactly what I'm going to do. I just came back into the house from the shop. I took the pressure valve and hose off and cleaned them. Tried it again. SOS. I bypassed the thermostat. Ditto. I've had it. If the service guy and Modine can't figure something out, it looks like I'm going to be a warm weather woodworker. And you are absolutly right. These guys have been great. Thanks guys


well, at least if I'm reading this right you're saying that you are willing to let the service tech call modine and try it one more time. Is this correct? If thats the case then 'get er done' as they say.

Good Luck! and keep me posted.

Brad

[Jim Sears]

OK..Here we go...

I have:
1) Had service guy check gas pressure while the heater is not burning and when it lights. Gas pressure is good.

2) Bypassed the HL switch. (by service guy)

3) Replaced terminal board (which has Time Delay Relay built on it) (by service guy)

4) Checked and cleaned Pressure valve and hose. (by me)

5) Bypassed thermostat (by me)

As far as I can tell, about the only things left in there are the 24v transformer and the gas valve.

Oh yea..I did find the flame sensor. It's buried way down on the lower burner. Didn't see it before.

[Jim Sears]

well, at least if I'm reading this right you're saying that you are willing to let the service tech call modine and try it one more time. Is this correct? If thats the case then 'get er done' as they say.

Good Luck! and keep me posted.

Brad

Yep. It's set up for tomorrow at 10:00AM. I have talked to Bob and to R.A. McGovern. Bob is supposed to call Pat McGovern and they are going to call Modine. Modine is supposed to walk him through checking everything out. Cross your fingers.:D

[Al Willits]

Doesn't sound like there's much left, I'm assuming the terminal board is the controlling module?

Maybe eradic power to it?

Let us know what happens

Al

[Ron Coleman]

Why this thing won't run right is really screwy. Here's the wiring diagram and schematic in case anyone has some sudden inspiration. It's pretty simple.

[Brad Noble]

Yep. It's set up for tomorrow at 10:00AM. I have talked to Bob and to R.A. McGovern. Bob is supposed to call Pat McGovern and they are going to call Modine. Modine is supposed to walk him through checking everything out. Cross your fingers.:D


Fingers are crossed! You know, if the combination of your local tech, the distributor in Columbus and Modine themselves can't get to the bottom of this then its time to buy another heater. And I know thats not an option at this point. :)

Good Luck Jimmy. Keep me posted.

Brad

[Al Willits]

Wonder if this thing has the honeywell smart valve, not the worlds greatest idea, kinda like putting the module and gas valve together.

Great on paper....

Good luck.

Al

[Brad Noble]

Yes, Al, I believe it does. And it might be the culprit but what I don't understand is how would it cause the fan to keep running but the burners to quit early?

Brad

[Rich Schneider]

I have two of the 75000 but Hot Dawgs (acutally one is a Modine and the other is a WGH - Hamilton Home products unit which is exactly the same down to each interal part..in fact the parts for my Modine came from WGH). It souds as though you have exhausted most of the major potential causes so far. I know you've talked to Modine, but I would strongly recommend talking to the people at WGH-Hamilton Home products especially given the steps you've gone through so far. They tend to be more homeowner/do-it-yourselfer friendly and really helped me a lot with my Hot Dawg when I was trying to troubleshoot a problem with the flame rollout switch kicking the unit offline. In my case the unit would fire up, run for a little while, then kick out. It turned out in my 75000 units that there are two flame rollout switches, one located at the top and one at the bottom of the burner tubes that senses if the flame for whatever reason leaps of flickers out of the burner tubes. I too at first would have to let the unit set for a while before restart. Then I realized that I could push the back of the switch in with the little button and refire the unit within a couple minutes. I could then watch the burners to see what was going on and noticed that the flame on the top tube didn't look to be burning exactly the same as the other ones. Pressure was checked on the high and low regulators (I have LP) and was fine. In my case it was a bit of debri that had lodged in the jet and was causing the flame to be a little bit erratic and after a bit it would utlimately trigger the flame rollout switch. The unit would then sit there running blowing cold air. Let us know what you learn since it will likely be very instructive for those of us who have similar units.

[Ron Coleman]

I just wonder if the replacement fan control board the service technician put in has something wrong with it. According to the schematic, the only thing that keeps the fan running is the closed contacts of the time delay relay. When the thermostat opens the time delay relay should keep the fan running for about 90 seconds and then turn off.

[Al Willits]

Yes, Al, I believe it does. And it might be the culprit but what I don't understand is how would it cause the fan to keep running but the burners to quit early?


Me neither, the burner going out is probable with the valve, but ya I'm not sure why the fan keeps going, in the circuit to the right, it looks like several wires going to the fan relay, but it doesn't look like any from the valve???

A exprienced tech should be able to eliminate the pressure switch, limit control and two flame roll outs easily enough, they should be able to read microamps at the sensor so they should be able to rule that out.

After that it looks like the valve is the only thing that controls the combustion air motor and ignitor.
And after that I'm not sure, it almost appears you have two problems going on here.
Be nice to attack this thing with a meter..

Tomm will tell hopefully

Al

[Dale Lesak]

The heat blower fan should run after the fire goes out. "Until the heat tubes cool down" Mine runs for about 45 sec to a min. before it shuts off. The fire shuts down, the exhaust fan runs for a short time and shuts down and when the tubs cool down the blower fan shuts down. I had a bad ground on the circuit board which was giving me the same problem you say your having. Mine had a striped screw hole. replaced the screw with a small machine screw and nut. fixed the problem.

[David G Baker]

Jim,
I don't know if this will solve your problem. I have the 75,000 BTU Hot Dawg in my pole barn that is natural gas fired. Every year when the weather starts getting cold I have to purge my gas line because my unit acts the same way you described. The burner will light for a short while but will not stay lit, I think that the gas to air mixture in the gas line is low on gas. I know that you said that you did purge your heater, but did you actually purge your gas line? I have a pipe plug in a tee and valve where my gas line enters my pole barn, I turn the valve off, remove the plug, then open the valve and let the gas flow for 10 or 15 seconds until the natural gas oderizer smells very strong. I turn off the valve, install the plug and wait for about five minutes until I am sure that all of the gas fumes have dissipated. I then turn up the thermostat and this solves my Hot Dawg problem. I have to do the same thing any time that my heater sets with out running for a long time.
Hope this helps.

[Ron Coleman]

Jim,
I don't know if this will solve your problem. I have the 75,000 BTU Hot Dawg in my pole barn that is natural gas fired. Every year when the weather starts getting cold I have to purge my gas line because my unit acts the same way you described. The burner will light for a short while but will not stay lit, I think that the gas to air mixture in the gas line is low on gas. I know that you said that you did purge your heater, but did you actually purge your gas line? I have a pipe plug in a tee and valve where my gas line enters my pole barn, I turn the valve off, remove the plug, then open the valve and let the gas flow for 10 or 15 seconds until the natural gas oderizer smells very strong. I turn off the valve, install the plug and wait for about five minutes until I am sure that all of the gas fumes have dissipated. I then turn up the thermostat and this solves my Hot Dawg problem. I have to do the same thing any time that my heater sets with out running for a long time.
Hope this helps.

Very interesting David. I have the 30,000 btu Hot Dawg and I have the same problem each fall when I first start it. I always figured it was maybe some dust or spider webs in the burners causing the problem. What I see is only one of my two burners will light and then the unit shuts down when it senses the other burner didn't light. I usually play around with cleaning the burners and finally after a bunch of false starts it works and never gives me a problem the rest of the winter.

My Hot Dawg is the only gas appliance at the end of a 150 ft run of 1 inch gas line. Maybe next summer I'll start it a time or two and see if that does the trick. I don't there will be any air in the line cause it's always under pressure but maybe natural gas gets stale or tends to separate just sitting in the line for months.

[Dan Barr]

You should put this thread in the OFF TOPIC section.

v/r

dan

[Al Willits]

To my knowledge, Nat gas supplies do not add air to nat gas, this probably comes from when they use propane during high useage times and propane being about twice as hot as nat has to be thinned down a bit, they use air then.

Not uncommon for air to work its way into a gas line while not being used for a period, what your probably doing is just taking that out of the system, bleeding the line is what your prob doing.

Shouldn't we be hearing from Jim soon? :)

Al

[Al Willits]

You should put this thread in the OFF TOPIC section.

v/r

dan

You could just ignore it too.

Al

[David G Baker]

Al,
I am not sure what is causing my yearly problem with the gas flow to my Hot Dawg but it happens every year with out fail. I bleed the line and everything works fine after that. I didn't think that air was getting in the line, but didn't know what else to say to describe the gas that wouldn't stay lit.

[Tom Leasure]

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,
Do you have a rubber hose going to the pressure switch ? One or two hoses ?? - If you do take them both off & blow them out - sometimes water will condense in them & not allow the switch to sense the correct pressure - this can drive the control board nuts - just a shot in the dark :rolleyes:

Tom