Modine Hot Dawg Issues

[brianthomas]

My Hot Dawg sits for days at a time unused as the garage is usually only a weekend experience. When I bump the thermostat up for the heater to run it goes through it's cycles but does not start the circulation fan blower soon enough. It used to start the fan about 30 seconds after the burner ignited but now it waits over a minute and the burner gets too hot and kicks off the gas. The gas will come back on when the heat exchanger cools down a little which only takes a very few seconds. I would love to fix it myself and came up with possibly the "time delay relay board" as the culprit. It only does this on the initial start up and not on the cycling restarts when I am working in the garage.

Any thoughts as to if I could be on the right track?

 

[regguy1]

My Mr Heater had some issues shortly after installation, it was the circuit board. They sent a replacement out fast and all is well since then. Modine should have an 800 number for tech issues.
See my heater in the video link below....

 

[bd8134]

Do you have any error lights flashing when this happens?

 

[nehog]

Bump thermostat from what temp to what temp? How cold was it?

 

[brian thomas]

I don't see any place to look for an error light unless I need to take the control panel off first. I use an old style mechanical thermostat and am usually going up from around 50 or 55 degrees to the high 60s. I'm starting to think maybe the flame sensor is bad as the first cycle is usually for 1/2 hour run time to bring the garage to temp then it works fine untill it sets for a few hours. After a few hours sitting idle it will delay the blower simply too long. I noticed since new the blower took longer to come on on the first cycle of the day. After the first cycle it took less time.

Thought, is it a timer or sensor input as to when the blower comes on?

 

[jwith68]

Try cleaning your flame sensor. They will sometimes get a hard, white-ish oxide latter on them that "insulates" them just enough that the control board will think the burner is not lit, causing exactly the behavior you are describing. Just polish it up with emery cloth, and give it a try - costs nothing but 10 minutes of your time.

 

[bd8134]

My flame sensor was dirty like jwith68 mentioned. Cleaning made the unit fire correctly each time but I did replace it as I was worried it would fail. This was a Sterling heater with flashing 2.
I found this in one of the manuals on the Modine website but it may be different for your model..
"Upon a call for heat from the thermostat, power is supplied to the power exhauster motor. The unit will go through a purge period and then the direct spark igniter will be energized. At the same time, the main valve in the combination control valve will open to allow gas to flow to the burners. If the fan motor has not all ready started it will start shortly. If a flame is not sensed for any reason the main valve will close and there will be a short purge period before ignition is tried again. If the flame is not sensed after four tries, there will be at least a one hour wait before ignition is tried again."
In the purge period above my heater would kick in the vent motor for a while.
On this one it also said..
"Control board LED flash codes vary with control type. A decal is installed in the unit giving a brief description of the applicable codes for the heater. For more detail, see the control board data sheet included with this manual."