Another Mr. Heater?

[Deltarat]

I have a 75,000 Mr heater and it worked fine for 3 months. Now the burner will kick on for a sew seconds and then cut off. It will do that a couple of times and then just quit. I can cut the thermostat off and back on and it will kick on and off again. I thought it might be the the thermostat, so I changed it and it does the same thing.
It is hard to warm up the shop with it not staying on. Any suggestions?

 

[larry4406]

The following is based on experience with typical gas furnances. I do not have a Mr. heater and have never worked on one.

Check your flame sensor. Typically this is a metal round object thinner than a pencil and the flame impinges on it. It detects the flame and allows the gas valve to stay open. If it thinks no flame is present, it shuts the gas off. The computer board's typically allow 3 attempts and then go into lock out. You have to kill power to reset the board to try again (this is what is likely happening when you kill the t-stat, although I always had to turn off the power). Reposition the sensor fully into the flame by bending the bracket, also check its wiring. You may also want to clean the sensor exterior - you may have **** on it from the garage environment that affects its sensing ability.

Some computer boards have a red light on them. They blink in patterns to help diagnose a problem. Check your owner's manual for the codes.

 

[rickairmedic]

Larry hitthe nail on the hed with the flame sensor . While your checking it take it out and sand it with some sand paper so it is shiny again and put it back in probably 8 out of 10 service calls I run in the winter for no heat are dirty flame sensors.

Rick

 

[Deltarat]

I emailed mr heater and they said it sound like a circuit board. They said they would send me one for free and never asked when I bought it or where or any sales slip.
Good service.

 

[sgo70]

I had a similar problem with my Modine overhead. Everything worked fine but the fan wouldn't kick in so it would shut down on the overtemp limit. It ended up being the circuit board as well. I've been reading a lot of posts about these boards crappin' out.

Sean

 

[mdoolittle]

I have the same problem also. They sent a sensor out first, but that didn't do it. I have a new board on its its way. Very frustrating when ya spend more time working on your heater than on your project.

 

[BigChevy80]

I had a similar problem with my Modine overhead. Everything worked fine but the fan wouldn't kick in so it would shut down on the overtemp limit. It ended up being the circuit board as well. I've been reading a lot of posts about these boards crappin' out.

Sean

Seems to be a common problem with these Mr. Heater units. My brother in law is an HVAC service tech and he said he's replaced quite a few of them.

The board is probably made in China... nuff said.

 

[Deltarat]

Circuit board came in today and it seems to have fixed the problem.

 

[Shocker]

I wonder if I should just get a board now for my yet to be installed 45k btu unit.

 

[Deltarat]

It would be nice to have a new one on hand. Before next winter I may order one to have just in case. They must be fairly cheap, because they didn't ask any questions. They just took my word that I bought it 3 months ago and sent me one.

 

[Junkman]

try swapping out the good board for the original one, and see if it still works. There is a strong chance that it was just a loose connection. This was the problem with mine, and I realized it when I swapped the board for the second time. Now I have a spare, but don't use the heat in the garage, since there is no more room to work. Need a bigger garage!!!!

 

[Deltarat]

I put the old one up and if I have trouble I will try it. I didn't notice anything loose when I replaced it, but that does not mean that there wasn't.