Mr Heater Big Maxx problems

[FlameOut]

I have the 45000 BTU natural gas model, and it has worked great the past few years, but the past few days I noticed it was acting up.

When the thermostat kicks the heater on, you can hear the one motor start up, then a few seconds later, the flame will come on, but then the flame will shut off after about 10 seconds, then the cycle starts again.

The LED on the board just flashes the steady slow flash indicating all is normal. I know these are known to have the circuit board go bad, but is there a way to know for sure? I was sure hoping to get more then three years out of this thing.

Bill

 

[regguy1]

Call their 800 tech line, they will warranty the circuit board even if out of original warranty time.

 

[stea]

Take a piece of scotch bright and clean the flame sensor. You may have to take off the gas manifold to be able to squeeze your hand in. I have to do that 1-2 times each heating season on the one in my wifes shop. Have not had to do it on the one in the garage.

 

[FlameOut]

Thanks for the tips. I'll give the cleaning a shot today and if that doesn't solve the problem, I'll give them a call. With the temps in the single digits last night, I hope I didn't have any problems with items freezing

 

[FlameOut]

I almost thought it was working properly this morning. I had the power shut off to it all night, and this morning when I tried it, it actually ran for about 5 minutes before shutting down and the LED flashing 2 flashes, which is System lockout - failed to detect or sustain flame. Current signal at FLAME terminal <0.6 microamps

Also, where exactly is the flame sensor? In this pdf file, what number is it?

 

[brawls43]

#4 on page 14-15 I think, even though they call it electrode sensor. Or you could trace the wire from the control board using the schematic on page 13. Both of those show the flame sensor.

 

[FlameOut]

Thanks. I think that flame sensor was the problem. Although I didn't take it out, I wanted to try something first. I used my air compressor and blew all of the dirt and dust out of the heat exchanger. I couldn't believe how much came out of there. I'm guessing the flame sensor was covered in dust. I turned the power back on, the thermostat up and it's still running 30 minutes later

 

[brawls43]

Probably. That's why Stea had recommended cleaning the sensor with scotch bright. Sometimes they'll get a coating on them of burned dust and such. Glad its working.

 

[bd8134]

My Sterling 45k propane heater last year came up with a flashing 2 lights and the same symptoms as you Flameout.
I put in a new flame sensor which fixed it and then over the weekend it started doing the same thing again. I took out my flame sensor and it had some baked on white hard deposits. I cleaned the original sensor and put that back in and it has been great since. You will not be able to clean those deposits off with compressed air if your sensor is coated, but maybe in your case the burners were not lighting properly.
Interesting stea that you can just clean the sensor, I will try that in the future if it happens again. I was putting off getting another sensor as it ~$50.

 

[FlameOut]

If it ever stops working again, I'll be sure to pull that sensor and clean it before attempting any other repairs. These forums are great! Someone always seems to have an answer for any problem

 

[nmcqueen469]

How has no one mentioned the irony of OPs username?!?

 

[stea]

Interesting stea that you can just clean the sensor, I will try that in the future if it happens again. I was putting off getting another sensor as it ~$50.

Yea, I dont know what causes it but each time I clean it im usually good for 3-4 months.

 

[FlameOut]

I spoke a little to soon. Went out in the garage this morning and right away noticed it was colder than it should be. Looked at that LED at it was doing the 2 flashes again. Reset it, turned up the thermostat and flame only stays on for a few seconds Time to pull that flame sensor

Edit: Just went out to pull that flame sensor. Wow, what a poor design. They make it so you pretty much have to dismantle the entire heater to get at that thing. You would think they would have the screw heads visible so that you didn't need to remove the entire burner enclosure to get to it. I sure hope the flame sensor is the problem

 

[Duckfamily]

Finished install of Mr. Heater Big Maxx this morning. The unit fired right up, everything was set. It ran up from 53º to 60º the shut off. When it called for heat the next time the unit ignited, ran about 5 seconds, flame went out. Did this three times and went to lockout. 2 flashes. tried several times. Cleaned flame sensor, checked all ground connections etc. Any suggestions would be great.

 

[Showkey]

Watch the flame is it traveling from burner to burner smoothly towards the flame sensor ?

Gas pressure checked and at spec ? Low pressure would effect the flame travel and timing to confirm the flame sensor.

 

[Duckfamily]

Thanks for the response Showkey! Excellent flame travel burner to burner, right across flame sensor. pressure is to spec. Called Mr. Heater today. The best customer service department I have EVER dealt with. They walked me through several trouble shooting tips. Sending a new flame sensor to start with. I will keep you updated.

 

[John Smallberries]

Hi all!
Has anyone heard of the exhaust fan on a Big Max heater simply running too slow? Mine runs, but does not trip the pressure switch. It is also so quiet, I cannot hear it turning. I pulled it apart and ordered a new motor.

My initial complaint was intermittent heat with no LED indication. The unit would turn on and heat for 5-10 minutes, then shut off. The green LED was off: no flashing, nothing. This would seem to indicate a problem with power (transformer) or the main circuit board. I replaced both of them.

With the new parts in place, the LED is flashing 3 times, indicating a problem with the vacuum switch. When I pull vaccuum on the hose, the code clears and it fires up - so it is not the switch. The ****** where the hose attaches is clear.
This is when I took a closer look at the exhaust fan and noticed that it simply is not running "strong". I pulled it out and found the impeller to be a bit rusty. The motor spins, but I can stop it easily with one finger. I have a new motor arriving today - I'll report if it spins faster.

If I am right, the weak fan allowed the heater to run, but let the circuit board and transformer get very hot (it provides the only ventilation air flow). Hot circuit boards are bad.

For good measure, I'll take this chance to clean the flame sensor. My garage can get very dusty (kid sanding and painting his car!).

 

[John Smallberries]

All good now. My new fan and motor assembly arrived today. I wired it up on my bench and it ran as expected: you wouldn’t stick your finger in there. It blows hard. I work with an electric
Motor design guru and he explained the most likely issue. Single-phase, 110-volt motors have two separate windings. One initiates rotation to start the motor. The second provides the primary motor torque. My primary winding likely developed a wire break. Only the starting coil was working - hence slow speed and low torque.

I learned that it was a bit cheaper to replace the fan and motor together than just the motor. This unit is only 3 years old and the impeller was already very rusty. I threw some Rustoleum on the new one.



Sent from my iPhone using Tapatalk

 

[John Smallberries]

OK - I now have a new circuit board, new transformer and new fan. The fan was clearly bad - but I'm not sure about the rest. The furnace fires up fine with no flashing codes. It runs hard for ~5 minutes and shuts down. After another 5-10 minutes, it fires right back up. During this down time, the LED is completely off. This was the initial symptom I was trying to diagnose and thought I had a bad circuit board. Is it normal for the LED to go fully dark? My garage is heating up OK, but I'm puzzled by this on/off behavior.

 

[John Smallberries]

I went to the Mr. Heater website and chatted with Tech Support. That green LED should never be completely dark. The tech suggests a new circuit board. I did just replace it, but I admit it that I did not order it directly from them (SKU #60105). So - another one is on the way. In the "I'm a dumb-***" category, the OE board directly from Mr. Heater was only $60 - about the same as the Google Search board I bought first. I'll compare them side-by-side when the OE board comes in.

 

[John Smallberries]

So - I got the "official" Mr. Heater Big Maxx control board. It looks identical to the one I had. Even the "QC" ink stamp is in the same spot. I swapped it out and still have the same issue: Runs great for 3 minutes with fast-blink LED, then shuts off with a dark LED. Wait 5 minutes and it fires back up, repeat. So - I do have heat in my garage, but something is still not right. I have also lost the link to the online Mr Heater customer service chat - so I'll call live again today. Anyone have ideas? Remember that I am on my 3rd control board, new transformer and new exhaust fan. I will clean the flame sensors next (haven't done this yet), but can't see how a bad flame sensor explains my symptoms.
BTW: I added a small computer cooling fan to the housing to ensure the board isn't overheating. It NEVER shuts off, so I know the 110-volt power to the unit is OK.

 

[Showkey]

John, I would slow down a bit.
I don’t have a Big Max but my furnace and shop heater only lite the LED when its calling for heat or running.
Sounds like your heater is running for 5 minutes.......so it’s not the flame sensor.
Sounds like your heater is not flashing error codes at the LED.

The cooling fan would keep the roll out switches cooler if the unit is slight over fired or the flame is rolling out of the burner/exchanger tubes. If the roll out switches are tripping there should be an error code flashing.

So could it be after 5 minutes the wall thermostat is satisfied, then the cool air in the shop circulates, the thermostat kicks back on and calls for heat ?
The whole process would repeat until the entire shop is warm. ?

Location of the thermostat, size the heater compared to the shop size and the initial set temperature of the thermostat would play a part in the above scenario.

 

[John Smallberries]

It has to be the transformer. Mr. Heater is sending me out another one under warranty. I did replace it just 2 weeks ago - but it was not directly from them. It also fits the symptoms. I verify 110 V on the upside, but don't see 24 volts on the blue/yellow pins when the LED is dark. When the LED comes on, I probe the output of the transformer and see 24 volts. An intermittent short in the transformer that opens up when it gets hot is the most likely cause. BTW: I pulled and cleaned the flame sensors for good measure - they had a very small amount of brown residue on them. Not the root cause - but a good preventative measure.
I found my link to the online Mr. Heater chat and had a live person on the phone at the same time - these guys are very helpful.

 

[John Smallberries]

Per Mr. Heater, the LED should flash slowly when it has 24 volts and no request for heat. It should flash fast when it gets a request for heat. They agree that the LED should never be dark whenever 24 volts is present. Their first diagnosis was "bad board" with the symptom of "dark LED".

 

[John Smallberries]

John, I would slow down a bit.
I don’t have a Big Max but my furnace and shop heater only lite the LED when its calling for heat or running.
Sounds like your heater is running for 5 minutes.......so it’s not the flame sensor.
Sounds like your heater is not flashing error codes at the LED.

The cooling fan would keep the roll out switches cooler if the unit is slight over fired or the flame is rolling out of the burner/exchanger tubes. If the roll out switches are tripping there should be an error code flashing.

So could it be after 5 minutes the wall thermostat is satisfied, then the cool air in the shop circulates, the thermostat kicks back on and calls for heat ?
The whole process would repeat until the entire shop is warm. ?

Location of the thermostat, size the heater compared to the shop size and the initial set temperature of the thermostat would play a part in the above scenario.

Thanks for your thoughtful reply!!! I have seen the roll-out switch fault last year when my burner screens plugged up. The flame was, indeed, rolling out where it should not be and the switches worked as advertised. This is not the case now as the screens are clear and the blue flame stays where it is supposed to. Also, I have no diagnostic flashes (I believe three flashes is a tripped roll-out switch), just a dark LED. Let's see if the transformer fixes the issue. The good news is that I have SOME heat in my main garage. I have a smaller wood shop adjacent to the big shop with a fully-functioning heater. I put a fan in the doorway to help move some of that heat into the main garage while I sort out the problem. Thanks again for taking the time to respond. I love Garage Journal!


BTW: the main garage heater shuts down while the thermostat is still calling for heat.

 

[John Smallberries]

Having said all of that - it is still fishy to me how I could have two bad transformers and a bad exhaust fan motor. It sure seems like I'm winning the "bad furnace luck" lottery. It is still possible that I am simply missing something obvious. The transformer will be here in 3 days.

 

[John Smallberries]

I am putting a 3-amp inline fuse in the secondary of the new transformer. I don’t want my bad root-cause analysis to toast a third transformer


Sent from my iPhone using Tapatalk

 

[John Smallberries]

I have also read that a short in the wiring to the thermostat can also cause problems with the transformer. I have been using one thermostat to control two different heaters - which is not ideal. This is a good chance for me to split these and get a new "old school" Honeywell round dial heat-only thermostat and a new wiring run.

 

[Showkey]

I have also read that a short in the wiring to the thermostat can also cause problems with the transformer. I have been using one thermostat to control two different heaters - which is not ideal. This is a good chance for me to split these and get a new "old school" Honeywell round dial heat-only thermostat and a new wiring run.

Oops !
Less than ideal is putting it mildly.......That maybe the root cause of your problem or failure of prior installed parts.

Do both units have there own 24 volt power supply ? The shared t stat could allow one heaters wiring to back feed power to the other unit when it calls for heat.

 

[John Smallberries]

Oops !
Less than ideal is putting it mildly.......That maybe the root cause of your problem or failure of prior installed parts.

Do both units have there own 24 volt power supply ? The shared t stat could allow one heaters wiring to back feed power to the other unit when it calls for heat.

Agree. It was stupid to have one T-stat and 2 heaters. I have them separated now with new transformer, new T-stat, new wire run and all seems to be working fine.

 

[resq302]

Hello,

New to the forum and I’ve had to replace my circuit board in my Mr Heater Big Maxx 50,000 btu heater now twice. The unit is about 2 years old and the first board went the beginning of November. It kept blowing the 3 amp fuse. Not realizing it was under warranty still, I purchased a new one, same part number and everything. A few days ago I smelled something in my garage and realized the heater was not working or even turning on. This is what I found when I opened up the side cover. Is there any recalls for this heater? Why did it do this? Enter I sent me another board but I am worried as my antique car is in my garage and don’t want to lose my house or my car to a fire.


Sent from my iPhone using Tapatalk

 

[resq302]

As you can see from the previous pic, it melted the insulation off the one wire.


Sent from my iPhone using Tapatalk

 

[resq302]

Back side of the board and there is even some soot stains on the metal plate where the board attaches too. Weird thing is that it worked for two months before this happened.


Sent from my iPhone using Tapatalk

 

[D45]

Wow that is crazy, and scary

Did you contact the manufacturer and explain to them what happened????

 

[Mopan]

I have a problem maxx heater garage blower kicks on for about 10 seconds then shuts off can anyone help... new to forum
mopan

 

[spudley]

I have a problem maxx heater garage blower kicks on for about 10 seconds then shuts off can anyone help... new to forum
mopan

Sounds like it could be your flame sensor but it could be other issues. Is the LED error code blinking? Your book should have a listing under troubleshooting of what the flashes indicate.
Search these threads for many posts re: big maxx problems or type "big maxx led codes" in google. Lots of GJ posts come up.

 

[resq302]

Wow that is crazy, and scary

Did you contact the manufacturer and explain to them what happened????

Yes, they sent me another board. Still wonder why the 3 amp fuse didn’t blow.


Sent from my iPhone using Tapatalk

 

[Showkey]

Yes, they sent me another board. Still wonder why the 3 amp fuse didn’t blow.


Sent from my iPhone using Tapatalk

A high resistance (loose) connection will over heat the board and not blow the fuse.
A shorted component or wire down stream may not be protected by the fuse.
It would be important to check what devices are powered or switched by the board in the area of the failure........to determine why the board failed. Or the new board might smoke in the same way for the same reason.

The board failure in smoke is NOT a rare occurrence.

Another example the inducer blower bearing failure might cause excessive current draw above the relay capacity causing the failure.

 

[Duckfamily]

An update on my problem. Mr. Heater customer support was unmatched! First, they were quick to get back to me, very knowledgeable and helpful. No questions asked sent me the parts I needed and everything is up and running great.

Turned out it was the circuit board and when replacing I notice bad solder joints on the original board. THANKS MR. HEATER!!

 

[resq302]

A high resistance (loose) connection will over heat the board and not blow the fuse.
A shorted component or wire down stream may not be protected by the fuse.
It would be important to check what devices are powered or switched by the board in the area of the failure........to determine why the board failed. Or the new board might smoke in the same way for the same reason.

The board failure in smoke is NOT a rare occurrence.

Another example the inducer blower bearing failure might cause excessive current draw above the relay capacity causing the failure.

Interesting point on the loose connector. I wonder if the connector at the board loosened up. It was right at the “accessory” spade connector where it seemed to start.


Sent from my iPhone using Tapatalk