422 Overheating

[dan in maine]

Don't know what went wrong but here's the scoop.

Had an issue with my 422 shutting down after start up. It would run for a while then I'd get the 88:88 blinking lights then shut down.

It's a nine year old heater and the flame was pretty much yellow all around so I removed the heater chamber assembly and changed the mat and ring and a few gaskets and all looked good.

Now, after it gets up to temp it overheats. Hot to the touch on the outside like I never felt before. It seems that now the air circulation fan doesn't kick in until it's too hot, then it's too late. I put a jumper wire across the fan thermostat and it will run fine for as long as the thermostat is bypassed (had it on for a few hours with no problem). I installed a new fan thermostat and it still overheats without the fan kicking in. When I put a jumper across the new thermostat it seems to work fine for as long as the jumper is in place. Of course, I won't leave the jumper on when the heater is unattended.

Any suggestions?

[HayZee518]

yellow flame

a yellow flame indicates a blocked air intake or a combustion blower on its way out. inadequate combustion air doesn't allow complete combustion of the kerosene and so it soots up the inside of the pot.
88:88 indicates a lockout or an interruption of unit power.
If it was anything other than 88:88 it would show which lockout was activated. E-13, E-14 would be starved for fuel or no flame as in a flamerod malfunction.
When the unit starts, the combustion blower [fan] is the first to start and the last to shut down in all monitors.
It has two bearings no: 608Z bearings, same type as used on inline skate axles.
Monitor charges an arm and a leg for them but you can get a half dozen from a supplier on eBay for around eleven bucks.
The blower motor is screwed to the housing and the motor itself is riveted together. grind down the three rivets and open the motor. use a small bearing puller to remove the bearings.

[dan in maine]

Hi HayZee, thanks for the reply.

The combustion fan is working fine, it comes on first and stays on last like it should. All my air intake and exhaust hoses and channels are clear, no blockages. The combustion blower motor spins free and quiet.

The fan thermostat that I jump is for the Air Circulation Fan, the one that blows hot air into the room. That fan isn't coming on soon enough and the chamber is getting too hot and overheats. As long as the air circulation fan is blowing air past the chamber the unit seems to work fine. Even with a new thermostat I have to jump the thermostat to keep the fan running or it will overheat. I hope it's not an issue with the printed circuit board but I don't know. I read somewhere that the 88:88 will come on when the unit locks out for overheating.

After I replaced the mat and ring, the flame is good now, nice and blue with a slight yellow tip here and there.

My question is, "Why does the unit run fine when I jump the air circulation fan thermostat but not when I remove the jumper?" This is a new thermostat.

I'm stumped.

[HayZee518]

fan thermostat

what is the temperature rating of the "stat" and is it normally open. it should be normally open until the plenum temperature reaches its set point, at which time its contacts should close.
if you got a sensor that is normally closed then when it reaches the setpoint it will open.
which explains to me that is why it works when its jumpered out.

[hawkins111]

wrong fan thermostat

As was previously stated the Fan Thermostat is a normally open switch (part number 6260). If you had just misplaced one of the Over heat thermostats for the Fan thermostat the fan would come on immediately when the stove was turned on. The other thing that would happen is the fuel pump would never come on as there would be an open thermostat switch in its circuit. Since you can jumper the Fan thermostat and the stove works fine, your fuel pump circuit is OK and the fan circuit is OK except for the thermostat. Some how or other you have the wrong Fan Thermostat. Find a good Monitor dealer and get the correct thermostat. The 88:88 shows when the stove shuts down because you have never set the clock. It can also show if there is a power lose or a main circuit board malfunction. Your M 422 has a limited number of error codes. It does not have the E13 or E14 codes of the newer M2200. You have to interpret the code or lack of a code on the M422 models. An over heat or lack of fuel on a M422 would show you the time and flashing status lights. With no clock set you would see a flashing status lights and 88:88 in the clock window. I think you have the wrong thermostat installed in the fan circuit.

Tom

[adnadeau]

I don't think it's the thermostat. The circulation blower on my 441 runs fine with it disconnected. This is the single one on top of the heat shield with the orange dot. I think that's an overheat protector. If you check the schematic and the normal timing diagram, you'll see IC7 controls the blower and it turns on 5 min & 50 secs after the ignitor relay clicks on. I measured 5min 48 secs with a kitchen timer. If you look at the troubleshooting flow chart Item 9 it implies the PWB is bad.

[hawkins111]

422 circulating fan circuit

Adnadeau is correct in the fact that the fan will run with the fan thermostat connector removed from the board. On page 3 in the Description section it states, “Operation of the fan is controlled by the microprocessor and fan thermostat switch”. Page 34, Operation Timing Chart shows no power to the FM for the first 5 or 6 minutes of the cycle and a power cut after 3 minutes after flame lose. The Timing Chart does not show the Fan Thermostat. The main circuit board will turn on the circulating fan after 5 minutes or so and turn it off after 3 minutes of flame lose with out the fan thermostat. After shut down the main board will apply power to the fan thermostat to take care of any chance of overheat. The power remains there through out the start up to take care of any chance the combustion chamber gets too hot too soon. As Adnadeau states, the cause is more likely the main board than the thermostat. Use your volt meter and measure connector D red to black on High 110VAC, on Low 93 volts. If there is a problem with the PCB contact, Mathis Electronics in NC. They will fix your board for a fair price.

Tom

[dan in maine]

I want to thank everyone for their input and suggestions. I'm late replying because I have to work this weekend and getting home late.

After all I have checked and read on this site, I'm leaning towards the PCB. I replaced the air circulation fan thermostat with a genuine Monitor part # 6260 and still have the same problem. I know I did not mistake one of the overheat sensors for the fan thermostat but I see how someone could. Both the old and new thermostats are normally open and will close when hot (I don't know at what temp but they do open and close). With the thermostat connected, the heater will get just to the point of overheating and then the air circulation fan will kick in but by then it's too late and she goes in to overheat/lockdown mode.

With the thermostat jumped everything seems to work fine, no issues with fuel supply and the electronic temp controls work like they should. Of course the fan is running all the time.

The service manual I received through this forum was a blessing and a big help but like some .pdf files it's blurry in some places. Some of the the small print in the schematics, timing chart and troubleshooting section is almost impossible to read. It's also missing sections 1-15 thru 1-19 which cover the air circulation fan.

I appreciate all the help and if you can think of anything else I may be missing please let me know. You guys are great. Also, if anyone can provide a clear copy of the blurry sections of the manual and sections 1-15 thru 1-19 that would be great to have. Thanks.

Dan

[HayZee518]

diagram

if you can find a user ADNADEAU he took apart the whole flow chart and re-printed it in a standard high resolution chart.

[adnadeau]

Monitor service manual drawings

These are zip files with PowerPoint inside, I think. One is a pdf.
Nope; they're all pdfs.

Pg 3 of the scanned service manual is missing. It contains sections 1-15 through 1-19. I've scanned it in, but I can't seem to shrink the file size enough to post it here.

[adnadeau]

Page 3

Here is a jpg of the service manual pg 3. I hope it comes out large enough.

[dan in maine]

These are zip files with PowerPoint inside, I think. One is a pdf.
Nope; they're all pdfs.

Pg 3 of the scanned service manual is missing. It contains sections 1-15 through 1-19. I've scanned it in, but I can't seem to shrink the file size enough to post it here.

Thanks adnadeau,

I'll print these off tomorrow and see what I can figure out. Thank you for all your help.

Dan

[dan in maine]

Problem Fixed and Kudo's to Mathis Electronics Inc.

The problem was in the PCB. I have no idea how or what went wrong. As you can see from this thread, the air circulation fan wasn't coming on and the unit was overheating. After exhausting all possibilities, I sent my PCB to Mathis Electronics in North Carolina. They replaced a relay and an IC (whatever that is) and the heater is running fine.

I'm very impressed with Mathis and highly recommend them if you have PCB issues. They advertise a 72 hour turnaround time on their work. For me they did a lot better than 72 hours. They fixed my PCB and had back in the mail the day after they received it. Total cost of the job was $138.00. They also give a 3 year warranty on their work.

I again want to thank everyone else on this board who gave advice and sent files and information. For anyone who owns a Monitor, this is the place to be.

Dan

[HayZee518]

board

the IC is an integrated circuit, a computer chip, maybe rectangular or square that operate the fan relay.