441 circulator fan runs constantly

[72cougarxr7]

I just purchased a used Monitor 441 from craigslist to heat my garage.
The previous owner had it in a little workshop, it was unhooked when I came to look at it so I could not test it. I plugged it in when I got it home and the second you plug it in the circulator fan comes on (low speed). Upon taking the grille off, I discovered a mouse had made his home in there and chewed up a couple wires. I repaired the wires but the fan still runs whenever the unit is plugged in. Any ideas what the problem could be? I have a digital multi meter and some basic wiring experience but can not figure this out.

[hawkins111]

circulating fan

Cougar,

You have a shorted or improperly wired fan thermostat switch. This is the C connector with Red wires on the main board. The switch in that circuit should be normally open. As the stove heats up it closes the switch and the fan comes on. When the stove shuts down the fan will cool the chamber and the switch will open and shut off the fan. See the attachment for proper wiring.

Tom

[72cougarxr7]

Ok, checked the fan thermostat switch, it is not open at room temp.
According to my parts diagram, it should be part # 6464.
Do I have to order this from a dealer or is there an online source?
Thanks for the help so far!

[72cougarxr7]

On second check, i unplugged one of the fan thermostat wires to simulate an open circuit, plugged in the unit and the fan still came on instantly.

[HayZee518]

something still messed up in your fan circuit. the plenum switch actuates a point on the main heater board. this provides the two speed levels to the fan. double check your wiring. ebay has parts for vented kero heaters.

[72cougarxr7]

Double checked all the wiring and everything else looks ok.
Is it possible this could be a circuit board problem?
It looks like there are 2 black boxes on the circulator can circuit, one is to the right of the 3 wire blower fan connector, this one is open.
The other is in position "C1" towards the bottom left of the board, this one is NOT open.
is this "C1" box supposed to be open?

[hawkins111]

fan circuit

Cougar,

You stated the fan thermostat was “not open” at room temp. That means it is closed and that is not right. The fan thermostat should be connected to the C connector on the Main board with red wires and that circuit is a normally open circuit. There is only one switch in the fan circuit. You also stated you disconnected the wires from the fan thermostat and the fan still came on. Is there a chance the red wires are connected to the wrong switch? If the wires are correct and the right switches are in the right place then there is a problem with the main circuit board. Use your cell and take a picture of the fan switch and the over heat switches.

Tom

[72cougarxr7]

The red wires are connected to the fan thermostat and as far as I can tell all the wires are in correct locations.

[hawkins111]

normally open

Cougar,

When I say Normally Open Circuit, I mean the switch on the heat baffle is open at room temp. You should be testing the little round switch not anything on the circuit board. There are three round switches. Two are for over heat and they are normally closed. One switch is for the fan and it is normally open. It is very easy for someone to mistake these switches as they look very much alike. Remove the connectors and test each switch and find the one that is open. That is for the fan. Keep us posted.

Tom

[72cougarxr7]

OK, double checked the switchs. The overheat switches are both closed. When I checked the fan switch, I unkhooked both wires and tested, it is open. When I plug the wires back in and check it is closed! I am thinking that must mean I have a short in the circuit board?
Thank you so much for the responses!

[hawkins111]

test that heater

Cougar,

It does appear you have some problem with the main board. This means you need to experiment with the stove to see if it is worthwhile to continue with it. Remove the C connector or the D connector, which ever will stop the fan and try to start the stove. You need to confirm the blower assembly, fuel pump and igniter. Once the stove starts and runs for a short time plug the fan back in. If the stove runs you can look at the flame to see what you have. The cost of a main board is around $450, Igniter $120, Burner ring $85. If a new burner pot is needed it will be around $250. Depending what you plan to heat you may be better off getting a smaller new heater, rather than rebuild your older Monitor. Keep us posted with your progress. It is always nice to see the complete story.

Thanks,

Tom

[72cougarxr7]

I spoke with Dima from Mathis Electronics (they specialize in rebuilding the circuit boards) and was told this is a common problem. Said they just repaired one a couple weeks ago with the same issue. They can repair for around $100.00 , so I think that is the rout I will go.
I will post back and let everyone know how it turns out.
Thanks for guiding me along the trouble shooting so far!

[HayZee518]

if you go to ebay and just type in "monitor heater" a list of about 70 entries pops up. a rebuilt board here shows $149 and change.

[72cougarxr7]

Monitor fixed!

I send the circuit board to Mathis Electronics. They fixed it for $100, only took a few days to repair. Got it back today, put it all back together, and ran for about an hour to test everything. Its working great now.