Help with Digital Thermstat Mod

[dkutz]

So I know many have replaced the facorty digital thermostat on the Coleman/fleetwood with a digital one.  From what I can find the LUX DMH 100 and LUX TX500 will work.
 
Is there any other suggestions?  DOes anyone have pics of how to do this, wire the new one etc?
 
Mine heater does not work, so I thought I would start with the crappy factory thermostat

[Recumbentman]

Dieter
Take a look at my thermostat mod in my mods page below. If you go with the cable extension, you could use any 12/24v thermostat unit you find. very easy mod.
I would first pop off your heater grill and check the reset button on it before installing a new T-stat. Sometimes they will have to be re-set to start working again.

Brad

[dkutz]

Dieter
 
I would first pop off your heater grill and check the reset button on it before installing a new T-stat. Sometimes they will have to be re-set to start working again.
 
Brad

If I knew where that was.  I have looked at the manual and its really not much help....  THe thermostat is only $25 and I would replace the stock one regardless, it sucks.

[wavery]

If I knew where that was.  I have looked at the manual and its really not much help....  THe thermostat is only $25 and I would replace the stock one regardless, it sucks.

The thermostat is just a "Switch". It has 2 wires. If you touch those wires together the switch is closed and the furnace should go "ON". If the fan does not run when you turn on the furnace at the thermo, pull the thermo off and touch the 2 wires together. If the fan runs, your thermostat is bad.

If the fan runs when you turn on the thermostat but the igniter doesn't light the furnace, the thermostat is not the problem because it is closing the circuit and that's all the thermo does. Everything else takes place in the furnace.

If the fan comes on and you don't hear any "Clicking" sound, the igniter may be bad.

If the fan comes on and you hear "Clicking" (for a short time, then stops) the igniter is OK but you may have one of the following problems:

* Low voltage at the heater control. (Usually caused by a corroded connector or bad wire between the thermo and the heater)

* Bad ground

* Clogged exhaust air passage (could be carbon build-up a dead mouse, wasps nests etc)

* Defective "Sail Switch" (this is the switch that detects air flow in the exhaust chamber. if the sail switch is bad, it will not signal the gas valve to open)

* Stuck or defective "gas valve solenoid" (sometimes a good wrap with the handle of a metal butter knife will dislodge a stuck valve, often the valve may need to be replaced)

* Blockage or bent propane supply pipe. (Shut off gas and replace pipe)

* Defective "main control board" (Check board for a glass fuse, replace fuse or control board)
 
I would suggest starting by checking the fuse on the control board (if there is one) then check the exhaust for obstructions then make sure that there is a secure ground from the heater to the frame (even if it means running a separate wire). Then check the voltage coming into the heater. Lastly, try turning on the propane tank and loosening the propane connector until you hear hissing......no hissing means bent or plugged pipe. if you get hissing, you have fuel.

Failing all that, I would suggest taking it to an expert. If you start replacing parts, it could be an expensive exercise that could still end up with no solution. Chances are, an expert could fix it in less than an hour with minimal to no cost (if it's something stupid simple).

[dkutz]

Thanks Wayne. I guess I will look at it again next weekend. I looked at it before, but quit honestly, I don't know what I am looking for. Sail switch etc, its all a mystery and the digarams don't seem to help. Hell I had heard that there is a switch on the heater as well, I didn't see that when I looked either....
 
Last time I tried it it did not do anything.  no fan no nothin.  At least before the fan ran with no heat etc...
 
Next week...

[wavery]

Thanks Wayne. I guess I will look at it again next weekend. I looked at it before, but quit honestly, I don't know what I am looking for. Sail switch etc, its all a mystery and the digarams don't seem to help. Hell I had heard that there is a switch on the heater as well, I didn't see that when I looked either....
 
Last time I tried it it did not do anything.  no fan no nothin.  At least before the fan ran with no heat etc...
Next week...

If that's the case, it could be a bad wire from the thermo to the heater or a bad contact at/in the thermo itself. If it was just bad enough to send low voltage to the heater, the fan could have run but the gas valve would not have opened unless the voltage was >12.2V (I think) with the fan running. It could be that either the weak thermo has totally failed or there is an open circuit in the wire itself.

I would still not start replacing parts until I performed the tests that I described above.

To test the wire from the thermo to the heater, find the 2 wires coming into the thermostat from the heater (I think they are white and red but check the colors at the thermo). When you find where those 2 wires connect to the heater, run a good jumper wire direct from one connector to the other. If the heater comes on and lights, replace those 2 wires. Be sure to use the same color and gauge wire (they are the same wires used for automatic yard sprinkler timers....in the garden dept @ HomeDepot). If it still doesn't work, install a new thermo.

Before you do anything though, take the front panel off of the furnace and find the brown (I think) "ON/OFF" switch in the front of the furnace (right in front of your face) and be sure it is in the "ON" position, the battery switch is turned on, the battery is fully charged and the PU is plgged into the house.

Print this out and take it to the camper with you. It may help:
http://www.atwoodmobile.com/manuals/furnaces/MPD%2032072%20SP%201.08.pdf

If that doesn't work, invite the previous owner for a BBQ and maybe he'll help you......if you're nice.

NOW!!!!! having said all that.......if he gets there and finds something really simple, that I've already described, I would suspect that he might just have a very interesting post on PUT.......

[dkutz]

well I will check it out again at San Clemente and then hot wire the thermostat and see if that brings it to life...and go from there

[wavery]

well I will check it out again at San Clemente and then hot wire the thermostat and see if that brings it to life...and go from there

Re-read the previous post.....I added some stuff, including a manual.

[coach]

scroll down!!!

[coach]

I always thought the sail switch needed to close (enough air flow) before the direct spark ignition would spark.
The gas valve needs the sail switch to close and the little on/off red rocker switch (if equipped) on the front of the furnace - behind the grill.
Some folks report a 'reset' button in lieu of an on/off switch, others neither.

Page 16 sequence of operation

[wavery]

I always thought the sail switch needed to close (enough air flow) before the direct spark ignition would spark.
The gas valve needs the sail switch to close and the little on/off red rocker switch (if equipped) on the front of the furnace - behind the grill.
Some folks report a 'reset' button in lieu of an on/off switch, others neither.

Page 16 sequence of operation

:book: Good catch Coach......so, if the fan is blowing and the igniter is clicking, the sail switch is OK.....

How ya doin' :sombraro:there Dieter?

[dkutz]

OK well I meesed witht he heater before I packed up this morning.  Got it to run again after cleaning hte contacts int he thermostat.  The fan turned on, and the ignitor clicked three times, and then it all stopped.  The red light blinking three times means, "ignition sequence problem" or something like I that, I wrote it down.  I didn't have time to start tearing things apart....  SO maybe bad ignitor?  OR bad fuel dilivery.  SOmeday I will figure it out.

[wavery]

OK well I meesed witht he heater before I packed up this morning.  Got it to run again after cleaning hte contacts int he thermostat.  The fan turned on, and the ignitor clicked three times, and then it all stopped.  The red light blinking three times means, "ignition sequence problem" or something like I that, I wrote it down.  I didn't have time to start tearing things apart....  SO maybe bad ignitor?  OR bad fuel dilivery.  SOmeday I will figure it out.

If you hear the ignitor clicking....it's working. The sound that you hear is the actual electric arching.

That leaves the gas valve, blocked gas line or the circuit board (if it were the sail switch, the ignitor wouldn't "click", as Coach pointed out.... ).

I would turn on the propane and slowly loosen the main gas feed into the gas valve. If you hear a hissing sound, tighten the nut back up. If you don't get any gas escaping with the nut all the way loose, turn off the propane tank. Follow that gas line back to where it connects to the main gas line. Disconnect the pipe there, turn on the propane to see if you have any at that point. Keep working your way back until you find the blockage (keep a fan going in the trailer and don't light any matches when checking for gas). Then blow compressed air through the pipe until it is clear.

If you did get hissing at the gas valve, you have a problem at the valve. Check to see if it is getting the proper voltage when the fan kicks on. If it does, the solenoid is stuck. If it doesn't, you could have a bad wire or bad ground. You could also have a bad circuit board. Check the voltage at the board.

The bottom line is, you need fuel and spark. You have spark so that means you are not getting fuel. Find out why.......and quit making me write all this stuff.......you don't read it anyway....:banghead:

[dkutz]

If you hear the ignitor clicking....it's working. The sound that you hear is the actual electric arching.
 
That leaves the gas valve, blocked gas line or the circuit board (if it were the sail switch, the ignitor wouldn't "click", as Coach pointed out.... ).
 
I would turn on the propane and slowly loosen the main gas feed into the gas valve. If you hear a hissing sound, tighten the nut back up. If you don't get any gas escaping with the nut all the way loose, turn off the propane tank. Follow that gas line back to where it connects to the main gas line. Disconnect the pipe there, turn on the propane to see if you have any at that point. Keep working your way back until you find the blockage (keep a fan going in the trailer and don't light any matches when checking for gas). Then blow compressed air through the pipe until it is clear.
 
If you did get hissing at the gas valve, you have a problem at the valve. Check to see if it is getting the proper voltage when the fan kicks on. If it does, the solenoid is stuck. If it doesn't, you could have a bad wire or bad ground. You could also have a bad circuit board. Check the voltage at the board.
 
The bottom line is, you need fuel and spark. You have spark so that means you are not getting fuel. Find out why.......and quit making me write all this stuff.......you don't read it anyway....:banghead:

Oh I read it I just don't have time to trouble shoot all this stuff, nor did I have the proper tools with me...I will check the gas line next...