Coleman Furnace works when it feels like it?

[northfork13]

Sent: 9/25/2008

In 1979 Minnie Winnie 20 ft .The furnace runs great on start up.then when  your sound asleep and about 4 am it decides to blow only cold air , it will continue to blow cold air until it is shut off via the thermostat and restarted? There is no continual clicking like it trying to restart , just the blower and cold air. Any ideas? I've been told "sail flap" but don't know where to look for it or even what it looks like?
Help please,

Northfork13

[denisondc]

Sent: 9/25/2008

The sail-switch function is to ensure there is air blowing, before the main burner is turned on. That 'sail' would be a metal plate connected to a switch, and would be inside the plenum of the furnace. To check mine, (which was sticking) I had to pull the furnace out of its position, into the interior of the RV. Then I had to take lots of screws out to be able to slide the innards of the furnace out of the main housing. The sail-switch was sticking because a large mouse-nest was in place.

[ClydesdaleKevin]

Sent: 9/30/2008

Mine is all messed up too...was working fine, and now, while the pilot lights right up, the furnace itself won't fire up, so the blower won't work either.  I'm going to clean it all up, which means pulling it and partially disassembling it, make sure the temp bulb is over the pilot, and then see if it works.  If it doesn't, I'm gonna go with a new one...probably an Atwood, 20K BTU, which is the size this old Coleman is.

Kev

[HAL]

Sent: 9/30/2008

  If the pilot lights, but the burner will not it is probe the thermocouple not sensing the heat. from the pilot. You can clean the thermocouple with fin steel wool or 400 sand paper.


Hal

[Slantsixness]

Sent: 10/1/2008

Northfork,

Sail switch is a good possibility, if it's sticking..... which it sound like its getting stuck when hot...

But... it could be the igniter board... you mention "no Clicking on restart"... which sounds to me like a couple of things:

(the pretense here is that you have a heater with electronic igniter, and no pilot light)

1. igniter wire is loose, or improperly aligned with the gas jet, so it only ignites "sometimes". this could be from a frayed or corroded igniter, or corroded igniter wire. usually you can cut the wire back a little (no more than an inch or it'll be too short!) and reinstall it if it's the wire, or clean the igniter rod itself with steel wool and all will work again

2. igniter board bad, or intermittent. Check the connections to the board, which include the connection to the sail switch.. that'll kill it too.

3. Gas solenoid intermittent (but you would hear it clicking, trying to ignite, but no gas so this is not likely)

3. if the heater is new enough, it can shut down and not ignite because of a blocked inlet and outlet vent (outside the rig) Newer heaters have two "sail" switches, one in the impeller/ evacuator side (outside vents), and one in the Blower (inside heat vents)

since I don't know which heater you actually have (sounds like a suburban though...) so this is kind of a generic answer...

[bluebird]

Sent: 10/7/2008

On the Coleman, you can remove the front panel. There is a small window on the lower left side. Turn the stat to heat, and see if you see a spark or pilot light. If there is no spark, it is in the sail switch or the board. The sail switch will pass 12vdc to the board if working. If the pilot lites but the main burner don't, then the flame sensor or the flame sensor part of the board is bad. I've been told this is a common problem with them. I replaced the board on my old Itasca a few years ago with a dinosaur board. It worked perfect. I think it ran around 60.00 for the new board. It is much easier to remove the furnace to replace the board, but it can be done in place if you are young and flexible. I couldn't !!

[northfork13]

Sent: 10/15/2008

Wow so much info, Thanks to all of you! We will try out the suggestions given and keep you posted on our progress.

[northfork13]

Well sorry about the delay in response to your help.... we vacumed out around the furance and found a old magazine had dropped down from the cupboard above and blocked the air flow...
Problem solved with a little maintance LOL .Thanks again for all your help.