Furnace ignition

[PAkev]

We have a mobile home that is used a few weeks throughout the year at our hunting camp. It is heated by a LP gas Coleman/Evcon furnace. However, we can not seem to get the furnace going this year as it is exhibiting the following problems: The thermostat will signal the furnace to turn on, the ignition element will glow, the valve will open to allow gas into the combustion chamber, but the furnace will not ignite. <br /><br />So far, I have changed the LP control valve, 12/24 Volt transformer and a module box without any results.<br /><br />Could the ignition heater element be bad even though it is getting power and getting hot?<br /><br />Helpful Thoughts Appreciated.

 

[Rick Byers]

Re: Furnace ignition

Does the blower start up at a slow speed when the Igniter starts glowing if not it won't ever light off there is an interupter in the circuit to stop ignition if the blower doesn't start up.

 

[datawire]

Re: Furnace ignition

I assume the LP source has sufficent gas in it... but it really sounds like it's not getting to your unit. Can you smell LP when the valve opens? Have you cycled it enough times to purge the air from the lines? Have you tried to ignite it (very carefully) with a long match in one hand and the power cord in the other (so you can jerk it loose if need be)? Check for blue flakey stuff on the inlet screen of the Main Gas Valve. The next steps will require a gas pressure gauge.<br />Hope this helps.

 

[Mark42]

Re: Furnace ignition

Common problem with gas furnaces that are not used frequently: Spider webs. Remove and clean the burner unit and try again. It may be the problem.

 

[PAkev]

Re: Furnace ignition

Thanks for the reply's ....<br /><br />The tank is about 50% full and the control valve is getting about 12lbs pressure. The primary blower is kicking on OK when the thermostat engages the furnace, the main blower activates once the heat chamber reaches temperature. (unfortunately, were not there yet) Everything electrical seems to be doing what it supposed to be doing.<br /><br />My next thought is to look for a plugged orface or a faulty ignition element. <br /><br />Although the ignition element is glowing and is obviously hot, it there a way to tell if it may be weak due to aged condition ?<br /><br />Thanks!<br />Kevin

 

[Xcusme]

Re: Furnace ignition

Hey PAkev,<br /><br />What's the model number of your furnace??<br /><br />Edit:<br /><br />You may have REALLY BIG PROBLEMS!!<br /><br />Read This ASAP !!!<br /><br /> Warning- Recall

 

[SS MAYFLOAT]

Re: Furnace ignition

Xcusme Those are units that have faulty Hi-limit switchs.<br /><br />PAkev, sounds to me like the sensor that verifys the heat from your hot surface ignitor is malfunctioning. In order for the gas valve to open, it has to get a signal that there is in fact a hot surface from your ignitor. It is similar to a thremalpyle or thermalcouple for a regular pilot light. SOme of the hot surface style ignitors use a optical sensor that senses the brightness of the ignitor.<br /><br />I think this could be your problem. It is one of the most common.. Good Luck.. BTW, the sensors are not that expensive.<br /><br />Might want to check what gas pressure the furnace is required to have. 15 pounds sounds like a bit much to me. However I don't deal with LP, just mostly gas and it is around a pound and a half pressure.<br /><br />Most definetly make sure your unit is not on a recall, if it is, get in touch with your authorized agent. <br /><br />Again, good luck and be VERY VERY Careful!

 

[Xcusme]

Re: Furnace ignition

SS MAYFLOAT:<br />In the first part of my last post, I asked about the model number of his furnace to see if he fell under the recall. After not getting a timely response, I edited with the link to the recall. I certainly didn't want to come off as an alarmist, but only to make him aware of the potential fire hazard, despite the non-ignition issue.<br /><br />You're probably right, either the hot surface ignitor or the sensor has gone South. It's probably going to turn out to be a spider nest blocking the gas jet or some other otherwise simple fix.

 

[PAkev]

Re: Furnace ignition

Thanks Guys,<br /><br />I had a furnace guy go and look at it today. He called and talked to my wife indicating he did some trouble shooting and got it working. Not sure what he did until I get his bill. I will post the problem to bring you guys up to speed after I talk to him.<br /><br />The furnace is older than the ones on recall from 1995 through 2000. I think it is early 90's. However, I am going to double check the model # when I go there this weekend just to be sure.<br /><br />Kevin

 

[Snookster]

Re: Furnace ignition

I bet you'll find the tech had to clean the contacts on the inducer blower. These contacts are in series with the gas valve & prove air is moveing in the combustion chamber B4 the valve will open. It's common in RV's for moisture to have these contacts stuck or even welded (they're on the end of the blower shaft). If it happens again, clean them with electrical contact cleaner - if they continue to hang up - replace.

 

[Ben Konopacky]

Re: Furnace ignition

I have seen it many a time !!! main gas valve was shut off. just a taught.

 

[dogsdad]

Re: Furnace ignition

I don't know much about the subject, but I once had problems keeping the pilot going in a mobile home heater. After relighting it a number of times, it finally went "KAAAABOOOOOOOM!" Scared the hell outa my dogs! Didn't do much to calm my nerves either!<br /><br /><br />-dd-