Furnace Pilot goes out when burner lights

[scissortech]

Sent: 9/6/2004 5:10 PM

My 78 Brave has a Coleman furnace.  I just replaced the blower (burned out)because the burner will not lite without the sail switch.  Now I have a new problem--My pilot lite goes out when the main burner comes on!  Within seconds it all shuts off.  The pilot lite is up as far as I can get it (which isn't saying much) and I've adjusted the gas pressure to get a higher pilot (didn't work).  The pilot does stay lit if the furnace doesn't try to lite the main burner.

Anybody got any other ideas?
Bob

[salplmb]

Sent: 9/6/2004 7:53 PM

i would check to see if the orifice for the pilot is blocked somehow. if the pilot goes out when the burner lites it sounds like there is a low pressure situation. i know its kind of hard to get into but if you can get the burner to lite and then try to lite pilot again, if you cant get the pilot to stay lit while the burner is going then something is wrong with the gas valve. if you tried to adj. the pilot flame and the adj. made no difference it sounds like the pilot is somehow blocked. hope this helps a little
sal

[scissortech]

Sent: 9/11/2004 2:14 PM

Thanks for the suggestion Sal.  I thought of another thing that could also cause that.  If the air intake is plugged, the oxygen would get used up and put it all out also.  I'll check them both out.

Bob

[Cooneytoones]

Sent: 9/12/2004 10:35 PM

If those other fixes don't work. First check for spiders, they love the pilot hole area. You can clean out the pilot tube gently with a pipe cleaner (from a tobacco store)......If that doesn't work then.......
Sounds like it may be in the valve itself. It could be a simple as a piece of dirt. There is now way to put a drip leg on an RV furnace. A drip leg is used to capture any small piece of debris that might get in the LP Gas line. If a small piece is in there, with just on pilot, the pilot will work OK...then the thermostat calls for heat the valve opens, gas comes through bigger line at a higher pressure, and our little piece of dirt gets forced into little 1/4 pilot line and blocks the gas to pilot. That what this sounds like. Worst it could be is a bad valve, very replaceable. But try this first. Take valve off furnace and blow out (not with hurricane force wind) gently blow out valve with an air hose. Also blow out all appliance lines, Shut off tank(s) disconnect all  LP lines where they enter the appliance, remove LP line on Coach side of regulator, blow out.  This you can use hurricane force winds for...Re tighten all connection, and check for leaks (not with a match, as I've seen some people do.) Use Soapy water. .....Hope this helps......Keep warm.
, that last fix is if furnace is running OK. But after reading your post again, You did say, that the whole kit-an-kobble shuts down pretty quick after burners light? Correct? Then you have a dirty cad cell,  Little sensor that sees a flame. Look for a small white glassy looking cap near the burner, kind of like an eclectic eye. That is a flame sensor, clean it off real good and make sure nothing is blocking it. If it does not a see flame, it will shut down the whole system including pilot.

From: cooneytunes   
Sent: 9/12/2004 10:35 PM

If those other fixes don't work. First check for spiders, they love the pilot hole area. You can clean out the pilot tube gently with a pipe cleaner (from a tobacco store)......If that doesn't work then.......
Sounds like it may be in the valve itself. It could be a simple as a piece of dirt. There is now way to put a drip leg on an RV furnace. A drip leg is used to capture any small piece of debris that might get in the LP Gas line. If a small piece is in there, with just on pilot, the pilot will work OK...then the thermostat calls for heat the valve opens, gas comes through bigger line at a higher pressure, and our little piece of dirt gets forced into little 1/4 pilot line and blocks the gas to pilot. That what this sounds like. Worst it could be is a bad valve, very replaceable. But try this first. Take valve off furnace and blow out (not with hurricane force wind) gently blow out valve with an air hose. Also blow out all appliance lines, Shut off tank(s) disconnect all  LP lines where they enter the appliance, remove LP line on Coach side of regulator, blow out.  This you can use hurricane force winds for...Re tighten all connection, and check for leaks (not with a match, as I've seen some people do.) Use Soapy water. .....Hope this helps......Keep warm.

That last fix is if furnace is running OK. But after reading your post again, You did say, that the whole kit-an-kobble shuts down pretty quick after burners light? Correct? Then you have a dirty cad cell,  Little sensor that sees a flame. Look for a small white glassy looking cap near the burner, kind of like an eclectic eye. That is a flame sensor, clean it off real good and make sure nothing is blocking it. If it does not a see flame, it will shut down the whole system including pilot.
Timmy

[scissortech]

Sent: 9/19/2004 5:16 PM

Thanks for your feedback.  It's great to know there are people, like myself, that have been there and done that.

Bob