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Topic: Need Help with 93, U300 Gas Furnace (Read 1115 times) previous topic - next topic

Need Help with 93, U300 Gas Furnace

I just tried my front Gas Furnace for the first time last night. No Go.

This morning when I turned it on the blower started as usual and then the electronic igniter started a flame for maybe 2 seconds but the flame immediately went out. I pulled all of the electrical connections apart and cleaned them and used electronics cleaner on the connections. Still the gas flame goes out immediately after ignition. It appears that the thermocouple is shutting off the gas as soon as it first lights. I have heard of insects getting up into the system but I can see no obstructions in the flu pipe. Where else should I check?

HELP! Its supposed to get cold again tonight. 
The selected media item is not currently available.Kent Speers
Locust Grove, OK
1993 U300 SSE 40' (Restored at FOT 2009) Build 4323
720 watts Solar
6V92TA DDEC Silver Engine
2014 Subaru Outback

Re: Need Help with 93, U300 Gas Furnace

Reply #1 –
Quote
I just tried my front Gas Furnace for the first time last night. No Go.
This morning when I turned it on the blower started as usual and then the electronic igniter started a flame for maybe 2 seconds but the flame immediately went out.
Here are some furnace troubleshooting resources
http://www.marksrv.com/furnace_trouble_shooting.htm
http://www.rvmechanic.com/current_category.181/Forum.21957/offset.1290/forum_thread_full.html
http://www.rverscorner.com/articles/furnace1.html
http://www.beamalarm.com/foretravel-links/foretravel-technical-help.htm#Furnace

Here is a previous thread that might help
http://www.foreforums.com/index.php?topic=10475.msg49793#msg49793

The selected media item is not currently available.Barry BEAM #16014
2003 U320 40' AGDS
Beamalarm, Foretravel technical help and specifications
"Whatever the mind can conceive and believe, it can achieve"

Re: Need Help with 93, U300 Gas Furnace

Reply #2 –
Thanks Barry. I followed and participated in the August thread. The difference here is that the burner ignites for a few seconds. From the other threads you supplied it appears the problem could be the limit switch, the circuit board or a venting problem. I will keep working on it but if someone has had the same problem and found the fix, I would really appreciate help. I really don't want to disassemble the entire furnace if I don't have to.
The selected media item is not currently available.Kent Speers
Locust Grove, OK
1993 U300 SSE 40' (Restored at FOT 2009) Build 4323
720 watts Solar
6V92TA DDEC Silver Engine
2014 Subaru Outback

Re: Need Help with 93, U300 Gas Furnace

Reply #3 –
The first time I had a similar problem the manager of a RV park in Angel Fire, New Mexico showed me a very technical (he said) repair.  He hit the outside cover of the furnace with the side of his fist.  This caused the sail switch to free up and the furnace to light.  The sail switch gets a lot of dust.  I have used this method once or twice since then.  This may not solve your problem, but it is worth a try.  This man said I may have to access the sail switch to blow it off some time, but that has never been necessary.
I have passed this information on to a couple of people since then, and it worked. 
Good luck,
Alan Dodson
1991 GV 280
Alan Dodson
1991 U280 GV 36'

Re: Need Help with 93, U300 Gas Furnace

Reply #4 –
Alan, thanks for your input. I always called the repair you described a "Factory Adjustment", either a good wallop or if its portable a 2" drop. Naturally that was my first inclination. I have walloped, tapped and even considered clobbering the valve and thermocouple to no avail.

However, I am curious about the Sail Switch you mentioned. I am not familiar with that term. Where is it located? I think it is probably something very simple like that but I have tapped and wiggled everything I can see that I think could have sticking parts. All advice is appreciated.
The selected media item is not currently available.Kent Speers
Locust Grove, OK
1993 U300 SSE 40' (Restored at FOT 2009) Build 4323
720 watts Solar
6V92TA DDEC Silver Engine
2014 Subaru Outback

Re: Need Help with 93, U300 Gas Furnace

Reply #6 –
Peter, I checked the link and saw a photo of the Sail Switch. My unit has a Hydro-Flame Furnace and I don't see anything that looks like that on my unit. Is it hidden somewhere? Do you know what the function is that might lead me to finding it?

By the way, I trust things are better in Arkansas. We have been dealing with some family health issues as well. I know how stressful that can be.
The selected media item is not currently available.Kent Speers
Locust Grove, OK
1993 U300 SSE 40' (Restored at FOT 2009) Build 4323
720 watts Solar
6V92TA DDEC Silver Engine
2014 Subaru Outback

Re: Need Help with 93, U300 Gas Furnace

Reply #7 –
Kent,
Frankly, I just Googled the term and various options came up.  The link below gives a bit more explanation as to its function.
 
http://www.rverscorner.com/articles/furnace1.html#sail
 
And, thanks for the kind thoughts.  Family health issues are always stressful, thankfully all went well during the procedure and Susan is a champ.  I hope your situation has a good outcome as well.
Peter & Beth Martin
No Forrest? What have you done?
MC# 15890 until Dec 2016; FMCA #F329677
Cincinnati, OH

Re: Need Help with 93, U300 Gas Furnace

Reply #8 –
I had searched the Internet pretty thoroughly before posting so I had already seen most of these links. I had just hoped that someone had previously had the same experience. Its pretty unusual for the flame to light and then go back out immediately. I thought that would have a specific and identifiable cause.
The selected media item is not currently available.Kent Speers
Locust Grove, OK
1993 U300 SSE 40' (Restored at FOT 2009) Build 4323
720 watts Solar
6V92TA DDEC Silver Engine
2014 Subaru Outback

Re: Need Help with 93, U300 Gas Furnace

Reply #9 –
If the gas valve is opening/igniter sparking, the sail switch is OK (as is air flow).  If the sail switch doesn't see adequate air flow, neither gas valve nor igniter will function.

I don't have my manuals with me (we are out of the country in the BVI right now), but see if there is a thermocouple.  A thermocouple's job is to confirm flame/heat and let the PC board know that it is OK to continue to keep the gas valve open.

Brett Wolfe
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Need Help with 93, U300 Gas Furnace

Reply #10 –
A thermocouple was my best guess but I can't see an easy way to get to it. I'm pretty handy but I hate tearing into an RV furnace. Unless someone comes up with something simple, I guess I will have to take it to an RV Repair Shop. Man I hate paying people to do what I probably can do myself better, but a minor mistake on a furnace is not something I want to risk.

Come on, someone out there must have had this problem. HELP!
The selected media item is not currently available.Kent Speers
Locust Grove, OK
1993 U300 SSE 40' (Restored at FOT 2009) Build 4323
720 watts Solar
6V92TA DDEC Silver Engine
2014 Subaru Outback

Re: Need Help with 93, U300 Gas Furnace

Reply #11 –
Kent,
 
Don't overlook the Escapees Forum.  Lots of furnaces out there. 
George Stoltz.  Retired from full-time living in a great Foretravel and now are back to living in a traditional sticks and bricks in Florida.

Re: Need Help with 93, U300 Gas Furnace

Reply #12 –
Kent,
Did you ever solve this?  I'm curious because I was just checking the operation of mine and I'm now having the same problem.  I removed the circuit board and found a lot of condensation around it.  I baked the board in the oven (125 F) and let it sit out in the sun.  Upon re-installation had same symptoms (ignition for only 2-3 seconds).  I then swapped out the circuit boards between the front and rear furnaces.  Both furnaces worked.  I swapped the boards back again.  Same problem on the original furnace.  One thing I should mention is that the 2nd (good) furnace has a Dinasour "FAN 50 PLUS" board on it that I changed out 5+ years ago.  I don't remember the symptoms but I did determine the board was bad by swapping out the boards.  My guess now is the board is on the edge of it's ability to detecting the flame and the other furnace has maybe cleaner electrodes that give it a slightly better signal.  I'm interested to hear what you discovered.
John Fitzgerald
1991 U300 (SAI) Side Aisle Island Bed 40'
Detroit 6V92 with Allison Retarder
Meridian (Boise), Idaho

Re: Need Help with 93, U300 Gas Furnace

Reply #13 –
Quote from: JohnFitz –
Kent,
Did you ever solve this?  I'm curious because I was just checking the operation of mine and I'm now having the same problem.  I removed the circuit board and found a lot of condensation around it.  I baked the board in the oven (125 F) and let it sit out in the sun.  Upon re-installation had same symptoms (ignition for only 2-3 seconds).  I then swapped out the circuit boards between the front and rear furnaces.  Both furnaces worked.  I swapped the boards back again.  Same problem on the original furnace.  One thing I should mention is that the 2nd (good) furnace has a Dinasour "FAN 50 PLUS" board on it that I changed out 5+ years ago.  I don't remember the symptoms but I did determine the board was bad by swapping out the boards.  My guess now is the board is on the edge of it's ability to detecting the flame and the other furnace has maybe cleaner electrodes that give it a slightly better signal.  I'm interested to hear what you discovered.

John, I checked my board by using it in the rear furnace successfully. I then replaced the sensing unit/thermocouple/piezo unit. Nothing seemed to work. I finally took it to an Atwood technician. He found that the propane regulator on the propane tank was going bad. There was not enough pressure to  keep the furnace going. After replacing the regulator, $29.95, the furnace works great. I still don't understand why the rear furnace and the stove top worked when the front furnace didn't. The Atwood tech told me there are two regulators. If so, I don't know where the second one is. 
The selected media item is not currently available.Kent Speers
Locust Grove, OK
1993 U300 SSE 40' (Restored at FOT 2009) Build 4323
720 watts Solar
6V92TA DDEC Silver Engine
2014 Subaru Outback
 

Re: Need Help with 93, U300 Gas Furnace

Reply #14 –
Kent,

Check the BTU rating of the two furnaces. It is quite possible that a failing propane regulator could supply enough gas to power a lower BTU unit, but not the higher BTU unit. Likewise, the stove takes quite a lot less gas to run.

Brett
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020