[GMCnet] Furnace problems [message #40676] |
Fri, 17 April 2009 12:56 |
kenneth hugelier
Messages: 89 Registered: August 2008
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This problem is starting to get on my nerves. I'm hoping for a little help here. My 30K btu Suburban furnace which, according to the records I got from the PO, was replaced in the mid-nineties, does not work according to "hoil". When I set the thermostat and turn the switch on, the furnace fires up after the correct wait time and the fan starts and it produces heat for about 3 to 4 minutes. The flame then goes out and (with a new "Dinasaur" ignition board) tries to start three times then shuts off. I replaced the ignition board (see above). I called Dinasaur and was talked through some simple checks using a VOM. The high tension ignition wire is good the coil on the new board is good, the jumper is removed. Dinasaur sent me a new board (second one) and I got the same results. I checked the gas pressure with a water column and it is set at 10 inches. I jumped out the thermostat to no avail. The only thing left is the gas valve, but before I spend
more money, I thought I would try to get some help here. Help anyone?
ken hugelier
77 PB
Det. Mich.
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Re: [GMCnet] Furnace problems [message #40679 is a reply to message #40676] |
Fri, 17 April 2009 13:23 |
storm'n
Messages: 492 Registered: April 2007 Location: Ont. Can
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Sounds like the hi-temp safety switch is kicking it out. Put a jumper across & see if it still kicks out. Don't leave it unattended this way. Have you got good hot air circulation?
--- On Fri, 4/17/09, ken hugelier <kahugelier@sbcglobal.net> wrote:
From: ken hugelier <kahugelier@sbcglobal.net>
Subject: [GMCnet] Furnace problems
To: gmclist@temp.gmcnet.org
Received: Friday, April 17, 2009, 1:56 PM
This problem is starting to get on my nerves. I'm hoping for a little help here. My 30K btu Suburban furnace which, according to the records I got from the PO, was replaced in the mid-nineties, does not work according to "hoil". When I set the thermostat and turn the switch on, the furnace fires up after the correct wait time and the fan starts and it produces heat for about 3 to 4 minutes. The flame then goes out and (with a new "Dinasaur" ignition board) tries to start three times then shuts off. I replaced the ignition board (see above). I called Dinasaur and was talked through some simple checks using a VOM. The high tension ignition wire is good the coil on the new board is good, the jumper is removed. Dinasaur sent me a new board (second one) and I got the same results. I checked the gas pressure with a water column and it is set at 10 inches. I jumped out the thermostat to no avail. The only thing left is the gas valve, but before I spend
more money, I thought I would try to get some help here. Help anyone?
ken hugelier
77 PB
Det. Mich.
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Re: [GMCnet] Furnace problems [message #40683 is a reply to message #40679] |
Fri, 17 April 2009 13:44 |
idrob
Messages: 645 Registered: January 2005 Location: Central Idaho
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storm'n wrote on Fri, 17 April 2009 11:23 | Sounds like the hi-temp safety switch is kicking it out. Put a jumper across & see if it still kicks out. Don't leave it unattended this way. Have you got good hot air circulation?
--- On Fri, 4/17/09, ken hugelier <kahugelier@sbcglobal.net> wrote:
From: ken hugelier <kahugelier@sbcglobal.net>
Subject: [GMCnet] Furnace problems
To: gmclist@temp.gmcnet.org
Received: Friday, April 17, 2009, 1:56 PM
This problem is starting to get on my nerves. I'm hoping for a little help here. My 30K btu Suburban furnace which, according to the records I got from the PO, was replaced in the mid-nineties, does not work according to "hoil". When I set the thermostat and turn the switch on, the furnace fires up after the correct wait time and the fan starts and it produces heat for about 3 to 4 minutes.
(snip)
The only thing left is the gas valve, but before I spend
more money, I thought I would try to get some help here. Help anyone?
ken hugelier
77 PB
Det. Mich.
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The high temp switch is very suspect, as was mentioned above. Bridge it and try another attempt to see if it stays on. They are a normally closed bi metalic snap switch, and when they get tired, they conduct when they want and then with heat the spring pressure is not enough to keep the contacts closed. The other thing is the fan sail switch, which may be dropping out if the fan slows down after running a little. That can happen due to either low voltage, or just a tired fan. More common for them to start slow and speed up, but I have seen it happen that they slow down with time too. I also had a sail switch that was just bent enough so it was erratic in operation. I bent it back to original, and it was then fine.
I'll bet on the high temp switch though.
Rob Allen
former owner of '76 x-PB
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Re: [GMCnet] Furnace Problems [message #40715 is a reply to message #40706] |
Fri, 17 April 2009 19:50 |
roy1
Messages: 2126 Registered: July 2004 Location: Minden nevada
Karma: 6
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Ken
Did you put a voltmeter across the coil of the gas valve when it is trying to start( the spark will be clicking at this time).
If there is power to the valve at this time and you can see the spark is good the flapper in the valve is possibly stuck closed. Another possibility is the burner rack may need to be cleaned.
Roy
Roy Keen
Minden,NV
76 X Glenbrook
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Re: [GMCnet] Furnace problems [message #40734 is a reply to message #40676] |
Fri, 17 April 2009 23:11 |
whmckinley
Messages: 13 Registered: March 2008 Location: Mayfield Village
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Have you checked the fly switch (I think that was what it was called) , Mine had a switch that would be closed when the fan was up to speed. If it didn't blow enough air, IE: inlet blocked, dirty squirrel cage, flakey blower motor, the air paddle inside the outlet chamber wouldn't move enough to close the switch. It would shut down after 3 minutes. Mine was caused by a flakey blower motor, pulled it apart, cleaned and oiled it. Didn't have the problem afterward. That was on my previous SOB. Putting a new furnace in my GMC during the rebuild.
Bill
1973 Glacier
26ft bowling alley with wheels
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Re: [GMCnet] Furnace problems [message #40786 is a reply to message #40734] |
Sat, 18 April 2009 13:12 |
emerystora
Messages: 4442 Registered: January 2004
Karma: 13
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On Apr 17, 2009, at 10:11 PM, william mckinley wrote:
>
>
> Have you checked the fly switch (I think that was what it was
> called) , Mine had a switch that would be closed when the fan was up
> to speed. If it didn't blow enough air, IE: inlet blocked, dirty
> squirrel cage, flakey blower motor, the air paddle inside the outlet
> chamber wouldn't move enough to close the switch. It would shut down
> after 3 minutes. Mine was caused by a flakey blower motor, pulled it
> apart, cleaned and oiled it. Didn't have the problem afterward. That
> was on my previous SOB. Putting a new furnace in my GMC during the
> rebuild.
> --
> Bill
> 1973 Glacier
> 26ft bowling alley with wheels
>
That is called a "sail" switch. I was just going to suggest that when
I read your message.
Emery Stora
77 Kingsley
Santa Fe, NM
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Re: [GMCnet] Furnace problems [message #41027 is a reply to message #41026] |
Tue, 21 April 2009 08:34 |
C Boyd
Messages: 2629 Registered: April 2006
Karma: 18
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kenneth hugelier wrote on Tue, 21 April 2009 09:24 | I have an NT 30. The parts list shows a limit switch and a paddle switch and a relay. I'm leaning toward the limit switch as being the source of my problem. Thanks.
ken hugelier
77 PB
Det. Mich.
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Sir: This may not be your issue, bit I had a house unit that would fire up, run a little and shut down. Turned out the burner box had a hole in it and was allowing fire and too much heat to the vents. High limit was kicking for a reason..
C. Boyd
76 Crestmont
East Tennessee
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Re: [GMCnet] Furnace problems [message #41048 is a reply to message #41047] |
Tue, 21 April 2009 11:22 |
C Boyd
Messages: 2629 Registered: April 2006
Karma: 18
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kenneth hugelier wrote on Tue, 21 April 2009 11:59 | Thanks for the reply. I have a plug-in CO detector in the house. I can plug it in to the coach while it's in the drive on shore power and fire up the furnace and maybe see if I have a combustion chamber leak. Hope not, because that means new furnace time.
ken hugelier
77 PB
Det. Mich.
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Ken: In my case I also have a pulg in detector but being the idiot I am, I had it plugged in close to the return air filter instead of closest to the burner in the bedroom. So the detector did not work in my case.. I was fortunate the high limit did its job..
C. Boyd
76 Crestmont
East Tennessee
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Re: [GMCnet] Furnace problems [message #41106 is a reply to message #41026] |
Tue, 21 April 2009 18:35 |
fred v
Messages: 999 Registered: April 2006 Location: pensacola, fl.
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kenneth hugelier wrote on Tue, 21 April 2009 08:24 | I have an NT 30. The parts list shows a limit switch and a paddle switch and a relay. I'm leaning toward the limit switch as being the source of my problem. Thanks.
ken hugelier
77 PB
Det. Mich.
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don't just throw money at a problem. find the problem. did you download the manual? it has a great diagnostic section.
Fred V
'77 Royale RB 455
P'cola, Fl
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Re: [GMCnet] Furnace Problems [message #41147 is a reply to message #41127] |
Wed, 22 April 2009 07:20 |
fred v
Messages: 999 Registered: April 2006 Location: pensacola, fl.
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kenneth hugelier wrote on Tue, 21 April 2009 21:37 | Fred,
If you mention the site where I can download and print the diagnostic part of the manual, it would save me a lot of time. Thanks.
ken hugelier
77 PB
Det. Mich.
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http://bdub.net/manuals/index.html
lots of good stuff here.
Fred V
'77 Royale RB 455
P'cola, Fl
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