| [GMCnet] Help. 30 degress out with snow. Furnace not lighting. [message #275553] |
Fri, 10 April 2015 09:18 |
glwgmc
Messages: 1014
Registered: June 2004
Karma:
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Senior Member |
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CORRECTION
The easy access between the furnace and refrigerator 12vdc is on the Royale, not on the stock GMC configuration. Sorry for the confusion.
Jerry
Jerry Work
The Dovetail Joint
Fine furniture designed and hand crafted in the 1907 former Masonic Temple building in historic Kerby, OR
glwork@mac.com
http://jerrywork.com
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Message: 7
Date: Thu, 09 Apr 2015 18:58:41 -0700
From: Gerald Work
To: Gmc Forum
Subject: [GMCnet] Help. 30 degress out with snow. Furnace not
lighting.
Message-ID:
Content-Type: text/plain; charset=us-ascii
Hi Bob,
With those symptoms it likely is low voltage at the furnace or a bad ground at the furnace or your thermostat is bad. It sounds like both boards worked for a while so likely neither bad. Pull the connector on the side of the furnace. On the V side will be two wires in the first hole (battery + and feed to the thermostat), then a ground, then the return from the thermostat. The battery + and feed to the thermostat should be very close to what you measure for voltage at your house battery. No more than a few tenths of a volt drop when measured against the ground wire at that connector. With the thermostat on and calling for heat you should measure that same voltage or very close to it on the line coming from the thermostat. The thermostat is just an on/off switch. That voltage passes through the sail switch (to make sure the fan is running at the correct speed for good ignition) and the high limit switch (to make sure the furnace is not already over temp) and returns to
the board to tell it to open the propane valve and ignite. I find these furnaces quite sensitive to lower voltages than they expect so sometimes the board will see the lower than normal voltage as a sign that something is wrong and it shuts down. If voltage is lower than house battery voltage, then check the master ground on the house fuse box. If yours is a GMC finished coach but you are seeing low voltage at the furnace, then you can often find good voltage at the refrigerator 12vdc junction which will be just one thin wooden wall removed from the compartment under the sink where the furnace is located. Use 12ga wire from the furnace to that junction for both positive and ground to the furnace.
Jerry
Jerry Work
The Dovetail Joint
Fine furniture designed and hand crafted in the 1907 former Masonic Temple building in historic Kerby, OR
glwork@mac.com
http://jerrywork.com
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Message: 14
Date: Thu, 9 Apr 2015 20:18:25 -0500
From: Bob Dunahugh
To: "gmclist@temp.gmcnet.org"
Subject: [GMCnet] Help. 30 degress out with snow. Furnace not
lighting.
Message-ID:
Content-Type: text/plain; charset="iso-8859-1"
Has new sail switch. Put in new board in Dec. Worked fine in Patterson. Unit quit 2 days ago in Missouri. Put back in old board. Worked fine till 2 hours ago here in Minnesota. Going home to Iowa in 4 days. Can someone that knows these well call me. Cold Bob Dunahugh up North again. 319-521-4891
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Jerry & Sharon Work
78 Royale
Kerby, OR
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