| [GMCnet] Help. 30 degrees out with snow. Furnace not lighting. [message #275568] |
Fri, 10 April 2015 12:07 |
glwgmc
Messages: 1014
Registered: June 2004
Karma: 10
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Senior Member |
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Hi Bob,
The only difference you should see in voltage between the volts at the battery and at the furnace would be due to resistance in the wire or resistance at connections or resistance at grounds, a few tenths of a volt at most. Unplug the connector on the forward side of the furnace (squeeze clips on both sides so squeeze and pull to remove the connector). Recheck the voltage at the battery itself across the + and - terminals, then at the fuse on the furnace circuit (fuse to fuse box ground), then at the connector between the double wire and the ground pin of the connector. All three should be very close under the same charge conditions (while plugged in your 3 stage battery charger will first charge at a high voltage - around 14 volts - then taper down to high 13 volt range then down to a lower float voltage). If you find the voltage more than 0.2 to 0.4 volts difference between any of these three measurements you have too high a resistance somewhere in that circuit. As I
indicated in my first post, on a Royale, since the refer and furnace are both on the drivers side, it is easy to drill a small hole in the cabinet wall between them and run a new + and - wire from the connector on the side of the furnace to the terminal on the refer to get reliable + and ground to the furnace if need be.
If the voltage is nearly the same in all three places then plug the connector back in and set the thermostat to call for heat. You should hear the fan come on and a short time later hear the furnace light. If the fan comes on but the furnace does not light, then you have either a weak fan motor (not turning fast enough), a bad sail switch (the combustion side fan on the blower has to move enough air to lift the sail switch), a bad limit switch, a bad board, a bad propane solenoid (rare) or a bad igniter, or you are out of propane! Be sure the propane valve is open on the tank and you have enough propane by lighting a burner on the stove.
Take the front cover off of the furnace (two screws) and on the bottom left side you will see a window into the burn chamber. Set the thermostat to call for heat and watch in that little round window to see spark from the igniter and then flame from the burner. One last test if the furnace still does not come on. Cut the two blue wires on the connector and twist them together. That will simulate the thermostat calling for heat. If the furnace still does not work, you have to start testing/replacing components one by one to find the bad one.
There are times when these old furnaces seem to have a mind of their own when it comes to running or not and you may be faced with replacing it if you can't find the reason for this unreliable performance. The furnace is easy to remove. Close the propane valve at the tank or at the furnace if there is a shutoff there. Remove the propane line from the furnace, unplug the connector, remove the front cover and see if there are any screws holding the furnace to the wooden stand on which it sits. Go outside and remove the screw from the center of the exhaust. It is a long screw and has to come all the way out. You may also need to remove the four screws holding the air intake and exhaust plate to the coach wall. The furnace should just slide out towards the inside of the coach but the air intake and exhaust pipes between the outside wall plate and the furnace may have rusted together so could take some persuasion to come apart. I would not suggest this removal process in t
he cold until you have a new replacement furnace in hand.
If your two electric heaters just can't keep up and you are near a hardware or sporting goods store you can pick up a Mr. Heater or other brand infrared propane heater for $70 to $150 that work on one pound bottles of propane. A one pound bottle will last a couple of hours or more depending on the heat setting and they will heat up the interior on a GMC fairly quickly. Crack a window or open the top vents. Hope this helps.
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
==============
Message: 2
Date: Thu, 9 Apr 2015 23:48:42 -0500
From: Bob Dunahugh
To: "gmclist@temp.gmcnet.org"
Subject: Re: [GMCnet] Help. 30 degrees out with snow. Furnace not
lighting.
Message-ID:
Content-Type: text/plain; charset="iso-8859-1"
Thanks Jerry. I have a 78 Royale. Checked the voltage at the house fuse that feeds the furnace. 13.783 volts. I'm plugged into shore power. So what would you consider low voltage at the furnace? I've got two electric heaters to get me by. Not the best. But beats 27 degrees. Bob
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Jerry & Sharon Work
78 Royale
Kerby, OR
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