# Hydro Flame furnace problem



## Jim.UT (Jul 30, 2009)

I've dug my Elkhorn 11Z camper out of mothballs after 2 years of sitting. I now find that the furnace doesn't seem to function AT ALL. 

The furnace is a model 7920-II. The camper is a 1995 model. The furnace installation manual is dated February 1994.

Normal procedure on this unit is to turn the thermastat switch to "on" and then turn the heat setting up. After a few seconds (maybe 30) the furnace fan will start to blow and then the autolighter will fire the propane.

In my case I get nothing by turning the unit on. No fan....nothing. I've checked the fuse panel and the furnace fuse is OK. I got out my trusty test light and found juice at the connection behind the black plastic thingy that's labeled "5 amps" on the front. I have power at both terminals on that item. Tracing the red wire to a relay I find power at the connection where the red wire connects but nowhere else. I've put my test light on every wire connection I can reach and get no power anywhere other than where I've described.

Any ideas?


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## DL Rupper (Jul 31, 2009)

Re: Hydro Flame furnace problem

How hot is it inside the camper?  Can you turn the thermostat to a higher heat setting than the temperature of the ambient air inside the camper?


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## Jim.UT (Jul 31, 2009)

Re: Hydro Flame furnace problem

I was doing this test early in the morning while it is still cool. I have the thermostat up to the max (90). I understand it won't work later in the day when it's over 90 outside.

Yesterday I replaced both coach batteries. This morning I tried the furnace again in the hopes that the problem was due to a marginal battery. Still nothing.

However, my fridge is now working MUCH better with the new battery.


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## utmtman (Jul 31, 2009)

Re: Hydro Flame furnace problem

Could be a blown fuse in the fuse box, have you checked them out.    Where you at the Ut, were down in Carbon County.


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## Jim.UT (Jul 31, 2009)

Re: Hydro Flame furnace problem

Fuse is good. That was the first thing I checked. I have power into the furnace at one point, but can't find power at any other connection and I don't know where I should expect to find power.

I'm in Heber City. Trying to go to Red Canyon (near Bryce) next week. I guess we'll survive down there without a furnace.


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## DL Rupper (Jul 31, 2009)

Re: Hydro Flame furnace problem

Hey Jim UT from Heber City.  You ever hear of Wallsburg, UT (nearby Heber City).  It was named after my Great-Great Grandfather William Madison Wall.  Small world. 

You shouldn't need a furnace anywhere near Bryce.  We were campground hosts in Capital Reef Natl Park just a couple of mountains over from Bryce and never needed a furnace from May through Aug.


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## Jim.UT (Jul 31, 2009)

Re: Hydro Flame furnace problem

Hey, I've been to Wallsburg many times! Bryce is pretty close to Capitol Reef, but about 2000 feet higher in elevation. It can get cool at night even in the summer. Still not cold enough to worry about no furnace for this trip.


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## Kirk (Jul 31, 2009)

Re: Hydro Flame furnace problem

Let me suggest that before you go too far, visit Bryant RV's website at http://bryantrv.com/docs.html

Your furnace was built by Atwood, the owner of the Hydro Flame line of RV furnace. I would start by down-loading a copy of the service manual. 

From what you have told us, it is just a matter of guessing what the problem may be. Since you have power to the furnace, the next question is whether or not the thermostat is getting 12V to send a signal to the furnace? In a 1995 model RV you probably have one of the old bimetallic strip thermostats and if so you can easily remove the cover from it and check for a voltage there. If it is there, next make sure that the contacts close and that they make a good connection to supply that 12V signal back to the furnace to cause it to start.

Normal operation for an Atwood furnace is for the blower to start shortly after the thermostat closes, and after about 30 seconds of blower operation, the gas valve should open and the igniter should fire to start the flame. Since the blower does not start, there can be no further action because there is a "sail switch" that is in the air path which closes once there is enough air movement for save combustion and that then supplies the power to the igniter circuit board which then triggers the gas valve and the igniter.

There is also an over temperature thermostat on the furnace heat exchanger but if it were open it would not prevent the blower from operating. I suspect that you problem is either just inside of the furnace, where the connections are or, in the circuit that contains the thermostat.


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## utmtman (Aug 3, 2009)

Re: Hydro Flame furnace problem

I wish I had got back here sooner Jim, Atwood is located in Salt Lake and if you call them they will walk you thru checking and testing things.  If you get that one girl she is the best of the three techs.  Also you can take it to the rv place about 3200 south state in Salt Lake, they are atwood reps.


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