Furnace Blows Cold

pauliwog1980 · 10-23-2022, 04:57 PM

Hi all,
I have an 88 Sunline Satellite and am trying to figure out the furnace. It turns on and blows but doesn't get warm. I can smell the gas and hear it trying to light when I'm by the access panel, but doesn't ever light. Any ideas to try? Sail Switch?

mainah · 10-23-2022, 06:31 PM

It is possible the sail switch isn't working as it is also possable the gas valve isn't working or even a weak battery issue, personally this really isn't something a backyard mechanic shouldn't be playing with.

**JohnB** · 10-23-2022, 06:35 PM

Hi,

Please tell us the model of your furnace to help better, the smaller campers used a different furnace (heat just came out the front vent) and the larger campers has heat ducts across the camper, the furnaces where different. Pics of the furnace help greatly also.

From what you told us, the blower runs, this is a good first step. You said you can smell gas and it trying to light, but it does not seem to want to light? Meaning you do not hear a "whoosh" type sound that the burner was actually burning but you hear clicks from the igniter? Yes or not to each.

Since the blower is running, that means the run signal to the furnace works and the blower runs.

The sail switch should be working as the gas valve and the igniter will not fire if the sail switch is not made and the over temp switch is not tripped.

What this points to, possibly a weak spark from the ignitor or the gas burner and or gas valve orfice is having issues or both at the same time.

We need to know what you have as far as the make/model to help better.

Hope this helps

John

pauliwog1980 · 10-28-2022, 05:24 PM

Thank you for the replies. I checked and cleaned the sail switch and it is definitely working. The blower turns on and I can smell the gas. I hear the clicking of the ignitor but it sounds weak and doesn't light. It tries 2 or 3 times then seems to give up and just keep blowing cold. Attached is a picture of my furnace. Let me know if you don't see it. Seems to be a Model 8520-II. If it is the ignitor, where is it located and how do I replace it?IMG_0821.jpg

**JohnB** · 10-31-2022, 10:15 PM

Many of the igniter control boards do have a feature to shut down trail for ignition upon 3 failed attempts to light. It is a safety feature. If there is no flame sense feed back, it stops trying to light. And yes, the blower keeps running but there will no longer be any attempts to try to light again until the system is reset.

Your furnace is an older one, not sure of your background with this camper, did the furnace ever work when you owned it, how many years was that?

The gas burner has a diffuser screen that sometimes rusts out over time, and the ignitor may not be in the right place do to a mounting issue with the corrosion inside.

Caution needs to be taken on next steps if you have never worked on LP gas appliances. We can't teach you how to look for all the things you may not see or have the gauges to test with. If you have a friend who services home LP appliances, they can help you if you have never worked on gas systems. Or take the camper to a repair place. Only attempt any further work if you have worked on gas appliances before.

You can access the gas burner to see if the burner inside is all corroded and what shape the electrode is in. And you should have the gas valve tested for leaks. On a furnace that old, if corrosion has rotted out the diffuser screen, the gas valve may be corroded inside and not seal up any more either, which means, do not use this system until it is fixed. Finding a new gas valve may be a challenge. It all depends on who port configuration you have. Dometic who now owns the Atwood hydro-flame is discontinuing parts all the time.

This link will show how your gas burner & gas valve will come out as a unit. This is on
a bench test setup. You can remove the burner while the furnace is still in the camper. The gas has to be shut off and the lines purged before removing any parts. All 12 volt DC power from the power converter and including the battery, to be off. The LP gas system will then be opened up after the gas line if removed from the gas valve and no other gas appliances can be used in the camper unless the open gas line is sealed and tested it does not leak. Your burner will look different as this is a newer 8500 series Rev IV style, over your older rev II style, but the same big picture concept is close. Scroll down some in this link until the furnace starts showing up. https://www.sunlineclub.com/forums/f...tml#post154909

Hope this helps

John

Photokit · 11-04-2022, 04:37 PM

Sometimes my furnace will not ignite in my 1850 Saturn TT, and it sounds like you can hear the clicking of the ignition, but, frankly, I never smell gas. for me, usually the problem is electrical, meaning that my battery is not sufficiently charged. In the winter, I often carry two batteries connected pos to pos and neg to neg (I forget what that's called). I use a 100W solar panel to keep the batteries topped off for evening furnace use. A few years ago I had a new mother board installed in the furnace, easy job, done by a pro, and that helped too.