2015 roo 23ss

[Superstroker1]

I’m having trouble with the furnace it works when plugged in or on a generator but the minute you unplug it or shut the generator off it work not work on battery’s alone the battery’s are brand new and fully charged any help would be appreciated
Thanks

[Larry-NC]

Originally Posted by Superstroker1

I’m having trouble with the furnace it works when plugged in or on a generator but the minute you unplug it or shut the generator off it work not work on battery’s alone the battery’s are brand new and fully charged any help would be appreciated
Thanks

Do you have lights when the unit is unplugged and generator off, or is it just the furnace? If you have a complete loss of power, you need to check the resettable circuit breaker mounted on the frame, between the battery and the rest of the trailer. There's a tiny button on the end, above the mounting screw. Press it in until it clicks.

[Superstroker1]

Yes everything else works lights water pump the exhaust fans it only the furnace it turns on for a few seconds but then shuts back off almost like it’s not igniting but runs fine when plugged in

[Chuck_S]

Just 'cuz the battery is "new" doesn't mean it's fully charged as I've found out.

Battery voltage when not connected to generator or shore power is what? Just turn the converter circuit breaker Off to be sure. Mine is marked Conv in ball point pen. Should be 12.6 to 12.7 volts. Measure at the battery and at the power center.

-- Chuck

[Superstroker1]

Battery’s measure at 12.6 not sure where the power center is

[Chuck_S]

You know where it is. The power center is where all the fuses and circuit breakers are. Commonly and incorrectly called the "converter" by many. Mine is under the refrigerator with a flip down door.

Battery voltage is indicating full charge assuming neither shorepower nor a generator were connected. Keep your voltmeter connected to the battery and turn the furnace back on with the temperature set to a ridiculous high temperature. Note what the voltage reads while the furnace is running. Any massive voltage drop?

You can "load test" the battery by keeping shorepower and generator off and turning on everything powered by 12vDC and seeing if the power cuts out. The furnace draws about 3.4 amps so turning the bathroom fan speed to high (2.7a), range hood (1.3a) will draw about 4 amps and approximate the draw of the furnace. Interior lights will add to this. I don't think this is the problem but it's easy to check.

-- Chuck

[Superstroker1]

The voltage ranges from 12.7 to 12.5 with the furnace on and a few lights

[rsdata]

Originally Posted by Superstroker1

The voltage ranges from 12.7 to 12.5 with the furnace on and a few lights

assuming you measure the battery not plugged into shore power or generator?

A fully charged battery is always 12.6 VDC or more with no load, so sounds as if your battery is fully charged.

[Larry-NC]

Originally Posted by Superstroker1

The voltage ranges from 12.7 to 12.5 with the furnace on and a few lights

If you made that measurement UNPLUGGED, with NO GENERATOR and NO SOLAR PANELS, that indicates the battery has a good charge and is fine.

Now, how about telling us a little more. You wrote that the furnace "works" when on shore power or generator, but not on battery. What exactly do you mean by "works?"

When a Suburban in working condition starts, its blower runs for around 15 seconds, purging unburnt gases (in case there was a failed prior event). There are actually two separate blowers: One circulates air within your unit. The other brings in fresh air from the outside to the combustion chamber and exhausts burnt gas to the outside. Do you hear the blower run? Can you feel the air at the outside port, either flowing in or out?

Then the furnace attempts to light. You have to listen closely to hear it over the blower sound. You will hear a "clunk" as the gas valve opens and then "click-click-click" as an electric spark attempts to ignite the gas.

There are a couple of more steps, but let's stop here for now. Try this with shore power and see if you can identify the sounds. Then try on battery and report what you here, and the difference if any.

[Superstroker1]

When hooked to shore power I can hear the sounds your saying and hear the furnace light
When not hooked to shore power just using the battery’s you can here the blower turn on but not the clunk sound of the gas or the click click to ignite

[Larry-NC]

Originally Posted by Superstroker1

When hooked to shore power I can hear the sounds your saying and hear the furnace light
When not hooked to shore power just using the battery’s you can here the blower turn on but not the clunk sound of the gas or the click click to ignite

Good, making progress. For safety reasons, there is a fin in the blower air path. If there is sufficient air flow, the fin (called a sail) moves to one side, out of the air path and actuates a switch (sail switch),which allows the gas valve and igniter to actuate.

The blower is a typical DC motor, speed dependent on voltage. That's why everyone was after you to check the battery voltage; if it's too low the blower speed will be low and the sail switch won't actuate.

We haven't asked, but we are guessing you have the common Suburban SF-series (SF-25, SF-35, etc.) furnace. Is that correct?

What we need to do now, just to be sure, is to check the voltage at the furnace. It "should" be the same as at the battery, but let's be sure, if you can do it. An easy way to do this is to remove the thermostat cover and measure between the OFF and HEAT terminals of the switch on the thermostat when the switch is in the OFF position.

A more difficult way would be to measure between the red and yellow wires going to the control board. If you can see the wires going into the furnace but no connections, you could skin a little insulation off the wires, make your measurement, and wrap the bare spot with electrical tape.

If this measurement is above 12 volts, then the control board is suspect.

EDIT: Or there is insufficient airflow at 12.6 volts. Only sufficient airflow when the voltage is even higher. These motors are not supposed to be lubricated and it's rare to hear that one has bound up. But we frequently hear that there's an airflow restriction. Go to the outside furnace vent and make sure that wasps or spiders have not built a nest in the intake or exhaust port.