2024 310GK Furnace works on batteries/Cuts off when on shore power

[Boxer1200]

This one has me stumped....

As the title states, the furnace works as advertised on battery power. When hooked up to shore power, it'll run for 15-20 minutes and shut down. Won't work again till it rests and I cycle it at the thermostat by going from heat to off and back to heat. When I first purchased the unit a few weeks ago it did this in both power configurations. Dealer bench tested, took it apart looking for issues etc. Ran it for extended periods. Couldn't find a problem and it worked great at their shop. I tested it there before I brought it home without shore power and all was good. Got it home and as I said, great on batteries, not so good on shore power. Not the end of world since summer is approaching, but wondering what odd electrical stuff I may have going on. Any ideas as to what may be going on so I can steer the dealership a little. I'll add too that it just shuts off. It's not loss of heat with fan only and then done. Just all done at once. Lastly, my converter is parked right next to a heat duct. Don't know if that could cause issues due to excessive heat.


Thanks.

[TucsonJim]

Hi Boxer1200

I'm curious if your 12 volt battery voltage differs much from your 12 volt converter voltage. Try the following experiment.

1. Use a volt meter to measure the voltage at the battery terminals while plugged into shore power.
2. Disconnect from shore power, wait five minutes, and measure the voltage at the battery terminals again.
3. While plugged into shore power, run the furnace for 10-15 minutes and see if the voltage at the battery terminals changes substantially from measurement 1.

If they are significantly different, it may be that the control circuits are voltage or temperature dependent.

If the voltages are similar, I'd try moving the converter away from the heat duct to see if it makes a difference.

Jim

[Boxer1200]

Thanks Jim. I'll try this out today and report back what I come up with. Should turn off the solar cutoff as well if sunny just to get a true baseline?

[Scott'n'Wendy]

Once it faults out while on shore power, if you unplug the shore power cable it will run normally again?
If it does maybe the converter is set too high? Similar conclusion as Jim. But an easy test for this if you don't have a meter would be to have your shore power plugged in and the converter breaker off. Turn on the lights. Note their brightness. Flip the converter breaker on and see if they brighten up significantly. If this is the case it may be causing the furnace shutdown with a high DC+
I don't think that heat duct would be an issue...but...I've been wrong before.....

[Boxer1200]

Once it faults out while on shore power, if you unplug the shore power cable it will run normally again?
If it does maybe the converter is set too high? Similar conclusion as Jim. But an easy test for this if you don't have a meter would be to have your shore power plugged in and the converter breaker off. Turn on the lights. Note their brightness. Flip the converter breaker on and see if they brighten up significantly. If this is the case it may be causing the furnace shutdown with a high DC+
I don't think that heat duct would be an issue...but...I've been wrong before.....

It'll run again, but not on it's own. I have to cycle it as the thermostat. Really odd. I tried every combo I could think of today. Batteries off/on, solar on/off, Shore power/no shore. Only thing that works past 17 minutes is batteries alone(solar on too). I ran into a mobile RV tech and asked if he'd ever come across this. Never heard of it. Tried a new power chord realizing that the dealer didn't use my chord when they did all their work. Also picked up a PI surge protector so I could see what was going on at the power source. Been putting that off for years and seemed like a good investment anyway. All good there. Finally I moved the converter and no dice as you suspected. This one is an enigma. I'll try that experiment next.

[Scott'n'Wendy]

What were the battery voltages with or without shore power or did you see if the lights brighten up?

[Boxer1200]

Didn't get a chance to do the experiment. We're leaving on a four day trip tomorrow to Big Bend area in Texas. I'm sure I'll find some downtime tomorrow evening to tinker, and I'll report back.

[howson]

Didn't get a chance to do the experiment. We're leaving on a four day trip tomorrow to Big Bend area in Texas. I'm sure I'll find some downtime tomorrow evening to tinker, and I'll report back.

The parts list for your 310GK lists a 12V LOGIC INVERTER RELAY HARNESS C-FFG35FA-A08 for the furnace. I have no idea why this relay is in the circuit nor where it is located, but it's got me curious. I'll see if I can get more info and will post back.

Howard

[Jlawles2]

howson Howard, I wonder if that is used to control the furnace B/C the thermostat cannot do it directly? Just a thought in case the unity board is controlling the A/C and Heating system.

Edit: If there is a heat pump involved, then there has to be something to flip the logic from heat pump to furnace when outside temps or differential temp reaches a certain point.

[howson]

Didn't get a chance to do the experiment. We're leaving on a four day trip tomorrow to Big Bend area in Texas. I'm sure I'll find some downtime tomorrow evening to tinker, and I'll report back.

Can you confirm if the furnace is a Furrion or a Suburban? Specific model, please.

[howson]

Boxer1200
What I've found out is the relay harness is applicable if there's a Furrion furnace installed. There's not many with that configuration (a guess).

If the furnace is a Suburban SF-35VHQ, these models have been known to have motor issues. See https://gdrvowners.com/forum/operati...f-35vhq-issues

If you have a DC clamp meter, seeing the furnace motor's amperage when running on battery and then on shore power would be most interesting to know. I'm guessing there will be a difference and that difference is the voltage difference. (Probably what TucsonJim was thinking back in post 2.)

If you don't have a DC clamp meter, if you have a battery monitor with a shunt that could tell us the amperage, too. At minimum, measure the voltage with the furnace running in both scenarios.

Howard

[ajg617]

Can you confirm if the furnace is a Furrion or a Suburban? Specific model, please.

This is kind of important. We had a problem where the furnace would light on electric but not gas. Turned out to be a disconnected wire on the gas switch of the control panel. But while researching this, came across many issues specific to the make/model of the furnace, including the converter, a circuit board on the back of the furnace, the high temp limit switch, There were many differences between model of the Suburban furnaces installed.

[Boxer1200]

Sorry for the delay. 10hr drive back from our trip and back at work today.

The furnace is a suburban SF35. Or whatever the new one is that replaces that now. I did try switching off the converter on the trip. There was a momentary flicker of lights turning it off and on, but I’d say that’s normal. Light intensity was the same.

I’m leaning towards this being an overheat issue. My reasoning is this. One, very little air flows from the island vents or the bathroom vent by the toilet. Looking into the island through the forward vent, the ducting was twisted constricting the flow. I opened up the island floor and realigned that duct. It then ran for 30 minutes before it quit. That’s a record. The fact that it ran longer after doing that makes me think this an overheat issue. The only strong flowing vents are the bedroom vent and the vent at the base of the hutch. The bathroom is the worst. Almost non existent. The routing of the duct work off the furnace is not the best. A 90 degree bend on an island duct right off the furnace can’t be good. Also, the bathroom vent is a 2” duct that comes off the furnace but splits into wet bay and somewhere at the back of the trailer. Maybe the fresh tank?

I guess if the blower weren’t running at the correct speed that could cause an overheat. Or just restrictions I can’t see. Also, if I’m understanding the high temp cutoff correctly, the flame could be cutting off and back on without me knowing before it finally just gives up and the whole deal(flame and blower) shut down. Hence the thermostat still saying Heat On when nothing is happening.

My previous FW was larger by 2’. Same layout. If I ran that heat for 30 mins I’d be melting. I’d never run it that long. Mine is 20-30 mins total run time to squeeze out 10 degrees from 55-65. The basement on the other hand is crazy warm due to heat radiating from heater(so hot you cant touch it) And heat blowing out between the back panel and main furnace box where the ducts attach. Is this normal in a Solitude?

Thoughts? Thanks for the all the insight.

[ajg617]

Sorry for the delay. 10hr drive back from our trip and back at work today.

The furnace is a suburban SF35. Or whatever the new one is that replaces that now. I did try switching off the converter on the trip. There was a momentary flicker of lights turning it off and on, but I’d say that’s normal. Light intensity was the same.

I’m leaning towards this being an overheat issue. My reasoning is this. One, very little air flows from the island vents or the bathroom vent by the toilet. Looking into the island through the forward vent, the ducting was twisted constricting the flow. I opened up the island floor and realigned that duct. It then ran for 30 minutes before it quit. That’s a record. The fact that it ran longer after doing that makes me think this an overheat issue. The only strong flowing vents are the bedroom vent and the vent at the base of the hutch. The bathroom is the worst. Almost non existent. The routing of the duct work off the furnace is not the best. A 90 degree bend on an island duct right off the furnace can’t be good. Also, the bathroom vent is a 2” duct that comes off the furnace but splits into wet bay and somewhere at the back of the trailer. Maybe the fresh tank?

I guess if the blower weren’t running at the correct speed that could cause an overheat. Or just restrictions I can’t see. Also, if I’m understanding the high temp cutoff correctly, the flame could be cutting off and back on without me knowing before it finally just gives up and the whole deal(flame and blower) shut down. Hence the thermostat still saying Heat On when nothing is happening.

My previous FW was larger by 2’. Same layout. If I ran that heat for 30 mins I’d be melting. I’d never run it that long. Mine is 20-30 mins total run time to squeeze out 10 degrees from 55-65. The basement on the other hand is crazy warm due to heat radiating from heater(so hot you cant touch it) And heat blowing out between the back panel and main furnace box where the ducts attach. Is this normal in a Solitude?

Thoughts? Thanks for the all the insight.

Just curious, what is the flow out of the register in the bedroom? We also get pretty lame flow out in the main area - why we use the fireplace to help. We also do not get much flow in the bathroom. But, we had a major issue with no heat coming out of the register in the bedroom. Next time you are running the furnace, check the temp in your bath vanity on the right hand side. Where we found the most volume of air coming out was at the coffee bar in front of the pantry. I installed a shut-off register there to regulate flow. Helped quite a bit.

[Boxer1200]

Here’s a pic of my furnace. In looking at it I’m realizing there’s one duct running to the island not two. Must go into a box with two coming off on either side. Per the furnace install manual there should be a minimum of 4 4” ducts coming off the furnace and the one 2” doesn’t count. I’ve got three unless one is hidden and I don’t remember. If so that could cause an overheat as well.