First Night in New Hawk. Furnace Question

[Slowride]

Thought I'd post a pic because, well, we all like pics right?

So, first night out. Not nearly as cold as I anticipate camping in, temps got down to the low 30s. High 30s until the wee hours. About 10 pm I get in and turn on the heater and it fires up and performs as it should. In no time my camper is over 60 degrees and I'm excited. I've never camped with heat before. Maybe I'm getting soft, but this felt good! I went to sleep with the heater cycling on and off, all is well.

Woke up about 3 AM to a very cold camper. Obvious heat was no longer on. I turned the thermostat off, and then back on. The fan in the furnace started turning strong. For less than a minute and shut off never igniting. I repeated a couple of times with same result. Voltmeter was reading 12.7 and I figured it wasn't power because the fan was at what sounded like full speed. Correct me if I'm wrong but I assume the fan is the biggest draw on the furnace. So I figured it wasn't a low battery. I check propane and tank felt heavy so now problem there. I started wondering if I need to troubleshoot something inside the furnace, but not in the middle of the night.

Here's where it gets odd. Just to be sure I go ahead and fire up my truck. Voltmeter reads 14+ V with truck charging. I turn thermostat off then on again and furnace fires right up. Runs like a champ. Warm camper turn off truck and furnace cycles again as I go back to sleep. Wake up before 6 AM (which is when I was getting up anyway) to same cold camper no heat, voltmeter around 12.6V, starting truck makes everything ok

So what gives? Is it possible that my battery was discharged further than the voltmeter would indicate?

I also tried to reproduce this scenario at home by running heater at max with doors/vents open. Ran about 4 hours straight, voltmeter down to 12.3 and fired right up again, no problem. Wondering if this is common or any ideas? I'd like to head up to the hills here and snow camp, but would rather not troubleshoot in the middle of the night

 

[Karlton]

Hey Slowride - love the photo. Tell us about the battery set-up in your Hawk and the voltmeter you are using.

 

[Jack]

If the fan does not reach full speed, the furnace won't light and will subsequently shut off. Can you hear/feel a difference in fan speed/cfm? Low voltage at the furnace is the usual culprit for this. With a DMM (voltmeter), can you measure the voltage at the furnace and at the battery and then with the truck running? Possibilities are a loose wire connection to the furnace or something else is drawing down the battery voltage at the same time. The circuit board in the furnace is another possible culprit. I once had to replace one.

 

[Slowride]

Hey Slowride - love the photo. Tell us about the battery set-up in your Hawk and the voltmeter you are using.

Single battery from FWC, I believe 90 Amp Hour AGM

The voltmeter that evening I was reading was the one installed on the furnace cabinet, which I've confirmed with a voltmeter at home that it reads the same as measured at battery terminals. (battery in the camper)

 

[Slowride]

If the fan does not reach full speed, the furnace won't light and will subsequently shut off. Can you hear/feel a difference in fan speed/cfm? Low voltage at the furnace is the usual culprit for this. With a DMM (voltmeter), can you measure the voltage at the furnace and at the battery and then with the truck running? Possibilities are a loose wire connection to the furnace or something else is drawing down the battery voltage at the same time. The circuit board in the furnace is another possible culprit. I once had to replace one.

Well that is good to know. The fan was not running obviously slower just by listening. I suppose it could have been less but I didn't notice. IF that was the case wouldn't the fan have been running that slower or weaker when it read 12.3V at home?.

Maybe another question I should ask for those of you with experience is at what voltage reading would I typically expect the furnace to stop running? I know it's not perfect but from what I've read 12.4V should be at about 50% on this battery

I haven't opened up the furnace yet as I wasn't sure where to start looking. Troubleshooting guide in the manual didn't match my scenario at all. Biggest problem is right now everything works fine (I hate those sort of problems)

 

[Karlton]

Perhaps start with a fully charged battery and run the furnace noting the drop in voltage over time and when the furnace will not kick back on. This will give you an indication as to the voltage drop and furnace performance. If you check every 15 min, you'll have the window where it shuts off.

I have 2 74-amp hour AMGs with a Victron BVM and noted that on a cold night when running the furnace all night the battery charge was down to about 65%. I just went out to my Hawk and turned on the furnace and noted that when producing heat, it drew 1.75 amps. There are folks on here who are wizards at understanding how much power each feature uses and how long you can run your battery, I tend to just get by.

I did install the Victron BVM 712 and it is really intuitive to understand how much power you are drawing and how long you can run the camper on the batteries.
https://www.victronenergy.com/battery-monitors/bmv-712-smart

 

[Slowride]

Perhaps start with a fully charged battery and run the furnace noting the drop in voltage over time and when the furnace will not kick back on. This will give you an indication as to the voltage drop and furnace performance. If you check every 15 min, you'll have the window where it shuts off.

I have 2 74-amp hour AMGs with a Victron BVM and noted that on a cold night when running the furnace all night the battery charge was down to about 65%. I just went out to my Hawk and turned on the furnace and noted that when producing heat, it drew 1.75 amps. There are folks on here who are wizards at understanding how much power each feature uses and how long you can run your battery, I tend to just get by.

I did install the Victron BVM 712 and it is really intuitive to understand how much power you are drawing and how long you can run the camper on the batteries.
https://www.victronenergy.com/battery-monitors/bmv-712-smart

That's almost what I did at home by trying to replicate the situation when I ran the furnace for over 4 hours. That was straight running as I set the thermostat high enough that it wouldn't shut off, so I figured it was actually simulating how much the furnace would run over a longer period if it was cycling. I even ran one of the vent fans on high as well just to speed up the process of discharging the battery. Down to 12.3 and worked fine. So I already see that reading is not a consistent part of the equation.

I hear you on just trying to get by lol. I often find with electrical things theory doesn't always meet reality....and often it's because I'm missing one or more other variables. I would think if the furnace only draws 1.75 amps then 90AH should be plenty even if leaving a 50% reserve, But what do I know, I'm sure I'm missing something there as well

 

[heinphoto]

What was the elevation where you were camping? The higher the elevation, the more likely there will be potential issues with the sail switch activating. So it might be fine and home, but problematic when you camp at higher elevations. I have also seen several reports recently in various places where the short length of flexible ducting behind the furnace "grate" on the cabinet inside the camper can cause enough back pressure and reduction in flow to prevent the sail switch from activating. In those cases removing the ducting solved the problem.

 

[Slowride]

What was the elevation where you were camping? The higher the elevation, the more likely there will be potential issues with the sail switch activating. So it might be fine and home, but problematic when you camp at higher elevations. I have also seen several reports recently in various places where the short length of flexible ducting behind the furnace "grate" on the cabinet inside the camper can cause enough back pressure and reduction in flow to prevent the sail switch from activating. In those cases removing the ducting solved the problem.

hmmm very interesting.

i was at relatively low elevation, about 4,000' or so. Back home is basically sea level, so there is a difference there.

Would either of those be intermittent problems?

 

[campito]

as a data point, I frequently camp at 10k+ ft and have not had a problem in a 2012 (don't know if its the same furnace and design)

 

[Slowride]

as a data point, I frequently camp at 10k+ ft and have not had a problem in a 2012 (don't know if its the same furnace and design)

Thanks, any insight appreciated! Single or dual battery?

 

[heinphoto]

hmmm very interesting.

i was at relatively low elevation, about 4,000' or so. Back home is basically sea level, so there is a difference there.

Would either of those be intermittent problems?

as a data point, I frequently camp at 10k+ ft and have not had a problem in a 2012 (don't know if its the same furnace and design)

There are several potential points of failure with the furnace (propane, thermostat, sail switch, electronics board, etc.) - FWC has a very good troubleshooting video you should watch if you haven't already.

The sail switch is particularly prone to problems. It is a safety interlock device that activates when it senses sufficient flow in the furnace to allow safe operation. Anything that prevents it from activating will prevent the furnace from firing up (the fan will turn on but the furnace won't spark and fire). For example, accumulation of dirt, dust, pet hair, etc. on the sail switch can prevent it from activating. However, I wouldn't expect this to be the problem on a new camper. Some combination of low battery, back pressure from the ducting, or high elevation/low pressure could reduce the air flow enough to prevent it from activating. This could definitely be intermittent since it could depend on the sensitivity of your particular switch, the battery level, and atmospheric pressure. Some people have found that removing the ducting increases the air flow enough to allow the furnace to fire up in cases like this. Sometimes the sail switch just fails and needs to be replaced (some have started carrying spares just in case).

With that said, We haven't yet had any problems with the furnace in our 2020 and we have used it several nights at 9000-10000'. However, the furnace used in newer campers does seem to be more problematic. I'm not sure what year they changed, but I'm guessing the 2012 has the older, more reliable furnace.

 

[campito]

Thanks, any insight appreciated! Single or dual battery?

dual

 

[JWL]

Many oh us with new Hawks have had the same problem. The problem most of the time seems to be that the furnace duct is going from right to center cutting off the airflow. A quick fix is to take the entire vent face and the duct work off. That worked for me the first time it happened. Next I pushed as much of the flexible duct back on the furnace opening as I could and left a little bit on the vent cover. I just spent several nights in 30 degree temps and I am VERY happy to say it worked. FWC is aware that this is a problem.

 

[JWL]

Here are some photos of how it looked after I scrunched the duct and one showing how the furnace sits off to the right with only a little space for the duct to go to center.

 

[Slowride]

There are several potential points of failure with the furnace (propane, thermostat, sail switch, electronics board, etc.) - FWC has a very good troubleshooting video you should watch if you haven't already.

The sail switch is particularly prone to problems. It is a safety interlock device that activates when it senses sufficient flow in the furnace to allow safe operation. Anything that prevents it from activating will prevent the furnace from firing up (the fan will turn on but the furnace won't spark and fire). For example, accumulation of dirt, dust, pet hair, etc. on the sail switch can prevent it from activating. However, I wouldn't expect this to be the problem on a new camper. Some combination of low battery, back pressure from the ducting, or high elevation/low pressure could reduce the air flow enough to prevent it from activating. This could definitely be intermittent since it could depend on the sensitivity of your particular switch, the battery level, and atmospheric pressure. Some people have found that removing the ducting increases the air flow enough to allow the furnace to fire up in cases like this. Sometimes the sail switch just fails and needs to be replaced (some have started carrying spares just in case).

With that said, We haven't yet had any problems with the furnace in our 2020 and we have used it several nights at 9000-10000'. However, the furnace used in newer campers does seem to be more problematic. I'm not sure what year they changed, but I'm guessing the 2012 has the older, more reliable furnace.

thanks. Lots of good info there.

I'll have to check out the video

 

[Slowride]

Many oh us with new Hawks have had the same problem. The problem most of the time seems to be that the furnace duct is going from right to center cutting off the airflow. A quick fix is to take the entire vent face and the duct work off. That worked for me the first time it happened. Next I pushed as much of the flexible duct back on the furnace opening as I could and left a little bit on the vent cover. I just spent several nights in 30 degree temps and I am VERY happy to say it worked. FWC is aware that this is a problem.

Curious if this showed up as an intermittent problem?

 

[Dphillip]

This is very good information, I’ve had the same issues with my 2015 Hawk’s furnace whereas it will run properly for a few hours then shut off in the middle of the night never to restart. I switched out the factory thermostat for a digital readout unit but the problem persists. I’ll now be checking the duct work by the vent.

 

[JWL]

Curious if this showed up as an intermittent problem?

somewhat, in the fact that the first trip I tried it before we left, it came on and I shut it off. On our trip, turned it on in the morning, it fired up for a bit and shut off, never to fire up again. I started digging through everything. The other couple we were with has an older Fleet and he has been through the whole “it’s the sail switch” thing from day one with his rig. So after swapping propane tanks, opening the back we tried opening the front. Bingo! It came on and stayed working the rest of the 4 days out, with the face plate off.
It took me several tries to get the duct work tight enough not to cross over, I didn’t want to cut it and risk “voiding the warranty”. The only thing left to see is if this will still work at altitude. But that is going to be awhile off cause I live in Texas.

 

[Norsman]

I have a Hawk with dual 6v batteries, I can run the heater all night and have done so many nights in subfreezing temps. I just can’t run this battery down, and the solar panel has it topped off in 1-2 hours of even cloudy sky the next morning.