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blown fuses in new FWC Hawk Atwood furnace

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#1 mthunter

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Posted 13 November 2018 - 08:40 PM

Hi Folks,

This is my first post to this forum. I'm sharing this story so others might learn from my experience, but also to see if anyone has had similar issues, or was aware of the fuse issue I ran into. 

 

I purchased a 2018 Hawk FWC in October of 2018. So far, I've really enjoyed it and everything has been working fine. 

 

Last weekend, I took the camper out hunting in Southwest Montana. It's winter here, and temperatures dropped to 10 degrees F at night. The furnace was really key. It worked fine on our first day, but the following afternoon, it would not start when I turned on the thermostat. Plenty of propane, and the propane range worked fine, so I knew it was electrical. I checked the 7.5 amp fuse for the Atwood furnace and it had blown. I swapped in the 7.5 amp fuse for the interior lights and it immediately blew as well. 

 

At this point, I had no extra fuses, no heat and no lights. I tucked tail and headed for home. This was my last hunting trip of the year, and I was disappointed, to put it mildly. 

 

I emailed the FWC support folks, and was told that Atwood had recently changed their recommended fuse from 7.5 Amp to 15 Amp. Sure enough, I swapped in the 15 Amp fuse and the furnace works fine. Lesson learned, I'll carry a few extra fuses now when I travel. 

 

If anyone else was aware of this change, or has experienced similar issues, I'd be interested in hearing your story. 

 

Cheers. 

 


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#2 Advmoto18

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Posted 14 November 2018 - 12:57 AM

Good question and welcome to WTW!

 

While I have gleamed a lot of good info from the FWC folks, I think I would contact Dometic ( Atwood is now wholly owned and branded under Dometic).

 

Increasing fuse amperage by 100% does not sound right to me.

 

I am NOT an EE, but, as a retired airline pilot, we got more than our fair share of training on electrical systems and componets.

 

My next door neighbor is an EE and he offered this info...

 

"The MAXIMUM fuse rating should be no MORE than 50% of the maximum current load a wire can handle."
 
So this begs the question, what is the smallest gauge wire used inside the unit?
 
For the sake of discussion only, if 12 gauge wire is installed, then max amperage as 18.6A which means you should never use larger than a 10A fuse (9.3A is actually 50% for 12 gauge wire but good luck finding a 9.3A fuse).
 
So jumping from the installed 7.5A fuse to a 15A fuse in this case would give me pause until I had written verification from Dometic.  This is a good way to smoke check your electrical system if FWC info isn't quite right or got lost in translation.
 
I'm not saying 15A fuse isn't recommended.  I'd simply want written verification from Dometic in order to sleep soundly at night in my camper with the heater running.

Edited by Advmoto18, 14 November 2018 - 01:00 AM.

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#3 Vic Harder

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Posted 14 November 2018 - 03:21 AM

not to mention that with more than 7 amps of draw, your batteries are not going to last long
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#4 mthunter

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Posted 14 November 2018 - 03:29 PM

Thanks guys, this is very helpful. I don't know much about electrical systems, so I'm not very comfortable diagnosing these kinds of problems. 

 

I will follow up with the FWC warranty folks and Dometic/Atwood and post whatever I find. 

 

And a quick follow up, I tried running my furnace again last night with the 15 Amp fuse and it now fails to start. I tried connecting with shore power and this didn't help. 

 

So I'm stuck like chuck...Let's hope the FWC service and warranty department is good. I don't feel like this should be happening with a 6 month old camper. 

 

Thanks again! 


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#5 mthunter

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Posted 14 November 2018 - 05:22 PM

Jay at FWC sent me this furnace trouble shooting guide. I'll step through this myself tonight. I'm posting it here in case it is helpful for anyone else. 

 

Furnace Trouble Shooting Guide

 

Note: Trouble Shooting Guide in Manual on Page 25

 

# 1. How old is the unit? what is the date of purchase?  Customer Name?

 

# 2. Is the propane turned on?

 

# 3. Have you tried switching propane tanks?

 

# 4. What is the elevation of the unit?

 

# 5. Does the stove ignite?

 

  1. if the stove does ignite, is there a noticeable difference between full output and quarter output?
  2. if the stove does not ignite, is the propane on?

 

 

# 6. What is the battery voltage reading?

 

# 7.  Once the thermostat is turned on inside your camper, does the furnace blower fan come on?

 

 

# 8.  If the blower fan does come on, after approx. 15 seconds, can you hear a small burst of faint clicking noises (the sparker trying to ignite)?

 

 

 # 9.  Once the blower fan has been on for 15 seconds, can you smell any propane exhaust coming from the exterior exhaust vent?

 

 

# 10.  If the blower fan comes on, and the igniter is clicking, does the furnace fire up and start burning propane, even if for only a few minutes?

 

 

Additional things to check . . .

 

# 11.  Please check the small fuse on the furnace circuit board to make sure it has not blown?

 

# 12.  If none of the above has helped, can you please try to flip the “reset” switch to the “off” position, wait 60 seconds, and the flip it back to the “on” position. Hop back inside your camper and turn the thermostat “on” and see if you can get the furnace to start up?

 

 

Once you have Answers or have tried the above, please take notes and report back to us with your findings.


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#6 iowahiker

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Posted 14 November 2018 - 05:41 PM

FWC rated the 12,000 btu Atwood furnace in our camper as drawing 3-4 amps when we purchased our camper.  Searching online shows no disagreement, 3-4 amps, for the 12,000 btu model.  Using a 15 amp fuse on a 3-4 amp device is an interesting choice.   


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#7 Wallowa

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Posted 14 November 2018 - 06:32 PM

MTHunter...interesting trouble shooting steps from FWC...missing were any causes [other than no propane or electrical power] or remedies...first I guess ID the weak link...

 

Hopefully you can remember the name of the person @ FWC recommending a 15 amp fuse...


Edited by Wallowa, 14 November 2018 - 06:33 PM.

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#8 mthunter

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Posted 14 November 2018 - 06:54 PM

Thanks all for the comments and support. 

 

Jay Roper was the person at FWC who suggested the 15 amp fuse. 

 

Further reading outside this forum on Atwood/Dometic furnace problems has revealed that others have had similar issues with these furnaces in other types of campers. Here is an example. One of the posts notes that an Atwood/Dometic furnace mobile technician (they have those, really?) suggested the 15 amp fuse. 

 

http://www.forestriv...ses-122937.html

 

Thanks again, I'll update this when I figure things out. 


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#9 Advmoto18

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Posted 16 November 2018 - 12:41 PM

Continuous draw amperage will be less than amperage required to "light-off" the unit.  "Light-off" is a momentary increase and generally several amps more than continuous draw in units such as this.

 

Likewise, I saw continuous draw to be 3-4 amps in the online docs for the "small" Dometic furnaces and thought a 7.5A fuse to be appropriate to handle increased amperage during "light-off".  

 

Which caused further head scratching on my part (and concern) when I read the advice to install a 15A fuse.


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#10 Wallowa

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Posted 16 November 2018 - 03:53 PM

Stan are you out there?  Comments from FWC?


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