Blown furnace fuse

C.hannah · 11-25-2016, 06:43 AM

I bought a new keystone rv 357 about a month ago have been using every weekend in Alabama. We do not use a shoreline for power. Gas is powering my fridge, stove and furnace. Everything was working fine until I tried to turn the furnace on last night. Everytime I turn it on it blows the fuse. We have gas and the rv. Please help.

Lee · 11-25-2016, 07:27 AM

Can you turn on just the fan? Sounds like the blower motor is drawing to much current. Has it ever worked?

C.hannah · 11-25-2016, 07:36 AM

I will try to turn on just the fan. Last night I did try to turn off the hot water heater and fridge and tried to turn it on again and it blew soon as it kicked on. I am not very "handy . About to head to part store for more fuses.

gkainz · 11-25-2016, 08:20 AM

Please do NOT continue to replace blown fuses. Another new fuse is not going to correct the problem, and for goodness sake, do NOT install a higher rated fuse in an attempt to get your furnace running. The fuse is a safety item to prevent a burned up wire, which could turn into a burned up RV.

Please find a mobile tech or other service person who is knowledgeable in electrical system to assist you.

**chuckster57** · 11-25-2016, 08:34 AM

Quote:

Originally Posted by Lee

Can you turn on just the fan? Sounds like the blower motor is drawing to much current. Has it ever worked?

Furnace wont have fan only option, that is just for the fan in the AC unit.

Low voltage may be the issue, but I suspect it's more than that. As stated putting another fuse in it will be a waste of time and money.

**sourdough** · 11-25-2016, 03:36 PM

Just out of curiousity; what are you doing to charge your batteries? You say you don't use shore power.....just LP. You've been using it the last 3-4 weekends. Without charging your batteries some way you are going to have issues.

CaptnJohn · 11-25-2016, 06:30 PM

Happened to me on maiden voyage 730 miles from home. It was hot and AC running during PDI so the short furnace test seemed OK. The fix is SEMI-easy. It requires a 15 amp slow burn fuse, easy. Semi as finding them is near impossible. Atwood sent one and I ordered 2 online. Safe so no recall and not enough units to warrant a service memo to dealers. Good luck finding one at any auto-parts or hardware store.

xrated · 11-25-2016, 06:39 PM

Anytime an electric motor first starts, there is an inrush of current to said motor. As the motor picks up speed to the rated RPM, the current dies down to the FLA (full load amperage). Electric motors always need a slo-blow fuse or if it has a circuit breaker, there has to be some time delay rating for the fuse or breaker. If the motor circuit does not have a time delay fuse in it (also known as slo-blow sometimes) and the FLA is close to the fuse amperage rating, it will most likely blow.

Having said that, there may be an issue with the furnace blower motor, but usually, the motor for the blower doesn't come on immediately, the bonnet temperature has to come up to a predetermined temperature before the blower turns on. If the fuse is blowing immediately when the furnace is switched on, there is most likely an issue with the furnace.

**chuckster57** · 11-25-2016, 06:54 PM

Quote:

Originally Posted by xrated

but usually, the motor for the blower doesn't come on immediately, the bonnet temperature has to come up to a predetermined temperature before the blower turns on. If the fuse is blowing immediately when the furnace is switched on, there is most likely an issue with the furnace.

That's true for a furnace in a brick and stick house, but not in an RV. In RV's the fan has to start first and create enough air movement to close the sail switch circuit. Once that happens the control board commands the gas valve to open and send current to the sparker to start the flame. Once the thermostat temp is reached, the control board shuts off the flow of gas, the flame quits and the fan continues to run to cool the furnace off.

xrated · 11-25-2016, 11:00 PM

Quote:

Originally Posted by chuckster57

That's true for a furnace in a brick and stick house, but not in an RV. In RV's the fan has to start first and create enough air movement to close the sail switch circuit. Once that happens the control board commands the gas valve to open and send current to the sparker to start the flame. Once the thermostat temp is reached, the control board shuts off the flow of gas, the flame quits and the fan continues to run to cool the furnace off.

Thank you....I learned something today........besides the fact that leftover Turkey is just as good as the T Day serving.

**JRTJH** · 11-26-2016, 05:51 AM

Quote:

Originally Posted by xrated

Thank you....I learned something today........besides the fact that leftover Turkey is just as good as the T Day serving.

You're right, leftover turkey seems to always taste better the second day. Problem for us is: What to do with the rest of it after we're tired of leftovers.... Oh well, that's something to be very thankful for. So many don't ever have enough to even know what leftovers are.... We're so very fortunate !!!

Anyway, Back to furnace operation: Here is a link to the Suburban RV Furnace Service Manual. In it, you'll find a "sequence of operation" which will describe in detail exactly what's happening inside an RV furnace when the thermostat calls for heat. Pages 23, 24, 25, and 26 describe the different furnace technologies and how they operate. Some very interesting stuff, and a basic understanding of this manual will give most owners a new perspective on "that danged noisemaker".....

http://www.bdub.net/manuals/Suburban_Service_Manual.pdf

ADDED: The troubleshooting steps in this manual are the most complete I've ever found. They will help most anyone identify and solve furnace malfunctions, but unless you're familiar with the sequence of operations, the troubleshooting steps won't make a lot of sense to most people.

xrated · 11-26-2016, 07:12 AM

One more post that's just a little off topic......Leftover Turkey.......or pretty much anything else that is freezable. Food Saver! We've had one for the last 4 or 5 years and my wife makes use of it regularly. We've put food items in the Food Save vacuum sealer and marked the date, only to thaw something out and use it two years later...although most stuff doesn't get kept that long. They're as handy as a pocket on a shirt, and saves a lot of money by not throwing away leftovers.

**chuckster57** · 11-26-2016, 07:43 AM

On our second food saver...wore out the first one!!

**sourdough** · 11-26-2016, 09:49 AM

On our 2nd as well and bought both kids one. Love the thing!

Lawdogs · 11-26-2016, 10:54 AM

Was having same issue with our new trailer. Back to the dealership for warranty repair. Was first told that they were going to replace the furnace fan motor. When I went to pick it up after repair, they told me foreign material was keeping the fan from turning. I.E....there were loose sheet metals screws bouncing around the squirrel cage area and one got lodged.

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