furnace fuse blowing

Lots of possibilities but the most likely is a frozen motor. See if you can manually spin the fan. If not then the motor is frozen.

jimmypsp700 wrote:
Hey guys.

I have a question I'm sure someone has the answer to and many of you have probably experienced too.

Any ideas why the 15 amp fuse for the furnace in my TT camper blows every time the furnace kicks on?

Its a 1994 Sierra 32' TT with the original Suburban SF series furnace.

thanks in advance for your help.

Jim

Pretty simple, you have a short or fan motor bearing are shot.

Furnace needs some TLC, but please do not try a higher current fuse, doing so will result in your trailer being a lot hotter than you want by over heating the wiring..

The simple answer is that your furnace is pulling more than 15 amps. The trick is determining why which will require more sleuthing. Under normal conditions the furnace will pull 7 to 9 amps.

You've received some good tips on where to look.

Thanks guys, great information.

The blower was just replaced last year as the bearings were shot, hopefully not that or motor but I doubt there's a short. Checked the wiring also tried a 20 amp fuse which proceeded to blow immediately which apparently is probably a good thing according to previous posts.

Thanks again guys, I will check back later when I get a chance to look into and possibly fix that issue.

Jim

You have a short or a frozen motor.

jimmypsp700 wrote:
Thanks guys, great information.

The blower was just replaced last year as the bearings were shot, hopefully not that or motor but I doubt there's a short. Checked the wiring also tried a 20 amp fuse which proceeded to blow immediately which apparently is probably a good thing according to previous posts.

Thanks again guys, I will check back later when I get a chance to look into and possibly fix that issue.

Jim

jimmypsp700 wrote:
Thanks guys, great information.

The blower was just replaced last year as the bearings were shot, hopefully not that or motor but I doubt there's a short. Checked the wiring also tried a 20 amp fuse which proceeded to blow immediately which apparently is probably a good thing according to previous posts.

Thanks again guys, I will check back later when I get a chance to look into and possibly fix that issue.

Jim

First rule of thumb for fuses.. Always fuse to the size of the WIRE..

A 15A fuse would typically mean that the wire is 14 ga which can SAFELY handle 15A.. 14Ga wire is PROTECTED from BURNING YOUR TRAILER DOWN TO THE GROUND by that 15A fuse!

You HAVE VIOLATED the fusing requirements by using a 20A fuse..

PLEASE, NEVER substitute a larger fuse!

With a 20A fuse blowing you HAVE A SHORT CIRCUIT SOMEWHERE.

What I would do is temporarily run completely separate 12V (pos and neg) from the battery to the furnace. use 14 ga wire and for goodness sake, FUSE the blasted thing at no more than 15A!!!!

If fuse blows on the temporary wiring then you have a SHORT IN THE FURNACE.

If fuse does not blow then you have a short in the wiring feeding the furnace..

You didn't by chance connect your battery up incorrectly?

Switching the polarity of the battery CAN blow the reverse polarity protection diodes which may be present on the furnace control board..

Other possibility is the furnace control board is just plain shot..

To figure that out you would have to disconnect the fan motor from the control board and connect the fan motor directly to 12V.. And once again MAKE SURE you ARE fusing the wire feeding the fan motor!

Check for squirrells having eaten insulation off the wires somewhere. They'll eat the insulation off down to the copper. The wires lay accross each other and there's your short. Ask me how i know.

Ralph

jimmypsp700 wrote:

...I doubt there's a short...tried a 20 amp fuse which proceeded to blow immediately....

When a fuse opens immediately it most likely is the result of a dead short. Either a wire or the motor itself is providing a direct path to ground.

In case you aren't aware, full 12vdc power goes through the thermostat, don't forget to look there.

I know better about the fuses now thanks for all the great info guys.

I did check the external wires they seem to be fine going to the furnace and the connections.
I did not think of the thermostat affecting it, at least blowing the fuse. Sounds like most likely it is the motor but we'll find out soon enough...

Just yesterday I discovered a 110V supply line that was stripped bare for a 4 inch section. How it didn't short...I dunno.