Suburban heater blows fuse

[infrared]

I have a 1996 Winnebago Brave (30 ft). Fan fuse had blown. When a new one is inserted, it blows before inserting with sparking. The A/C will not run. The heater won't run and when the fan setting on thermostat is selected it will not run. All of the units did run this summer. The furnace is a Suburban SF30? There is 12.68 volts where fuse is on control panel (#6)

[JohnRR]

:welcome:

[NeilV]

You have a short circuit or possible a bad fan motor. If you turn it to AC and replace the fuse does the AC now run?

The entire furnace is 12 volts while only the Thermostat is 12 volts on the AC.

[grtharris]

The furnace fan may be locked up do you have dirt dobbers were you park your motorhome?

[fletch460]

Had the same thing happen last week. Went to test unit and when I put it on heat, pop went the fuse. Pulled cover off furnace. You can see the fan blade, squirrl cage. Tried to turn it Couldnt. Looked inside and dirt dobber nest had cage dirt welded to shroud. Cleaned it and all good.

[infrared]

Originally Posted by grtharris

The furnace fan may be locked up do you have dirt dobbers were you park your motorhome?

The fan is free wheeling and no dirt dobbers. Thanks

[jesilvas]

Originally Posted by infrared

I have a 1996 Winnebago Brave (30 ft). Fan fuse had blown. When a new one is inserted, it blows before inserting with sparking. The A/C will not run. The heater won't run and when the fan setting on thermostat is selected it will not run. All of the units did run this summer. The furnace is a Suburban SF30? There is 12.68 volts where fuse is on control panel (#6)

When the new one is inserted and instantly blowing, is the t-stat set to OFF? I'm assuming it's a combo furnace/A/C t-stat?

[wa8yxm]

If the fan is free wheeling then the motor could be shorted out or the wires to it, Those are my first two guesses.

DISCONNECT the fan motor lkeads from teh control board and see if it still blows fuses.

if it does, Replace control board
If it does not replace motor

[infrared]

The thermostat is off for all functions. I disconnected the furnace (4 wire connector) and tried to replace the fuse, it sparked and blew before it could be replaced.

[jesilvas]

So you have a short before the connector. Has anything been taken out and put back in, new screws, staples, nails, ANY work?

[infrared]

I found a short at the furnace. The four wires to the furnace ran along the back of the furnace and made a 90 deg turn and then to the connector. At the corner of the furnace one of the wires was caught. I pulled it away and noticed bare wire and black around the exposed wire. I patched the wire and now everything works. There is sharp metal at the corner. Thanks for all of the suggestions

[JohnRR]

Thank you for the update.