Furnace problems HELP

[jsb5717]

The resettable fuses are glitchy and trip prematurely. Just try a standard blue 15a fuse and see what happens.

 

[JRTJH]

I believe it is black. I’m not home right now. Why should it be replaced? So I know when it’s blowing a fuse? Only a short would blow the fuse correct? Limit switch will trip and valve will close in other scenarios of malfunction.

The black fuse is really a "thermal auto reset circuit breaker". What happens as that "black fuse" gets old or is used in a circuit "very close to the max capacity" is that the spring/reset mechanism gets weak and it starts tripping lower and lower. So, a 15 amp auto reset "black fuse" may start out tripping at 15.5 amps, and after a year or so, begin tripping at 14 amps, then after doing that repeatedly, start tripping at 13 amps, then 12 amps, then .....

So, with use, it just gets weaker and weaker until it affects the operation of the product it's intended to protect.

Replacing it with a simple "one time use thermal fuse" eliminates that condition.

There was a recall by a furnace company (can't remember if it was Atwood or Suburban or ????) instructing repair centers to replace the "auto reset fuse" with a conventional fuse of appropriate amperage.

 

[jsb5717]

Any new news here? Just wondering if a new fuse helped.

 

[ChaseM]

Fuse did not help, it actually blew a regular 15amp once which doesn’t make sense to me as I’ve confirmed nothing is short circuiting and it randomly turns off. My best guess is the blower motor, gonna replace that and maybe the igniter then after that I’ll pretty much have refurbished the whole unit so if it doesn’t work I’m screwed lol

 

[JRTJH]

Fuse did not help, it actually blew a regular 15amp once which doesn’t make sense to me as I’ve confirmed nothing is short circuiting and it randomly turns off. My best guess is the blower motor, gonna replace that and maybe the igniter then after that I’ll pretty much have refurbished the whole unit so if it doesn’t work I’m screwed lol

If it blew a 15 amp fuse and you've checked the wiring to be sure it's not shorted or corroded along the lines to the furnace, I'd recommend you measure the "line voltage when the furnace blower fan first comes on line"... Remember that as voltage decreases, amperage increases. So, if the fan motor is "slow to start, has a bad bearing, is dirty and not spinning freely or has bad brushes" or if you've got a corroded connection somewhere from the battery to the furnace (through the fuse panel) then you may have a significant voltage drop. A voltage drop that is enough to blow the 15 amp fuse is significant enough to trigger the furnace to shut down or not "spin up fast enough to confirm correct sequence of operation" and put the furnace in "lockout mode'....

I also suspect you may have a bad motor based on blowing the fuse, but I'd hate to see you replace the motor and have the same condition and same failures. I'd confirm the voltage as the thermostat calls for furnace ignition and see if it remains at 13.6VDC (on shore power) or 12.6VDC (on battery power)...

 

[ChaseM]

If it blew a 15 amp fuse and you've checked the wiring to be sure it's not shorted or corroded along the lines to the furnace, I'd recommend you measure the "line voltage when the furnace blower fan first comes on line"... Remember that as voltage decreases, amperage increases. So, if the fan motor is "slow to start, has a bad bearing, is dirty and not spinning freely or has bad brushes" or if you've got a corroded connection somewhere from the battery to the furnace (through the fuse panel) then you may have a significant voltage drop. A voltage drop that is enough to blow the 15 amp fuse is significant enough to trigger the furnace to shut down or not "spin up fast enough to confirm correct sequence of operation" and put the furnace in "lockout mode'....

I also suspect you may have a bad motor based on blowing the fuse, but I'd hate to see you replace the motor and have the same condition and same failures. I'd confirm the voltage as the thermostat calls for furnace ignition and see if it remains at 13.6VDC (on shore power) or 12.6VDC (on battery power)...

Okay, check at the blower leads them selves and confirm voltage after calling for heat from the thermostat? Thank you

 

[JRTJH]

Okay, check at the blower leads them selves and confirm voltage after calling for heat from the thermostat? Thank you

Yes, Check for a voltage drop WHILE THE STARTUP PROCESS BEGINS...

I'd first check at the furnace connection to the trailer wiring (to isolate the furnace) then if there IS a voltage drop, I'd then do the same test AT THE FUSE to see if the issue is "closer to the battery" vs "inside the furnace"...

If the voltage drop is present "only at the furnace" then the problem is between the fuse panel and the furnace motor. If the voltage drop is present at the fuse panel, then the problem extends to the battery/converter and is not isolated to the furnace wiring from the fuse.