SOLVED: furnace and AC fan won't turn on
SOLVED: see my response below for details. In short, replacing the thermostat fuse fixed the issue.
Hi All,
I have a 1997 Terry 30g RV with an Atwood 8531-III DCLP furnace and a Coleman 7300 air conditioner. I bought it from the original owner about 5 years ago. My current problem is that neither the furnace nor the AC fan will turn on (they worked fine last season). Even if I try running just the fan without AC, it doesn't turn on. I hear no noise whatsoever when I flip the switch on the thermostat (i.e. no humming like it's a stuck fan or something).
I checked the circuit breaker for the AC, and it's getting 118V. I checked the 15amp fuse for the furnace and it's fine (I tried replacing it twice just to be sure). However, I noticed that the furnace circuit itself is getting only 0.2V. I verified this with a multimeter by putting both red & black connectors into the slot where the 15A fuse goes. After I saw only 0.2V there, I temporarily switched the black wire going into the fuse slot with the one for the fridge (since the fuse for the fridge is also 15A). After switching the wires, I still saw 0.2V on the moved furnace circuit. So I know that my fuse panel isn't the problem, nor is the main circuit breaker for the AC. I also reset the GFI outlet in the bathroom just to make sure that's not related. Finally, I made sure the cranking battery was connected and charged.
So I'm pretty sure this is a grounding issue in the furnace circuit or one or more components along this circuit are just broken. My problem is that I can't tell where the black wire from the fuse panel ends up, so I'm a little lost at this point. Does it go directly to the control board for the furnace or somewhere else? I see no black wires when I open up ceiling port that goes to the wiring for the AC, and it's difficult to see the furnace wiring without taking the blower motor out.
Also, there's no indicator light for this thermostat, so I can't tell if it's even getting power. According to the manual, there's a 2A fuse for the thermostat somewhere, but I couldn't find it. However, I did notice that the red wire coming form the back of the thermostat was connected to a different (thinner) red wire running inside the wall using a plastic cap connector. So I'm wondering if the 2A fuse is just missing, and maybe my thermostat just got fried as a result.
Should my next step be to investigate the thermostat? I'm just not sure if that could possibly cause the furnace circuit to see only 0.2V instead of the expected 12V. I'm also wondering if there's a way to test the thermostat without cutting any wires going into it.
Thanks for reading and any advice.
Hi All,
I have a 1997 Terry 30g RV with an Atwood 8531-III DCLP furnace and a Coleman 7300 air conditioner. I bought it from the original owner about 5 years ago. My current problem is that neither the furnace nor the AC fan will turn on (they worked fine last season). Even if I try running just the fan without AC, it doesn't turn on. I hear no noise whatsoever when I flip the switch on the thermostat (i.e. no humming like it's a stuck fan or something).
I checked the circuit breaker for the AC, and it's getting 118V. I checked the 15amp fuse for the furnace and it's fine (I tried replacing it twice just to be sure). However, I noticed that the furnace circuit itself is getting only 0.2V. I verified this with a multimeter by putting both red & black connectors into the slot where the 15A fuse goes. After I saw only 0.2V there, I temporarily switched the black wire going into the fuse slot with the one for the fridge (since the fuse for the fridge is also 15A). After switching the wires, I still saw 0.2V on the moved furnace circuit. So I know that my fuse panel isn't the problem, nor is the main circuit breaker for the AC. I also reset the GFI outlet in the bathroom just to make sure that's not related. Finally, I made sure the cranking battery was connected and charged.
So I'm pretty sure this is a grounding issue in the furnace circuit or one or more components along this circuit are just broken. My problem is that I can't tell where the black wire from the fuse panel ends up, so I'm a little lost at this point. Does it go directly to the control board for the furnace or somewhere else? I see no black wires when I open up ceiling port that goes to the wiring for the AC, and it's difficult to see the furnace wiring without taking the blower motor out.
Also, there's no indicator light for this thermostat, so I can't tell if it's even getting power. According to the manual, there's a 2A fuse for the thermostat somewhere, but I couldn't find it. However, I did notice that the red wire coming form the back of the thermostat was connected to a different (thinner) red wire running inside the wall using a plastic cap connector. So I'm wondering if the 2A fuse is just missing, and maybe my thermostat just got fried as a result.
Should my next step be to investigate the thermostat? I'm just not sure if that could possibly cause the furnace circuit to see only 0.2V instead of the expected 12V. I'm also wondering if there's a way to test the thermostat without cutting any wires going into it.
Thanks for reading and any advice.
