RV Repair/Suburban SF-30 furnace losing power from converter
Need help. I canít figure this one out. Have a Suburban SF-35 furnace. Worked fine last winter. However the first time I turned it on this winter this is whatís happening:
The furnace comes on fine and does everything it is suppose to do, blower sounds good and heats up fine but after a couple of minutes before it has reached the stat cutoff temp. it shuts down because my converter shuts down the voltage to it. I hooked my multi meter to the converter output and Iím getting a constant 13.8 volts up to the point it cuts off. It does not draw down.It does not throw a breaker or blow a fuse. Of course when this happens, I lose my lights and anything else running on the converter. After about 30 secs.or a minute the converter will cut back on and the furnace will start back up for awhile and do the same thing. The converter works fine when the furnace is not operating. I donít know if the furnace has a problem causing my converter to shut down due to overheating or I have a problem with the converter. It is confusing since it maintains a constant 13.8 volts up until the time it shuts off. The converter fan is blowing as it should. I took the furnace out and checked all of the connections and blew the unit out with air and found no obstuctions. I couldnít figure out how to take the furnace apart to get into the furnace chamber to check for any obstrutions. This is so frustrating. Please help.
Your furnace is probably drawing too much current. that is different that voltage. If you draw too much current (amps) then the converter will shut down to protect it self. Then when it cools enough the overloads will reset, and come back on. There are a couple of reasons for this to happen.
1. the motor for the furnace is going bad. It is burning out or shorting slightly. You can test this with a dvom set on ohms and testing the motor leads, disconnected of course. test each of them to ground...you should see OL, or open. Then between themselves. You should see something low, like .1 ohms or so. If you see something high, too much resistance and too many amps are being drawn.
2. dirty filter causing the fan to work harder. Maybe a build up from mouse or bugs at the intake side of the fan.