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I have a central heating system that was installed in this house in 2006. Tonight, while I was taking a nap my wife said that she suddenly heard a loud whine/whistle sound that slowly lowered in pitch and loudness. As it lowered the heated air that was coming from the vents slowed down with it. At this point she turned off the heater at the thermostat and woke me up. The entire house smelled very strongly of an acrid burning smell (like an electrical fire).

The smell has gone away now about an hour later, but in that time I checked the basement where the heating unit is and it didn't smell at all.

When I looked at the heating unit, it had 2 breakers and neither were tripped. I opened the side panel and manually moved the blower and it turned fine. Then about 20 minutes after it happened I turned the heat back on and the blower started, but very slowly and after about 60 seconds slowed itself down again. If you manually push the blower while it is on, it will spin for a few seconds then slow. You can hear that it's trying to move itself.

If you flip the left breaker only to off it completely stops and makes no noise. If you flip the right breaker only to off nothing changes.

When it comes to home repair I am as useless as a noodle in a tornado. Also, cannot afford a repairman at this point...and it's below freezing outside. :(

BIG EDIT
Took some pictures for my own sake and for explanations sake:
First, here is the whole picture:
alt text

Here is the capacitor (the only one I can find anywhere):
alt text

When I shorted the capacitor and then tested it for voltage I get nothing at all. I have no idea if that's normal but I only have a Voltage meter not a Multimeter.

Here are the wires that went into the Capacitor:
alt text The 2 purple ones went to the same terminal (top) and the orange went to the other one. The thick purple and the orange ones then went to the back of the blower motor, while the small purple one traveled up to this thingy:
alt text

I have no idea what it is or what it does.

So where do I go from here? There are so many wires that I can't make sense of them all and I have no idea what the "thingy" is or if it's the problem. Any help is much appreciated.
P.S. --> When I shorted the capacitor with a screwdriver to test it, nothing happened at all. No small spark or anything. Is that normal?

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    The "thingy" appears to be a transformer.
    – James Van Huis
    Jan 6, 2011 at 22:17
  • Just curious... Did you ever resolve this issue?
    – James Van Huis
    Feb 15, 2011 at 18:56
  • I did resolve it, the blower motor was fried. I found another motor at a relative cheap price but did find out that my furnace was installed with a stupidly rare blower that no longer has a motor in production. I got the last one available in the U.S...so if it fails I need to get a new furnace installed.
    – James P. Wright
    Feb 16, 2011 at 20:10
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    A key thing I didn't know at the time. The blower should spin freely if the motor works. If the motor is blown, and you spin the blower blades and they don't keep going for a while then your motor is bad. I didn't realize that or I could have solved the issue quite a bit faster. Still, thanks to everyone that tried helping!
    – James P. Wright
    Feb 16, 2011 at 20:11

2 Answers 2

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Sounds like your blower may be done but I am not really sure. One thing to try is to call your Gas or Electric company and see if you have a service plan. Some utility companies include a service plan charge on your monthly bill (and you might not even know about it) and it includes 24 hour service.

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  • Yep. My gut says the blower motor is fried. This is something that in theory one could replace, if they could find the right part. But if they don't know anything at all, an admittedly very unhandy home repairman also might electrocute themselves doing it, or fry the electronics in said furnace.
    – user558
    Jan 5, 2011 at 12:23
  • My very similar furnace experienced a motor failure this fall. I tried replacing the capacitor, but that didn't help. I was able to source a motor locally for about $110 and installed it with little trouble. If you're handy with tools, I wouldn't be afraid to tackle the job.
    – isherwood
    Dec 16, 2016 at 15:52
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This may be as simple as the "start" or "run" capacitor going south (because the motor starts but dies afterwards, I suspect that the run capacitor is blown).

If you are comfortable digging around in the control box for the furnace, then you should be able to find 1 or 2 large-ish capacitors. If you have a multimeter, you can test them against the specs that are listed on the casing. They should be within 10% of the nominal value. If you don't have a meter, then you can still give them a physical inspection. Occasionally, they will bulge or leak or give some other indication that they have failed.

If you find that either of them has failed, then you should be able to find a capacitor with similar specs online (or at a local HVAC supply). It should not run you more than about $15.

Here is a link with additional info and a short video explaining more about the capacitors.

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  • I actually found that exact site already and just need to get multimeter somewhere. I have a Voltage Tester, is that the same thing or a more simplified version?
    – James P. Wright
    Jan 6, 2011 at 20:06
  • If you are talking about a non-contact voltage tester, then it is not the same thing. You will want a meter which will measure capacitance (for example, amazon.com/Sinometer-DT9205-8-Function-32-Range-Multimeter/dp/…)
    – James Van Huis
    Jan 6, 2011 at 20:22
  • Open up the cover and take a look at the capacitors. You may be able to see if they are bulging or leaking. If they are, you don't need the meter (at least not right now).
    – James Van Huis
    Jan 6, 2011 at 20:25
  • What I have is a yellow box with a red and black pen-like devices on wires with metal points at the tip. It is analog and just shows how many volts is flowing. I am in the process of uploading some pictures and editing the original question to see if I can get any more help on this.
    – James P. Wright
    Jan 6, 2011 at 20:30
  • Given the details in your edit, if I were in your situation, I would just replace the capacitor. You should be able to find a replacement locally, and it should only cost $10 or $15.
    – James Van Huis
    Jan 6, 2011 at 22:15

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