Blower on furnace hums and doesn't start

I am having problems with one of my two furnaces. When the thermostat kicks in, the furnace will light, but the fan won't kick in. Then the furnace shuts down. If I turn off the heat (i.e. not on heat or cool), and turn the fan to "on", it just hums (the other furnace works fine and the fan will run). There is a solenoid that clicks, then the humming. The fan itself turns effortlessly.
Do you think this could be a problem with the capacitor, solenoid or transformer?
Also, I have been having another problem (probably unrelated?) once a year every winter when I first start the furnace. The fan doesn't want to kick in but I didn't notice any humming - this appeared to have something to do with that timer-like dial (is it a temperature limit switch?). Two taps with the end of a screwdriver and I'm usually OK for the year.
Any ideas on either problem? Thanks.
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Too many variables to diagnose by remote control like does the blower (fan) motor have a start cap , run cap , both or neither (blower motors can be any of these). Could be a cap problem , relay problem , open start winding or none of these -again depending on your equipment. The best bet is call in an HVAC tech to take a look and I hope your not hitting the fan limit switch with that hammer as it is also a safety device :-( .
Henry
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On 23 Nov 2003 09:33:42 -0800, snipped-for-privacy@mail.com (Mark) wrote:

I'd replace the capacitor and see if that fixes it. They are cheap enough to take the gamble. If that dont fix it, the fan motor is probably shot. Take out the whole blower and take it to a motor repair shop and have the motor tested and repaired or replaced. Blower removal should not be that difficult. Probably 4 bolts, and the wires. Of course shut off the power @ the breaker when you remove the wires.
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Beat it bozo, so skulk back to your regular NG bonehead
(Mark) wrote:

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Hi, First, when it's humming trying to go, give a gentle push and see what happens. If it runs, capacitor or the cetrifugal contacts inside the motor housing needs cleaning. Tony
profft wrote:

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Tony, You aren't too bright......telling somebody to stick their fingers into a blower wheel with the motor energized???? I hope you got real good liability insurance when "Lefty" comes knocking on your door.
--
Steve @ Noon-Air Heating and A/C
snipped-for-privacy@comcast.net
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This is Turtle.
Would you leave out bad bearing for some reason?
TURTLE
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If you live in or near a decent size town, and really know how to work electricity safely....
Lock it out, mark both ends of all connections, pull the fan motor ( take fan off) and the capacitor and take them to your local electric motor rewinding shop. Look for sign that says "counter" in some form. Wait in line patiently, be nice and offer the guy a soda or coffee.They will be able to quickly test both (because they have to disprove 'returns') and sell you the right one wholesale.
The small motors are not rebuilt, but replaced, should be $35 (often) to $75.
It's not rocket science, don't get killed.
Tim S.
(Mark) wrote:

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this is Turtle.
Mark you need to oil the motor before it eats the bearing up in it and you have to change it. If you have been oiling it, Change the motor out and the capasitor. Don't mess with repairing a motor for all your asking for is trouble.
TURTLE
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it hums......................because it doesn't know the words
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Mark, Maybe yeah. Maybe no. I don't know. I forget. But slip me a $50 bill and my memory might get better.
Jabs
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volts500 Spilled my beer when they jumped on the table and proclaimed

Psst. Every furnace I have seen for the last 15 years had a direct drive fan, meaning no belt...
NOI
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Wrong thread man..:)

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This is Turtle
He had me for a minute here and was gazzing at the screen. I can remember changing a bunch of belts on hvac system [ new stuff ] but he said they don't have them. i had to stop and try to remember where I've been to check on this statement. Awwwwwwwwwwwwww Some of them there new hvac system do have belts. Hey thank you for reminding me I'm suppost to change the belts on the First Baptist church in Pitken , Louisiana for I was suppose to change them last Friday.
TURTLE
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CBHvac Spilled my beer when they jumped on the table and proclaimed

Again? Gawd dammit! I'm going back to aacf. <G>
NOI
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