Furnace Blower Issues

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Old 10-17-13, 06:37 AM
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Furnace Blower Issues

Furnace blower will not turn on... Here is a brief overview of what I have going on. I recently purchased a foreclosure home to rehab for my family. In doing this I spent all of my savings to buy the home so I have no money to put into it. To remedy this I am in the process to get a home lone so I can have some cash to fix the place up. But... the bank says that the home needs to be in sell able condition before they will give me the loan; ie. The furnace/AC must be operational, among other things. I replaced the thermostat with an updated digital one and made sure I had electric and gas running to the unit. I can get the burner to fire up just fine but the fan/ blower will not turn on. I switched the unit from fan auto to fan on and still nothing. You can hear the transformer inside of the furnace hum and I am getting 120vac to the fan when it I switch it to fan. I replaced the capacitor with a brand new one and still nothing. I jump the main power wire (white) over to one of the speed wires and the blower will start to turn but then the circuit breaker trips, I'm assuming there is a high pull on the system when first starting fan which is why breaker tripped. I am not very fimiliar with which color wire does what and which ones I should jump (that is why I am asking you guys). This is a rather old furnace, I beleave from the early 80's and is also a large unit as the house is 3,000 square feet (I think it is a 3/4hp blower motor). So this is a natural gas furnace with A/C. Like I said I am going to be fixing the house up and am going to be replacing the entire HVAC system but just need to get it operational for the time being, so it will be in saleable condition to get the loan. Can anyone help me and thanks in advance.
 
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Old 10-17-13, 11:14 AM
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You should take pictures of the controller circuit board and anything else you consider part of the blower control and post them to a site like flickr so experts can easily view them. Post brand and serial numbers from the furnace.

One thing an amateur can check is if the path from the from blower through the heat exchanger to the flue to the chimney is clear. You would do this by disassembling the flue and checking the chimney is clear with a mirror. Reassembling the flue can be a challenge I make pencil marks across the joint where the flue meets to make reassembly easier. If the path is blocked hot air will backup and trip a sensor that shuts the system down. The filter should be clean, and the path from the air intake in your house to the furnace filter shuold be clear. I regularly have to clean my chimney.

You might also make sure the blower wheel is clean. If it is not, it does not blow air fast enough to cool the furnace down and may cause the blower to overheat from spinning too fast and shutting down.

If this is an old furnace the electric motor may require oiling. If you know what oil ports look like they should be obvious on the motor. Only use oil ment for electric motors. If you can find a manual online it will probably tell you if the motor needs oil.

Other maintenance I have been able to do:
cleaning pilot light orifice
cleaning burners
putting metal tape over holes in duct work
insulating ducts.
 
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Old 10-17-13, 11:44 AM
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If you turn the fan wheel by hand, does it turn freely or is it stiff?
 
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Old 10-18-13, 07:47 AM
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Fan spins freely and smoothly with no restrictions. . Like I said it will start to turn when I jump the wires but will overload the breakers which causes them to trip. One thing I didn't mention, I'm assuming there was some kind of issue with the system when I purchaced the home because some of the wires were disconnected (from the capacitor, that is why I replaced it). I don't really know if I have the wires connected perfectly. From what I can see on line they look right (per color) but not sure. I have looked everywhere on the unit inside and out for some kind of a brand name and model # but I cannot find anything. There are a couple places on the unit that look as if there were tags there but are no longer there.
 
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