compressor comes on but not fan motor

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  #1  
Old 07-17-02, 11:12 PM
steve mcpherson
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compressor comes on but not fan motor

returned from a week vacation to find 3 electical things no longer working in my house,modem for computer which i replaced, t.v. which i can live without, and lastly my a/c isnt working.its a carrier 58rav,the compressor outside and fan above the compressor come on but the blower in the furnace doesnt come on, i checked the voltage at L1 and L2 and its at 115 where its suppose to be,however the voltage at sec1 and sec2 is 28.5 when its suppose to be 24 volts.does this mean the transformer is bad?or is the control center{circuit board}bad. thanks for any help. steve mcpherson
 
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  #2  
Old 07-18-02, 02:03 AM
lynn comstock
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Tests to try.

The control transformer is in the air handler or furnace. It is OK and the power supply is OK as well. (We know this because the outdoor unit is working OK.)

The fan motor or the fan relay may have failed. Turn on the HEAT. If the furnace fan does not come on, the fan motor is probably defective. (The heating mode bypasses the fan relay to power the fan by the temperature inside of the furnace.)
 
  #3  
Old 07-18-02, 03:56 AM
ServiceGrunt
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Sounds like lightning got into your stuff. The symtoms your furnace is having is all to familiar for Carrier circut boards. I had to replace a bunch of them with the last storm we had. Same symptoms as yours. As Lynn said, your transformer is OK. Homeowners insurance might cover your losses.
 
  #4  
Old 07-18-02, 07:31 AM
steve mcpherson
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i tried turning the heat on but still no fan. where to now?
 
  #5  
Old 07-18-02, 07:35 AM
steve mcpherson
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if it is the control board that is bad,is that something i can replace? it looks easy to exchange. approximate cost of the part?and labor cost if i dont do it myself?
 
  #6  
Old 07-18-02, 08:30 AM
lynn comstock
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Nest step.

If the fire did not come on when you called for heat, I'll bet on a control board. They are custom parts that most dealers could order for you. Replacing it should be simple enough...wire for wire. Cost could be $100 to $300 installed. Custom parts can be pricey and all circuit boards are custom.

If you replace any part on your furnace without the manufacturer's blessing on the new part, the manufacturer's liability for safety is sharply reduced. The furnace safety may be OK or compromised, no one knows unless it is tested. Don't become a test site.

If the fire came on and burned several minutes but the fan never came on, I would bet on the fan motor itself as defective.

Lightning will do the damage to multiple appliances. ServiceGrunt is right about that and his suggestion to call your homeowner's insurance agent.
 
  #7  
Old 07-18-02, 08:38 AM
steve mcpherson
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when i tried the heat,the burners did come on, just no fan.makes me think its the fan motor. is there a test for it? i also noticed the red LED light is not working on the control center,which makes me think its the control center. but luckily i got you to help figure out which is bad.thanks again.
 
  #8  
Old 07-21-02, 08:57 PM
lynn comstock
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Well I am inclined to believe that the circuit board is damaged.

First it is much easier to damage. I don't know the red LED and its function. A tech can measure voltages here and there to isolate the problem.

I suppose the fan relay is an integral part of the circuit board. You could measure the control voltage to the board (Common to Green should = 24v.) You could measure the motor voltage to see if the line voltage (115v) is reaching the leads to the motor. That is easy to say and not so easy to help you understand where to actually place the probes for a reading. If you are typical, you really need a tech to walk through it. Have him bring a board on the diagnostic call or he will end up making another trip.
 
  #9  
Old 07-28-02, 07:54 AM
steve mcpherson
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finally bought a new control center, installed it in 15 minutes,flipped the power on and everything works perfect. just wanted to say thanks for the help. steve
 
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