blower fan relay?


  #1  
Old 06-05-02, 02:45 PM
jake3412
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blower fan relay?

I have a Carrier plus 90 furnace.My problem is , when the furnace heats the house and the thermostat shuts off,the blower runs until i shut it off at the breaker.After about 5 or 10 minutes i can turn the breaker on and it stays off until it cycles again. any help would be great!
 
  #2  
Old 06-05-02, 06:38 PM
PHnd
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That doesn't have a fan relay in the general sense. Its built into the main circuit board. It tough to diagnose from here. The only thing I can think of would be a bad module (circuit board) where the delay timer is not functioning properly or possibly, what I would call a sneak circuit. Which is where you would have something like a pinched wire in the control circuit that is not a tight solid connection (hard to detect) but just enough to leak a small amount of voltage that will hold the heating fan relay in but not enough voltage to pick it up once the power is turned off and back on. One possible clue to the circuit board timer being bad might be an abnormally long on delay. That furnace has about a 45 second on delay after the burner starts. If it seems long or irratic it could be bad which is effecting the off delay also. If that seems ok try going to the a/c if you have and at the furnace, inspect and tighten all the low voltage wires. If any are pinched clean them up. If any wires are pinched they could collapse the insulation just enough to leak voltage. Next pull the t-stat off the wall and look at the wires inside to see if they are criscrossed doing the same thing. Run the unit again and see if anything changes. If not while its running in the failed mode, pull the t-stat and remove the "G" wire and see if the fan stops. You should actually do that first. That will tell you if something is leaking through the stat fan circuit. Either way ifs a good idea to check the wiring for tightness. If you have an electronic stat its possible it has a leak somewhere in the circuitry bleeding through the fan circuit. At the moment, other than this, I'm at a loss.
 
  #3  
Old 06-06-02, 04:07 AM
ServiceGrunt
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Sounds like it might be going off on the high limit. If this unit has a red flashing light on the when this condition exists, count the number of times it flashes ( 3 flashes, pause, 3 flashes = code 33 ect.) . Then look on the backside of your furnace door to see what that code means. The red light will be in the blower compartment sometimes visible thru a sight glass or a round plug that you can pull off the blower door to see the light. If it is showing a open limit code, check your filter and your a-coil for obstuctions.
 
 

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