Heat Pump Problem

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  #1  
Old 11-24-02, 03:31 PM
Jay and Sandy
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Question heat pump auxilliary heat sometimes won't switch off/on:bad relay?

Our problem is that at times, our aux heat fan on our furnace will not kick off. We can hear the furnace clicking,like its attempting to switch off, but the aux heat light on the thermostat just blinks off and on. Other times, aux heat doesn't come on when it should and the fan blows out cold air. We know the reversing function of our furnace/heat pump doesn't always work, because sometimes in the winter, the heat pump freezes up on the outside and we have to turn the A/C on for a bit to melt all the ice build-up. Last week, for the frist time that we've ever noticed, we took the panel off the furnace front, and there was ice on the inside coils. Turning the A/C on melted that ice right away, but what could be causing this? We were thinking a bad relay switch. But when my husband took the panel off, he couldn't find the relay to even check it. We have an Arcoaire furnace model #BYMB024G from 1987-ish. Or would the problem be with the thermostat? My husband looked in home imporvement stores at new thermostats and couldn't even find any with aux heat modes on them.

Thanks for any help you could send our way! We'd like to get a few more years out of this system!
 
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  #2  
Old 11-25-02, 02:24 PM
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Well, the "reversing function" is actually called defrost in heating mode. The ice and flikering light would indicate a faulty defrost board in the unit.

The ice in the "furnace" call it the air handler in heating would lead me to look for a shortage of refrigerant. If the system is short the gas could flash at the evaporator coil and freeze the coil.
 
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Old 11-25-02, 04:38 PM
Jay and Sandy
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heat pump aux heat and freeze up problems

Is the defrost board in the outside unit? When these go bad are they typically replaced or repaired and what is the approximate $$?
 
  #4  
Old 11-25-02, 04:40 PM
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defrost board

if you are SURE it is bad get one at www.heatcoolparts.com, typically $250 to $450 installed. your cost @$100
 
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Old 11-25-02, 04:51 PM
Jay and Sandy
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defrost board

How difficult are they to install? Is it located in the outside unit or in the air handler inside the house?
 
  #6  
Old 11-25-02, 04:56 PM
Jay and Sandy
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defrost board

Also, this only happens every once in awhile it seems. This is the first time we have had ice in the air handler inside the house. It freezes up frequently outside however in real cold weather. Might it be just a bad relay somewhere or fuse?
 
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Old 11-25-02, 05:23 PM
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defrost board

located in the outside unit. BE SURE THIS IS BAD BEFORE REPLACING if not, you would have been cheaper to call a pro. by the way, one possible cause of unit sticking in defrost in refrigerant undercharge. may want a tech to look at it, you can always benefit from a professional opinion, and fix it yourself.
 
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Old 11-26-02, 09:57 AM
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The board is outside and changing it is a matter of shuting off power and changing wires from on board to another, one at a time. If you change the board also get a new defrost sensor which is attached to the outside coil and plugs into the board with two wires.
 
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