Inside Fan won't turn off and outside condenser won't come on


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Old 08-02-09, 01:13 PM
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Inside Fan won't turn off and outside condenser won't come on

I have 2 units, 1 upstairs and 1 for the main level. This morning when I went downstairs I noticed it felt warm and the fan was running. I checked the outside condenser but it was not on. I thought it may be a problem with the thermostat because even when the thermostat was put on auto fan and the selection was turned to off instead of cool or heat, the fan still ran. I disconnected the thermostat from the wall, all wires disconnected, but the inside fan still ran.
I went into the utility room and turned off the switch which then turned off the air handler. I left it off for a little to maybe reset, but as soon as the switch is turned on the air handler comes on again, even with the thermostat wires still disconnected. I checked the breaker outside by the condenser and it appears to be normal. I switched it off and on again.
When the thermostat was still connected and the fan was running I could hear something click at the air handler when the switch was moved from auto to on, and when the other switch was moved from off to cool.
The units are the original Carrier units from when the house was built 20 years ago.
Any ideas? Thanks
 
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Old 08-02-09, 01:56 PM
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No pro..but they may be a while. I'd guess that you probably have a stuck relay in a control board somewhere. I say relay..but it could be an all solid state device (IC chip).

It sounds like something has just set itself in a certain condition..and any input makes no diff.

Post an actual model number and when the Pro's get here they may have some things for you to check. Can you use a meter and do you have one?
 
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Old 08-02-09, 02:08 PM
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Thanks for the response. The model is Carrier 58DHB/SSB. It's a combination gas furnace and A/C. And yes I do have a meter to use.
Thanks again
 
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Old 08-02-09, 03:56 PM
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OK- so you're saying that the indoor fan runs all the time AND the outdoor unit is not running? Since you have the themostat apart, what happens to the outdoor unit if you connect the red wire and the yellow wire together at the themostat?

update- I looked this model up, it came in downflow or horizantal configurations. Is the furnace in your attic?
 

Last edited by daddyjohn; 08-02-09 at 04:05 PM. Reason: update
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Old 08-02-09, 04:46 PM
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This is in my utility room off the garage, from the picture on the cover of the owner's manual it is the upflow unit. I don't have a yellow wire but the blue was attached to the Y connector on the thermostat so I connected them. Nothing. There wasn't even a small spark, so I put the meter on the red and white wires and I did get a 12 volt reading, so I do have low voltage power at the thermostat.
Thanks again for you help.
 
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Old 08-02-09, 06:32 PM
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12 volts is not enough voltage to operate the controls. Standard control voltage is 24 volts. Could be a weak transformer or a bad connection in the low voltage circuit. Some hvac equipment, including carrier, will run a continuous blower when the control voltage is lost. I'm not sure of the reasoning for it but I think it's meant to be an alert to a malfunction. Also, some circuit boards in carrier equipment have a diagnostic light that will flash a diagnostic code, this is where I would start.
 
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Old 08-04-09, 08:48 AM
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same problem as highpoint2

I am having the exact same problem as highpoint2, except I have a comfortmaker/epm24b15a1. When I put the meter on the red/white and red/blue wires I didn't get anything..no volts. I did this of course with the unit running. Any suggestions what the problem might be? I have read the circut board could be the problem..any way to test that? Highpoint, did you get it fixed?
thank you for any help!
 
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Old 08-04-09, 10:50 AM
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To get an accurate answer, using terminal designation, or location helps more than wire color. (maybe use both) Someone could easily help you short out your furnace using wire color. Like you said, you didn't have a yellow wire.
 
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Old 08-04-09, 11:03 AM
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The Y terminal has the blue wire. G=green wire Y=blue wire W=white wire rc=red wire.
I tested w/my meter the red and white...and red and blue
 
 

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