A/C Fan problem


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Old 06-13-08, 05:33 AM
J
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A/C Fan problem

3 Coleman, electric heat and air. Get home to find the compressor running, not the air. Turn the unit off, wait an hour and it works fine. Does it again later on the the down time intervals start increasing. I took a spare thermostat on installed it on the base on the wall. Unit immediately started working fine and did so for two days, then started not working in increasingly shorter intervals. Removed the thermostat base, bought a new digital thermostat. Unit worked fine for two days, now back to having problems (compressor running, fan not,). I have decided it must be a relay, or the high speed on the fan kicking out. But why does the thermostat change, clear up the problem for a few days.

Thanks,

John
 
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Old 06-13-08, 05:52 AM
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Which fan is not working?
The one outdoors next to the compresor? or the one indoors that moves the air thru the house?
 
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Old 06-13-08, 05:55 AM
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Originally Posted by pflor
Which fan is not working?
The one outdoors next to the compresor? or the one indoors that moves the air thru the house?
the inside blower.
 
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Old 06-13-08, 05:59 AM
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By the way the first time it happened I found that the switch in the thermostat for heat/gas or heat/ electric was set wrong. I set it to heat electric and that cleared it up for about two days, then the problems started again.
 
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Old 06-13-08, 06:12 AM
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The fact that the unit seems to work for some time after switching the t-stats does not really have an explanation, it's just a coincidence.

Check the indoor blower: the condition of the capacitor and the running amps of the motor. Make sure the control wires feeding 24V to the fan relay are nice and tight.

How old is this unit?
 
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Old 06-13-08, 07:12 AM
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The inside unit was installed in 2000.
 
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Old 06-13-08, 08:08 AM
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Thank you very much for your input. I will check both of those items. I didn't realize that if the fan inside would not run, that the compressor outside would continue to run, attempting to reach the temperature set on the thermostat.
 
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Old 06-13-08, 08:31 AM
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Originally Posted by jluke
I didn't realize that if the fan inside would not run, that the compressor outside would continue to run, attempting to reach the temperature set on the thermostat.
Ohhh yeah!
You bet the outdoor unit will continue to run, something which is absolutely not good for the compressor...besides, you'll never reach the thermostat setpoint under those conditions, the outdoor unit will work itself to death (literally speaking!)
 
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Old 06-13-08, 09:10 AM
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you will probably end up replacing the blower motor and capacitor but check the basics first electrical connections and voltage supply to the relay or control board. Are there any other symptoms that might help with the diagnosis such as noisier than usual blower etc?
 
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Old 06-13-08, 09:38 AM
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No other symptoms. The blower seems to work fine, ver quiet. As far as I can tell, it has never shut off in a cycle, will simply not start on occasion. Sure appreciate the input, I will let you know the outcome. I am going to start by checking the voltages and connections and will replace the start capacitor, just in case.
 
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Old 06-13-08, 09:53 AM
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if you keep a close eye on the unit you might want to do that capacitor changeout first and then watch, but keep in mind that the compressor can be damaged by liquid slugging if this keeps happening. What you may want to do is order yourself a air flow switch that proves airflow before your compressor is allowed to start, now of course you will spend probably more than simply replacing the blower motor and capacitor but think of all the fun you will have messing with it.
 
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Old 06-26-08, 11:34 AM
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Thanks for all the help. The motor does not have a start capacitor, just a run one, which I replaced. The problem turned out to be the sequencer, which seems to be like a combo relay/timer. It turns the fan on x seconds after the compressor cuts on and shuts it off x seconds after the compressor cuts off. $32 part, easy replacement.
 
 

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