Trane AC inside fan not turning on


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Old 06-30-09, 12:52 PM
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Trane AC inside fan not turning on

Noticed it was rather hot (85F) in the house the other day so I selected a lower temp on the stat. Outside condenser fan cranked immediately but no inside fan.. SO I checked the circuit breakers which were all fine(there have been a lot of electrical storms lately in So. FL), but recycled them anyway. Still no go with inside fan, so I decide to turn system off at stat and do some research and then take a flashlight up in the attic to look at the compressor and fan unit.

Before I make it to the attic, all of the sudden there is cold air blowing out of the vents, but the thermostat is still in the OFF position????Air runs normal the rest of the evening cooling beautifully. I know it doesn't make any sense..but nevertheless, I matched the switch with the running condition.

The next day it gets hot outside again and the inside fan again isn't turning on?? Outside fine again running like a champ. This time I make it to the attic and find that with the A/C stat selected to on that the compressor begins to hum and copper line begins to cool nicely. Shut off power now, remove access panel to fan and compressor. No burnt smells and all appears normal. Found 5 amp fuse and it checked good using a meter.

Turn power back on and try to start fan with a stick. No go but it does turn freely. Shut power back off and remove capacitor and have tested by an A/C guy at the parts store before buying a replacement. It checks good(and is not bulging either), so I reinstall it. After several attempts, still no go and the motor and capacitor are not even getting hot.

The whole system(trane 12 seer 4ton heat and ac unit) was installed new 4 yrs ago. I next inspected the LuxPro thermostat which seems to check good. Batteries are good and no signs of burning. I get a meter jump while touching probes on back while cycling the fan and power switches from ON to AUTO and from OFF to COOL and HEAT respectively.

Any idea from you guys in the know? Sorry for long dissertation. I hope that I have given enough info. If the motor was bad, wouldn't I be able to tell by a smell and it heating up from it trying to run? Kinda sounds like a power supply issue to me but I don't know what else to check??
 
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Old 06-30-09, 01:17 PM
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Cold motor means it's not getting power. Look for a G and a C [might be B] terminal in the air handler where the cable comes frm the thermostat. Next time it happens check for 24 volts from G to C. If no, the problem is outside the air handler. If yes, the problem is inside the air handler- bad fan relay. loose connection, etc.
 
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Old 06-30-09, 09:49 PM
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Thumbs up

Originally Posted by daddyjohn
Cold motor means it's not getting power. Look for a G and a C [might be B] terminal in the air handler where the cable comes frm the thermostat. Next time it happens check for 24 volts from G to C. If no, the problem is outside the air handler. If yes, the problem is inside the air handler- bad fan relay. loose connection, etc.
Thanks John,

I studied the wiring diagram, found the wires coming in from the Theremostat. Could not figure out what G, C and B terminals could be honestly although I think you may have meant the green and red wires that went from the Thermostat to the Fan Delay Relay etc. All of the other wires(4 or 5 in all) from the thermostat were connected to those darn float switches(a weak point in my opinion though I know they are needed in some fashion).I did however check and snugg every connection on the handler including the float switches in the drain pan. I turned the power back on and voila the fan fired right up. Obviously, there is a bad connection somewhere in the mess. I suspect it may have to do with those float switches which seem rather flimsy and ripe for errors.

Blowing nice and cold now. Thanks for your advice. It would have been a shame to call someone out for a bad connection.

Many Thanks Friend.
 
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Old 07-01-09, 04:48 AM
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you're welcome sir. I agree with you, it was probably the float switch, they're real flimsy.
 
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Old 07-04-09, 01:02 PM
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Happy Fourth of July to all!! It is a hot one at my house. There has been a new development since our last exchange. I was out town and the fan apparently only worked that one time. As it turns out, when the inside fan shut off, it did not come back on. I was unable to get it to come back on again until today when I bypassed the Fan Delay Relay. With that temporarily bypassed(using a short jumper wire, it again cools nicely.

Question is this. Today is the 4th of July so I can't get a replacement part until Monday at the earliest. Is there a problem with me leaving the fan in the ON position for a few days until I can get a new Relay? The relay will effectively not be called into use in this configuration it seems? Am I risking damage to any of the other components by bypassing this relay?

The Fan Delay Relay is permanently mounted on a small circuit board that has about 4 or 5 various wires connected to it. It seems I will have to replace that entire circuit board. I am thinking one of the electrical storms must have killed the relay.

Thanks again gentleman.
 
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Old 07-04-09, 05:36 PM
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no problem with letting the fan run. Are you sure you had 24 volts going to the board's fan ciecuit from the thermostat? Can you post a pic of the board? We might be able to locate a generic. What kind of heat do you have?
 
 

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