air handler fan dead - http://www.hvacmechanic.com/ Forums
Original message
| rasmusj2007
 |  "air handler fan dead"
, posted Sat 7 Jun 21:51  
Have a Trane XE1000. The fan for the airhandler quit and I replaced the capacitor as the motor was humming when turned on. This changed nothing, but while I was testing things I noticed that the motor was hot. Removed motor and took it to my shop and blew it out to cool it. Since there was no burned smell and it had impedance on all speeds I hooked it back up (outside the fan housing) the motor came back on on all speeds. After much sweat and foul language, I had it all back together in my 120 degree attic. Turned it back on and the thing just humms. Checked to make sure that fan turns and nothing is binding. I have always thought that AC motors were either good or bad like a lightbulb. Please help! This is too much for my simple mind.
never pay repair tech
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Replies:
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| burnerman
| "Re(1):air handler fan dead" , posted Sat 7 Jun 23:48
Well i hate your post never pay a service tech. Buttt had this happen once the voltage drop from panel box to unit droped to low to start the fan motor .Like you took it off sent it to be checked, nothing wrong opened panel box wire to one lead was loose. Try it. service tech not getting paid for this one
royboy
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| | rasmusj2007
| "Re(2):air handler fan dead" , posted Sun 8 Jun 12:32:
Looked for loose wire and could find none. Did try to help the fan by hand and found that it would start that way. The only way it would stay running was by running it on lowest speed setting. I still don't think that anything is wrong with the motor itself.
never pay repair tech
[this message was edited by rasmusj2007 on Sun 8 Jun 12:37] |
| | theduke03
| "Re(3):air handler fan dead" , posted Sun 8 Jun 13:34
I too would exhaust all options before condemning a motor that will run. You may have a bad blower relay causing a voltage drop to fan. Check voltage from relay terminal connected to blower and the blower L2 connection. Should be 230v+/- 10%.
You can also check for a v drop by putting your meter leads across the contacts. Locate on the wiring diagram which 2 terminals are the N.O. contacts for blower. With relay coil energized a good relay will read 0v across contacts. If more than 1v I would replace the relay.
"My dad was the most feared furnace fighter in Northern Indiana."
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| | rasmusj2007
| "Re(4):air handler fan dead" , posted Sun 8 Jun 14:50
Checked and had 0 V on relay. Have 240 V on motor between red (speed control) lead and black lead going into capacitor/motor. However, on otherside of capacitor (yellow lead going to motor) I have only 14.2 V between it and red lead. Is it indication of capacitance? From yellow to ground I have 120 V. Also, motor will not continue to run when wired for high speed.
never pay repair tech
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| | Houston204
| "Re(3):air handler fan dead" , posted Sun 8 Jun 13:32
If your motor is getting the proper voltage and the capacitor is good, but it will not run, replace it.
"Tip of the Day" Remember to remove power first.
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| | rasmusj2007
| "Re(4):air handler fan dead" , posted Sun 8 Jun 14:52
Can a motor run and be bad?
never pay repair tech
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| | theduke03
| "Re(5):air handler fan dead" , posted Sun 8 Jun 15:49
Well your voltage is good and the relay is good. That leaves either the motor or capacitor. A microfarad tester is the only foolproof way to test capacitor but here is a simple test you can do with ohmmeter to determine if cap has capacitance:
Shut off power to unit.
Short the terminals on the capacitor with a scewdriver to discharge it.
Remove wires from capacitor.
Set meter to ohms on highest scale.
Put meter leads on both terminals.
If OK then ohms should drop towards 0 then rise towards infinate/open. Then reverse leads and repeat and result should be same.
If ohms are low or high and dont move then capacitor is bad.
I would normally say a motor that runs is not bad but I have seen stranger things than that!
"My dad was the most feared furnace fighter in Northern Indiana."
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| | rasmusj2007
| "Re(6):air handler fan dead" , posted Sun 8 Jun 17:44
Using a Fluke 333 amp-clamp for a multimeter, have no setting for impedance range. out of several attempts, I did get a beep once indicating that it may have approached zero ohms. Display showed OL (infinite) no matter what. Wish I had an analog meter. This is a new 5mf (chinese) capacitor as this was the first thing that came to my simple mind to change. My next step will probably be to take the motor back out and put a couple of 303 bullets through it to make sure it's bad. What else can I do?
never pay repair tech
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| | theduke03
| "Re(7):air handler fan dead" , posted Sun 8 Jun 17:54
Well, I would call that inconclusive. You can either try another cap, or bust a cap into that motor like you said. Watch out for the ricochet.
"My dad was the most feared furnace fighter in Northern Indiana."
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| | rasmusj2007
| "Re(8):air handler fan dead" , posted Sun 8 Jun 18:06
Richochet, hmm... good point, with my luck I'd shoot myself in the foot. For a $5 capacitor I guess I could try another one. Would the next step be a motor in your opinion? Thanks for the help by the way.
never pay repair tech
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| | theduke03
| "Re(9):air handler fan dead" , posted Sun 8 Jun 18:42
"You'll shoot your eye out kid, Merry Christmas, ho ho ho"
But seriously, yes. If a new cap doesn't work then motor is shot. Like I said, I've seen stranger things.
"My dad was the most feared furnace fighter in Northern Indiana."
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