goodman furnace blower doesn't stay on

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  #1  
Old 01-13-18, 09:29 AM
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goodman furnace blower doesn't stay on

My goodman furnace (GMH80805CN) started acting up today. installed it last year and haven't had any problems until now. the heater will come on and the fan will come on for about 5 seconds-1 minute, or the fan wont come on at all. i left the heat on and fan on auto and it will just cycle. same problem with A/C. what could cause this?
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  #2  
Old 01-13-18, 09:35 AM
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So we can assume FAN ON works normally or not ??

It sounds like it could be a defective capacitor on the blower motor but unusual on a one year old furnace. I woud verify 120vac to the blower motor to eliminate a problem with the control board.
 
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Old 01-13-18, 09:39 AM
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when its switch "on" it has the same problem
 
  #4  
Old 01-13-18, 09:47 AM
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but i just turned on the fan and it seems to be running normal, been running for 5 minutes no problem. but a little after turn heat to on the fan quits
 
  #5  
Old 01-13-18, 10:05 AM
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cool works fine with the fan also, but about 30 sec after i switch it over to heat the fan stops.
 
  #6  
Old 01-13-18, 10:23 AM
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I'm trying to find out if your furnace has a variable speed ECM motor or a 3-4 speed PSC type motor. It's looking like the new style variable speed motor. If that is correct..... I'd recommend calling for warranty service. That motor is over $1000.
 
  #7  
Old 01-13-18, 10:58 AM
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i dont know whats going on, its working now.
 
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Old 01-13-18, 11:14 AM
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nvm...
when it kicked on it made a loud growl and was vibrating badly. when i hit "on" on the thermostat it makes a "bong" from the fan like its trying to go and eventually it does. could the bearings be shot?
 
  #10  
Old 01-13-18, 11:21 AM
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Process of elimination.

If it was the bearings it would do it all the time. Not only on Auto.

Did you try jumping the stat to see what happens.

Posted at the same so don't know if this is relevant.
 
  #11  
Old 01-13-18, 11:26 AM
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how do i jump the stat? take it off the wall and jump which wires?
 
  #12  
Old 01-13-18, 11:32 AM
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but would it be the thermostat? because right now it working fine, but it i go switch everything off then back to " heat" and "auto" nothing happens or it kicks on and off until it eventually starts working fine.
 
  #13  
Old 01-13-18, 11:43 AM
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That is why I mentioned your stat. It seems to be the component common to all your problems.

By jumping the stat it's like putting it in manual mode, which runs fine, but auto doesn't.

The fact that it works fine in manual to me means the blower is fine, your board is fine, and you have the same problem with the AC.

Unless I'm missing something the only common denominator to your problem is the stat.

As far as jumping the stat, it would only provide the same results as manual mode.

Your loud growl sounds like a blower problem, possibly a defective squirrel cage or motor but that is something that has to be checked from there.

Just my thoughts.
 
  #14  
Old 01-13-18, 11:44 AM
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When the stat is in COOL or FAN ON..... the blower is told to run on high speed.

When the stat is in HEAT/AUTO ..... the blower on medium speed is controlled from the timer section on the furnace control board.

FAN ON takes precedence over everything. It turns the fan on high even in HEAT mode.
 
  #15  
Old 01-13-18, 12:14 PM
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it doesn't matter if its AUTO or ON the result is the same. i opened up the stat and jumped red with white works fine, until i jump it with heat, after 30 seconds the fan dies. with heat off the fan works fine. i switched it on and off with the heat off, kicked on and stayed on every time. yeah the sound worries me, is there any way to test the motor itself?
 
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Old 01-13-18, 01:03 PM
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The red and white is the heat connection.
Red to green would be blower only.
 
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Old 01-13-18, 02:47 PM
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my bad, thats what i meant
 
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Old 01-13-18, 03:20 PM
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so i opened up my furnace and hit the last code button and it flashed 4 times indicating the limit switch, which probably activated when the fan cut off letting the furnace overheat with no air flow. it not the t-stat as far as i can tell, its there anything i should check the voltage on?
 
  #19  
Old 01-13-18, 08:35 PM
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just tested all the fan speeds, resistances are fine. i don't know what else to check. it sounds like it's tripping out, i'll jump the connections to turn the heater on and a little bit after the blower just dies and wont come back on even with heat off. its like it has to cool down or something before it will start again. still running fine with the fan in ON and heat OFF.
 
  #20  
Old 01-17-18, 05:47 PM
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blower works fine when it in ON or with COOL in AUTO. when i turn it to HEAT and AUTO the blower doesn't come on but the furnace starts and runs fine until the limit switch trips. if i turn it to HEAT and ON the blower will start with the furnace and shut down after .5-1 minute. no codes on the board except the limit switch that engages because the blower isn't working properly. i've tested the limit switches, capacitor, fan speed resistances, thermostat, filter, checked for lose or frayed wires and the pressure switch. the only other thing i can think of to do is change out the circuit board. everything magically started to work yesterday and now today got the same problem. any ideas?
 
  #21  
Old 01-17-18, 06:10 PM
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With the DIP switches on the control board..... is your furnace set to 1STG or 2STG ?
On just a call for FAN..... the blower runs at heating low speed.
Depending on the switch setting.... the blower changes speed depending on first or second stage operation.
 
  #22  
Old 01-17-18, 06:19 PM
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its set to STG 1 at the moment
 
  #23  
Old 01-17-18, 06:40 PM
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It was just running for the past hour fine, turned it off and back on and right back to not working.
 
  #24  
Old 01-17-18, 06:49 PM
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If it ran fine for an hour..... I'd have to think it's the control board. Motors don't usually run that long if they have a problem.

Blower motor wiring connections at main board.
black on HI cool terminal
blue on HIGH heat terminal
orange on LOW heat terminal
white on neutral terminal.

If you have a meter.... set it to read 120vac. Put one probe on white/neutral.
With the other probe.... check the HI and LOW heat terminals. One needs to be live during heating. If they are both dead..... the board is at fault.
 
  #25  
Old 01-17-18, 07:01 PM
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Iíll try that first thing in the morning, if that doesnít work Iíll just call a tech out. Thanks for the advice, I really appreciate it
 
  #26  
Old 01-17-18, 07:03 PM
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You're welcome. Good luck and let me know what you find.
 
  #27  
Old 01-18-18, 07:54 AM
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So for this to work I need to test the HIGH and LOW HEAT terminal when the fan is supposed to be on and not working correct?
 
  #28  
Old 01-18-18, 04:18 PM
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Yes.... that is correct...........
 
  #29  
Old 01-18-18, 04:33 PM
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its been working all day... but when it breaks again ill try lol
 
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