a/c fan/blower motor

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  #1  
Old 03-16-04, 08:21 AM
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Question a/c fan/blower motor

I live in Ft. Worth, TX and I'm having problems with my centarl a/c. The blower/fan is acting very strange. I have a split system that is kinda old. The outside unit is an O'Keffe-Merrit unit 4 ton, the inside furnace is a whirlpool. When the heat is on, the fan/blower works perfectly. When the unti is switched to heat, the blower will run for approximatley 2 minutes then stop. It makes sounds like it is trying to re-start but is unable to do so. Have cleaned and oiled the blower/fan, replaced the capacitor last summer. The filter has been changed regularly. What could be causing this? The thermostat? wrong capacitor? Again, when the heat is on, there is no problem.

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  #2  
Old 03-16-04, 08:53 AM
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When the heat is on, the fan/blower works perfectly. When the unti is switched to heat, the blower will run for approximatley 2 minutes then stop. It makes sounds like it is trying to re-start but is unable to do so. Have cleaned and oiled the blower/fan,
If you go to fan on will the fan run???? You say heat and then heat again??? is it a 2 speed motor ??INFO INFO

ED
 
  #3  
Old 03-16-04, 08:56 AM
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blower/fan

Sorry for the confusion...when the heat is on, the blower/fan works fine...when switched to a/c the problem starts. It is a single speed fan. Thanks again
 
  #4  
Old 03-16-04, 09:00 AM
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Will the fan turn on when you put the tstat to just fan on???? ED
 
  #5  
Old 03-16-04, 09:03 AM
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blower/fan

if the unit is set to heat, the fan will turn on in the on position, if it is set to cool, it will run for just a couple of minutes. This happens if the fan is on "on" or "auto". It seems the only problem is when the unit is on "cool". Thanks for the responses!
 
  #6  
Old 03-16-04, 09:16 AM
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At the tstat on cool push it up not calling Jump R to G does the fan come on and stay on?
 
  #7  
Old 03-16-04, 11:40 AM
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b;ower/fan

Not sure what your asking...maybe to clarify...put the unit on "off", then will turn the fan to "on" and it will run for a couple of minutes then stop. When the heat is on....the fan/blower works fine. Hope this clarifies..thanks again for all the responses
 
  #8  
Old 03-16-04, 01:18 PM
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sounds like possibly the blower relay is dropping out when engaged for cooling. is this a gas unit?
 
  #9  
Old 03-16-04, 01:37 PM
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Not sure what your asking...maybe to clarify...put the unit on "off", then will turn the fan to "on" and it will run for a couple
With hvac4u here on the relay but we dont know for sure.

Turn the tstat off open it up jump from R to G right there .

does the blower stay on or not????????????????? ED
 
  #10  
Old 03-16-04, 01:59 PM
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Check your blower. Are you sure it's not a multi-speed? Sounds like high speed is going out. Is it belt drive or direct?
 
  #11  
Old 03-16-04, 02:11 PM
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blower/fan

This is a gas unit, direct drive. I'm assuming it's a single speed. will check and get back to you....what I'm understanding so far from the repsonses is that the problem is probably with the thermostat or a relay, rather than the blower motor?
 
  #12  
Old 03-16-04, 02:34 PM
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blower/fan

I jumped the red to the green as suggested and the blower came on. I really appreciate the prompt replies, thank you again
 
  #13  
Old 03-16-04, 03:56 PM
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I jumped the red to the green as suggested and the blower came on.
Ok now was it a lose wire or screw in the tstat or is it in the tstat.

check it out ED
 
  #14  
Old 03-16-04, 04:03 PM
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blower/fan

The screw was tight and the wire was tight, so am I to assume it is the thermostat?
 
  #15  
Old 03-16-04, 04:42 PM
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You can play with it till your sure Id say. Its like this if you can jump R to G and the blower comes on and run as long as you hold it there then its the tstat. You see the tstat turns the blower on and off by R to G that goes to a relay in the furnace we want to make sure its not that.

Think for blower ON at the tstat its just a switch turns on R to G

When you call for cool the tstat turns the AC on by R to G and Y for fan and cool . ED
 
  #16  
Old 03-16-04, 04:59 PM
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blower/fan

Thanks for all the help. You guys are awesome. I know just enough about a/c to be dangerous!!! So again thanks for the help
 
  #17  
Old 03-19-04, 05:10 PM
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blower/fan

Ok, getting frustrated, replaced the tstat and it does the sae thing. When set to cool, the fan will run for a few minutes and then stop. Any ideas?
 
  #18  
Old 03-20-04, 04:56 AM
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Lets start at the begining. You said when it stops it sounds like it's trying to start but it wont. With the blower door off the unit and safety door switch temporarily jumped. Run it in cool. When the fan stops use a pencil and see if you can turn the blower wheel freely.
 
  #19  
Old 03-20-04, 06:54 AM
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Thanks for the response....tried what you suggested...the blower wll turn freely
 
  #20  
Old 03-20-04, 06:55 AM
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With Matt here lets start over. You said that the blower ran on R -G now you say it stopped.?????????????? New tstat same thing. If the motor will run for a while then stop of its own. Its lost the AC speed on it or the internal thermal overload ED
 
  #21  
Old 03-20-04, 06:59 AM
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With the new tstat installed, it's doing the same thing...i can jump the R-G and it will run....just like with the old tstat installed
 
  #22  
Old 03-20-04, 07:03 AM
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With R &G together you say the blower will keep on running for as long as they are together ?????????????????? ED
 
  #23  
Old 03-20-04, 07:07 AM
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I havent held them together that long....maybe 30 sec to a minute...but yes.....as long as I hold them together it will run
 
  #24  
Old 03-20-04, 07:44 AM
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ok 5 min or will it run for 10 min with R &G together and it just keeps on running, dont stop at all ????????????????Did you get the same tstat ?????ED
 
  #25  
Old 03-20-04, 09:07 AM
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not the same type of tstat....should I actually connect the R-G wires to see if it will run for an extended period of time? haven't done that...just held the wires together
 
  #26  
Old 03-20-04, 09:13 AM
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Yes put R and G together let it run this will tell us if its the motor or down on that end ED
 
  #27  
Old 03-20-04, 09:20 AM
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ok....put red and green together and it won't run now at all, previously it would
 
  #28  
Old 03-20-04, 09:29 AM
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Does the motor smell or feel hot????? You also have to look and see if the blower relay did pull in or not. The motor still runs ok on just heat???????????????? Look at the wire schematic there you sure its not a 2 speed motor This also should tell you where the blower relay is ED
 
  #29  
Old 03-20-04, 09:48 AM
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blower/fan

The motor doesn't feel hot.....looked at the scematics and it does say it's a multi-speed motor....I get a humming sound now when the unit is turned on....wont work on heat either now, thanks again for all the quick responses!!!!
 
  #30  
Old 03-20-04, 09:49 AM
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blower/fan

also have discovered that if I let the unit rest for a 30 minutes or so...then it will come on....could it be that something is overheating and causing it to stop? and then when it cools down it will run?
 
  #31  
Old 03-20-04, 09:57 AM
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also have discovered that if I let the unit rest for a 30 minutes or so...then it will come on....could it be that something is overheating and causing it to stop? and then when it cools down it will run?
If the motor will run for a while then stop of its own. Its turning off and on with the internal thermal overload that a lot of motors have when it cools down it will come back on Is what Id say Think you need a new motor not a tstat


Unit should have blower like on a lower speed for heat and most of the time the blower is on the high speed for AC

ED
 
  #32  
Old 03-20-04, 10:04 AM
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blower/fan

Thanks....I replaced the blower about 5-6 years ago, is this a normal lifespan for them?
 
  #33  
Old 03-20-04, 10:59 AM
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Cant say on the motor. Lots has to do with it. Does it have to work hard all the time . Is it to small for that 4 ton AC. Do you keep the filter clean all the time . You sure you put the same capacitor on it when that went out on you. You didnt over oil it. Use 3 in one oil or WD 40 when you should have used just a #10 oil on it. Lots and Lots of ifs ED
 
  #34  
Old 03-27-04, 01:08 PM
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blower/fan motor

OK.....I have replaced the blower motor, new capacitor and tstat. It does the same thing. Thought I had it fixed with the new motor, it ran for about 15 minutes then stopped. Tried jumping from red to green in the tsat, nothing. You can hear a hum from the motor. The motor does not get hot however. Thanks for any ideas!!!
 
  #35  
Old 03-27-04, 01:45 PM
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This is a gas unit, direct drive. I'm assuming it's a single speed. will check and get back to you....
never did???

Just what motor do you have .How many speeds. Is it wired right?
Out of the blower relay do you read 110 volts at fan on??with the breakers off to the outdoor AC condenser.Will the fan run at fan on or R to G? Is there a wire schematic there on the door of the furnace. Is that how its wired ??? ED
 
  #36  
Old 03-27-04, 03:05 PM
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blower/fan motor

I think I have discovered the problem, I believe it is the relay. I traced the wires from the blower motor junction box up to the what I beleive is the relay and assembly. One wire appeared burnt and the relay was hot and humming when the power was turned on. I am assuming that this is the relay, it is where the wiring from the tstat to the unit goes.
 
  #37  
Old 08-28-06, 05:54 PM
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fan motor work for a ehile then stop

I have a problem with my system. When I turn on the thermostat for the cooling system the copresor goes on but the blower wont work. after cut the power in the circuit breaker turn the cooling system on and the blower will work for few minutes then will turn off by if self. I changed the capacitor and still doing that.

Cn you help me??

Miki
 
  #38  
Old 08-28-06, 06:05 PM
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Also when I switch the fan mode from auto to on wont work unless reset the circuit breaker then will run for a few minutes and stop.
 

Last edited by DIYaddict; 08-28-06 at 07:26 PM. Reason: removed self quote-see above post
  #39  
Old 08-28-06, 07:00 PM
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Wink

mikito
sounds like its the blower motor there. get new one just like it mark whereand how all wires go.
Dont run outside unit if inside blower dont work.
ED
 
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