outdoor unit's fan doesn't rotate


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Old 09-08-04, 10:50 PM
lasanto
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Question outdoor unit's fan doesn't rotate

i have a residential airconditioning unit with split system from "day&night". the unit is already 20 years old, but has seldom been used until recent couple years. several questions associated with situations as follows:
1) when control panel was turned on, the compressor of the outdoor unit was immediately on. i could feel one copper tube was cold, but, the fan of the unit did'nt rotate at all (this may have been this way for some time without my knowing). i checked the register inside the house and could feel some cool air came out of it. but, after approx. 15 mins, i found that the compressor was completely shutoff. did this auto shutoff is from the non-rotating fan?
2) i had an electrician came to take a look. he took off the door panel, and used meeter doing some testing. i saw and heard that the meeter did have responses from several individual touches on the connecting points on one metal panel on the top of the unit's door frame, but, there was one or two contacting points had no response. the electrician did try to rotate the blade by hand, but, the fan still didn't get turn on. after approx. 5 min, the compressor was shut off automatically. the electrician told me that the fan which has motor as an integral part needs to be changed. i was a little puzzled and asked that if one connecting point didn't response the meeter, how could he determine that fan/motor has problem? i thought the fan might not get electric current flowing in. but, he said, he used hand to give fan a torque to rotate it for several times, but fan still didn't get turn on. he said, he could try with his own capacitor, so, he went to his car to look for it, but, then he said he coulndn't find it. he was quite sure that fan/motor had been broken down which needs a new one and also, a new connecting board (capacitor?). does this sound a good diagonsis?
3) i called "us airconditioning" to see if they have this type fan/motor parts, they told me that they might have it, but they couldn't sell it to an individual except to the contractors. does this sound familiar?
4) is there any good website to search for this type parts?
thank you very much for your time and help!

lasanto
 
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Old 09-09-04, 05:23 AM
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You could have a bad fan motor, but I'd check the capacitor first. They go bad and when they do the fan motor won't run. When the fan doesn't run the compressor will start and you get some cool for a short time but soon the pressures rise inside the coils because the fan isn't moving any air and the compressor trips of due to high head pressure. This is perfectly normal and most likely your unit would work fine when you get the fan working again. I'd bet the chances are better than 50-50 that you have a bad capacitor. I'm surprised the electrician didn't pick up on that.
 
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Old 09-09-04, 07:34 AM
lasanto
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re: the outdoor unit's fan doesn't rotate

thanks very much for the helpful thoughts. i did question the electrician why not make sure that capacitor is bad first, then decide the fan/motor is bad. he said, he turned the rotary fan by hand to give it a torque, but, fan is still not turned on, so he is 99% sure that fan/motor is bad. he gave an example that by hand turning the fan inside car's engine, you can start the engine, even the starter is bad. so, now, the fan/motor can't be turned on when the compressor is on, so, the fan is bad. i'm confused by his logic and explanation.
he said that he could install the fan for me with couple hours labor fee, but, i should also buy the capacitor. does this sound reasonable?
thanks.
 
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Old 09-09-04, 10:32 PM
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I would say that he has all his bases covered. When a capacitor goes bad the motor will sometimes run, but run slowly. Often the motor will be real hot as well. I would say that if the motor doesn't run, but is hot you may just have a bad capacitor. You could replace the capacitor only have the motor die as well a short time later because running the motor coil very hot doesn't do it any good and will greatly shorten its life.

Giving the fan a spin to see if it will run would be something I would try. My objective would be to see if the motor is mechanically binding somewhere. When I see that happening I get a new motor. I don't know what was found in your particular situation but it sounds like the guy didn't remove and check the capacitor. If it's completely open I wouldn't expect the motor to start very well on its own.

I would start with a new capacitor and go from there. I don't know how hard your fan is to get at, but I could easily replace mine and the capacitor in an hour and have time left over for a cup or two of coffee. Maybe your guy has a ways to drive and he has to charge more for his travel time.
 
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Old 09-11-04, 05:55 AM
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Alot of HVAC shops will only sell to dealers but that does not mean there's not a place that will sell it to you. Look in the Yellow pages under electric motor shops or look for a Johnstone Supply. Also alot of the supply houses will let you set up a "cash" account and then you can buy it.

Why did you call an electrician anyway?
 
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Old 09-15-04, 07:43 AM
lasanto
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re:outdoor unit fan doesn't rotate

1) Thank you very much for the information on a/c parts store name and cash account method!
2) The electrician told me that he can fix electric related problems include the a/c unit, but, he won't do a/c maintenance such as addig refrigerant. the outdoor unit's fan could be rotated freely with hand, but, won't get turn on electrically. after checking out the electric wires connections which are all located on a metal panel (most connections have response to his meeter, except one didn't have response; the compressor can be turned on normally, but auto shutoff a little later). he suggested to buy a new fan and that metal panel which has all connection points, and he can replace both for 2 labor hours.
3) I asked if that panel is called "capacitor", he said yes. but, I don't quite believe that panel is "capacitor".
4) Just wonder if one or two contact points on that metal panel didn't respond to the voltage meeter measurement (all others do response the measurement, and the compressor can be stared normally), how to pin down the problem : fan is bad? or connector point on the panel is bad? or both are bad?

thanks.
lasanto
 
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Old 09-15-04, 11:39 AM
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On a normal residential unit the fan has 2 hots and a capacitor. The capacitor looks like a little tin can. If it was just a bad cap the fan would at least be wanting to start and if you gave it a little push it would normally start up for you.

What do you have coming from your fan and where do they connect.
 
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Old 09-15-04, 01:56 PM
bigjohn
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At the risk of alienating electricians, my experience has been that they are not good witn controls and motors. It's a lack of training thing, not that they are dumb. Here is how a competent HVAC tech would check your motor:

First, see if the motor is hot or cold. Hot tells you that you're getting some kind of power to the motor. Cold usually means no power is getting to the motor, or the internal protector is open and won't reset, or the motor is completely burned out[open windings].

Hot motor:

Check the voltage to see if it's right, check the motor for bearing wear or excessive end play, check the capacitor [is it open?, is it shorted? What is it's mfd capability vs. it's rating?]. Let the motor cool down, ohm out the windings. If the motor will start check the amp draw against the nameplate rating.

Cold motor:

Check the voltage, ohm out the windings, look for a burned/loose terminal at the wire ends.

By now the problem will have revealed itself. Roughly 6 months ago I had a call where the condesner fan motor was not running. The motor was cold. I had a open circuit to the motor windings. I noticed that the wires had been strapped to a support bracket and the cable tie holding them has deteriorated. One of the wires had chafed and, although it hadn't fully rubbed thru the insulation, it had chafed enough to break the wires strands inside the insulation. I cut the wire and stripped back to good, crimped on a butt connector and taped the connector. Then I secured the wires onto the bracket with some new cable ties. I used maybe 5 cents worth of materials which is a lot cheaper than a motor changeout. Something like this is the exception, usually either the motor or the capacitor is bad, but it pays to check everything. Recently, I had a Kenmore clothes dryer with a similar situation. The dryer was dead. First thing I checked was the power, then the door switch. I noticed that the clip holding the door switch wires up on the cabinet and away from the drum was gone and the wires were laying on the drum where one of them had rubbed thru. A couple butt connectors, some electrical tape, and a couple cable ties later, we were back in operation.
 
 

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