Condensor blows the fuse


  #1  
Old 08-03-02, 10:13 AM
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Condensor blows the fuse

Hello,
My carrier 13 year old 2 ton condensing unit blows the fuse when I turn it on. The first time I tried, I did see the fan going out side but then it stopped. I heard a buzzing noise, intermitantly for that brief moment.
The fan does turn freely. I think I will check the contactor. If I push it in, is this not a good idea since it blows the fuse? First I'll see it with the power off now. We did have a storm last night.
Of course this is after just fixing the upper unit with a new condensor .
Thanks,
Geoff
 
  #2  
Old 08-03-02, 12:51 PM
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When I twisted the red, green and yellow thermostat wires together and turned unit on, I saw a spark at the contactor outside and it blew the a/c cuircut breaker again. Does this sound like the contactor. All the wires seem tight in the contactor. I didn't inspect the capacitor yet.
Thanks in advance. Also it seems no a/c stores are open.
Geoff
 
  #3  
Old 08-03-02, 02:55 PM
bigjohn
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Look at the capacitor to see if it's bulged out, blown or leaking oil. Turn off the power and look around the compressor for the terminal box. Remove the cover. See any burnt wires? Make a sketch of which wire goes to which terminal, remove the wires and tape up the ends. Now turn on the power. If it still blows the fuses/circuit breaker then the problem needs further testing. If it stops blowing them then the problem is the compressor motor. to verify, scratch a clean place on the larger tube going to the compressor and use for an ohmeter to test for continuity between each terminal and the clean spot on the tubing. If the compressor is ok, you should NOT get a reading. A reading indicates that the comporessor motor is grounded. I remember a recent post about your a/c unit. I didn't know you had two units.
 
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Old 08-03-02, 07:29 PM
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Thanks for the reply. Yes I have 2 units, 1 upstairs and one for downstairs. The connection to the compressor was broken through the compressor. I replaced it with an Armstrong. Now this unit is acting up. Last year with the forums help, I changed a capacitor which fixed it.
I like your idea of removing the wires to see if it blows the fuse. I was just going to change the contactor and capacitor since maybe the run part of the capacitor for the fan is bad. I know it wasn't bulging 2 weeks ago. The fan actually started a few times but didn't keep going. It buzzed a few times. Then the fuse blows. I actually pulled out and tried this capacitor in the other old unit to help diagnose the problem. It wasn't bulging 2 weeks ago. I am hesitant to pull off the connection from the compressor since this was what was broken last time. I feel to play with that connection may be fragile. I may follow the wires from the contactor to the compressor and try removing it at the contactor side. I saw your post at clayb and will follow your advice. Maybe sears has the parts tomorrow so I don't have to wait till Monday if this is the problem.
The capacitor isn't bulging. The wire to capacitor looks a bit burnt (herm contact), though. The part of contactor that goes in and out also looks a bit black. I plan on changing these tomorrow, Monday, first thing. If I turn the unit on with the capacitor wires taped, would that tell me if the contactor is bad if the circuit blows? I am hesitant (scared) to pull off wires from compressor since this is what broke last time.

Thanks,
Geoff
 

Last edited by willkeeptrying; 08-04-02 at 11:53 AM.
  #5  
Old 08-04-02, 12:00 PM
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To recap-
I edited this above:
Possible burnt wire to capacitor. Otherwise, cap looks fine.
Slightly burned mark on contactor where it goes in and out. Probably from spark I saw.
Will replace contactor and capacitor and wire end to cap tomorrow.
Thanks,
Geoff
 
  #6  
Old 08-05-02, 08:24 AM
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Hello,
The saga continues- Replaced cap and contactor, fan starts to turn slowly but then pop- and the circuit breaker goes. I am wondering if it is the fan. It does turn freely. I'll try the disconnect the compressor wires and see what happens now.
Geoff
 
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Old 08-05-02, 07:37 PM
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Hi Big John,
I found some bad looking wire connections. One going to the capacitor definately needed replacement. One going to the compressor is also questionable. I cut off the end and replaced it. I took off the capacitor wires and taped them, all three, and still the same prob. Will check Ohms tomorrow and need to make sure the pin connections to compressor weren't soldered. My alarm guy is going to help with the wires. They should just slip straight off, correct? Should I spray it with anything to make them slip easier.
Thanks for your help.
Geoff
 
  #8  
Old 08-06-02, 03:29 AM
bigjohn
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The terminals slip right off the pins although they may be a little tight. They're not soldered on and you don't want to attempt to solder them on. Don't spray them because you don't want the spray to make an electrical circuit from pin to pin. If you're hesitant about removing the wires from the compressor terminals, then go the other way. Follow each wire from the compressor to it's termination. Remove them one at a time, [make a sketch of where they go] and isolate them. Now turn the power on and see what happens.
 
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Old 08-10-02, 08:21 AM
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Hi Big John,
Thanks again for the reply. My alarm guy spent 1 minute to hear my problem and said a short is tripping it. He barely looked.
I finally got a chance to pull the wires (been away on business) and see. First of all, I changed a wire connection to compressor since it was burnt looking. I put ac on and the fan ran but not at the normal speed, and no compressor. I pulled all wires at compressor and turned ac on and the fan went fast, at the normal speed. Interestingly, the circuit did not blow either time. I am about to do the ohm test. On my meter there is 2 settings one for 3 and one for 30. It is a radio shack multi tester. I'll report back.
Thanks,
Geoff
 
  #10  
Old 08-10-02, 09:48 AM
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When I touch the larger freon line and touch the compressor connection that goes to the "herm" part of the capacitor, I get a reading. I take this means over $1,200 out of pocket for a condenser? If so, the question becomes, I need to upgrade for an extension we will do next year. To upgrade the outside from 2 to 2.5 or 3 ton would mean an upgrade to the air handler and ducts. Could I do the compressor now and wait for the air handler and larger ducts and risk temporary icing 0f the coil?
Geoff
 
  #11  
Old 08-10-02, 10:29 AM
bigjohn
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It sounds like you have the compressor terminals isolated?? You want to use the largest ohms scale on the meter for testing to ground. Usually the scales are like Rx1, Rx10, Rx100, Rx1000, Rx10,000- like that. Test each terminal to ground using Rx10,000, a reading means the compressor motor is grounded. Then put the meter on an Rx1 scale and test terminal to terminal. No reading from any one terminal to another means a motor winding is open. I'm a liitle surprised that the breaker didn't trip when you still had the compressor wired up. Frankly, I wouldn't put in a larger unit now. Most compressor motor failures can be traced to a lubrication failure in the running gear of the compressor. It usually has to do with a system malady that allows the system operate in a manner where the refrigerant is not managed properly. One example is, with a dirty cooling coil, the refrigerant in the cooling coil doesn't completely vaporize and some refrigerant flows back to the compressor as a liquid and dilutes the lubricating oil which wipes out the running gear which in turn frys the motor. Ditto with an iced up cooling coil. So- if you put a larger unit on what now becomes an undersized indoor unit [relative to the size of the outdoor unit] with a dirty coil and inadequate return air ducting, it'll be goodbye new compressor. [7 to 8 out of every 10 residential systems that I've ever seen have poor ducting/return air grills] I imagine I'll get flamed for making that statement. Before you condem the compressor for sure, check your readings 3 times and make sure the compressor terminals are completely isolated. Borrow or buy a better meter if need be.
 
 

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