Nothing works - cool, fan, or heat. Please help.


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Old 08-27-12, 03:46 PM
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Exclamation Nothing works - cool, fan, or heat. Please help.

I have a central air and electric furnace. The condenser unit was installed last summer. I had a new evaporator coil installed last month to match the outdoor unit. The previous owner didn't replace the coil with the condenser. I called the technician back out because I was only getting about an 8 degree drop. He came back out and I got 10. Later the same night everything shut down. The air conditioning, heater, nor fan will come on. I flipped the breakers in the main box, the one at the furnace, and pull and reseated the disconnect at the condenser unit. I have a snap on multimeter. I'd greatly appreciate any help in tracking down this problem. It took me 3 weeks to get the technician out here after the install and he isn't returning my calls for this problem either. It's 101 degrees in my house right now and it's unbearable.
 
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Old 08-27-12, 04:26 PM
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with power on to furnace you need to check ac voltage between R and C. Look for a low voltage automotive style fuse in the furnace or control board. It may be blown.
 
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Old 08-27-12, 07:11 PM
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There is a green wire (i'm guessing this is ground) that is screwed onto the blower motor housing but the other end is loose. I assume this should be screwed onto the enclosure around the wheel? If so, any particular place?

I purchased and installed a new transformer. From what I read it seemed like a decent place to start. I was told to get this transformer 25.2V CT 2.0A Heavy-Duty Chassis-Mount Transformer with Lead - RadioShack.com from radio shack. The original transformer had 5 wires and was rated at 60va. I don't have a heat pump. Was this an ok replacement or do I need to get an hvac specific transformer? Regardless, it did not fix the issue.

My air handler is probably 15 years old. There is no control board other than where the thermostat wires screw on to. I can't locate a fuse. I removed all the screw on panels inside the air handler. Seeing as there is no fuse in place I thought this may have caused the transformer to blow if there was a surge of some sort. When I purchased the new transformer I got an inline fuse holder and a 1 amp fuse to install.

I will check the voltage between c and r and report back.
 
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Old 08-27-12, 07:19 PM
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I would get a 60VA transformer and install a 3A fuse in your inline fuse holder. The holder should be installed on the secondary side of the transformer. To properly diagnose your system you need to use a voltmeter.
 
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Old 08-27-12, 07:36 PM
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The fuse holder I got takes glass fuses, will this work? I believe it says it can accommodate up to a 10A fuse. It needs to be installed on the 24v side right? I want to make sure I'm not confusing the primary and secondary. I just screwed the green wire onto the housing around the blower wheel, is that what you're supposed to do to ground the motor? The blower has a 370VAC run capacitor. It doesn't appear to be leaking or bulging anywhere. Not implying that it would be the problem, just making note as I have it the blower assembly out at the moment. I'm about to put it back in and I'll take the voltage readings. My meter is made by snapon and can handle ac and dc (purchased for automotive) with several settings.

When you mentioned testing across c & r, can I test by the screws or should I disconnect the wires and test them directly?
 
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Old 08-27-12, 07:39 PM
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yes, the glass fuse holder will work. Green wire put to housing is fine. Yes, fuse goes on 24V side. test at screws with wires in place.
 
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Old 08-27-12, 08:12 PM
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Testing across these 2 terminals I have no voltage.
 
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Old 08-27-12, 08:18 PM
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I will go to grainger tomorrow and get a 60va transformer. If possible, I'd like to troubleshoot with the less expensive radio shack one before installing the $60. I'd hate to blow the transformer by accident. Hopefully at this point the transformer that's in there hasn't caused an additional ghost to chase.
 
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Old 08-27-12, 08:24 PM
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you need to verify voltage into the transformer. If you use that in-line fuse only your new fuse should blow and not the transformer.
 
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Old 08-27-12, 08:31 PM
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This is the transformer grainger told me to get when I called them earlier. Their local branch was closed at that time so I haven't had a chance to pick it up. WHITE-RODGERS Transformer, 24v Output - Transformers - 6WU94|90-T60C3 - Grainger Industrial Supply Does that look right? it has an extra wire. I assume you cap it off.

Where do I test to verify voltage coming into the transformer?
 
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Old 08-27-12, 08:36 PM
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yes, that will work fine. You should have 2 extra wires. It is a multi-volt transformer, it will accept a primary voltage of 120, 208, or 240V. It just depends on your application.

You check voltage to the transformer where the wires connect (dangerous if you dont know what you are doing)
 
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Old 08-27-12, 08:48 PM
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I wasn't being clear. I meant it had 1 more wire than the original. I took some pictures that shows my setup. The silver transformer where the thermostat connections are is the one I replaced. I'm sure this is a stupid question, but is the square box that has wires going to it a transformer as well? The reason I ask is because it says line and load on the top where the wires are.

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Old 08-27-12, 08:55 PM
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I really appreciate all the help you're giving me.

To test the voltage to the transformer would I be able to remove the wire nut connecting the wire from the harness to the transformer - then use an alligator clip on the live wire? If so, where would I put the second lead?
 
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Old 08-27-12, 09:05 PM
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I tried testing it as I would for automotive - I removed the wirenut placed 1 lead on the wire coming into the transformer and clipped the other onto the metal casing. I got 114 volts.
 
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Old 08-27-12, 10:08 PM
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I can see a transformer in the first and last photos.If power in and no power out it's no good.
 
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Old 08-27-12, 11:47 PM
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I thought it was. I guess ac and heat have separate transformers in my unit.
 
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Old 08-28-12, 07:24 PM
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Can anyone tell me how to further troubleshoot my problem? How many volts should be coming from each wire of the 24 volt side of the transformer?
 
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Old 08-28-12, 07:46 PM
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you measure ac voltage across the 2 secondary leads to test voltage. Unlike DC and automotive circuits you do NOT test each leg to ground.
 
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Old 08-28-12, 07:48 PM
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Glad you cleared that up. Was the way I checked voltage to the transformer correct?
 
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Old 08-28-12, 07:50 PM
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no, you would check between both wires. (one lead to one wire... the other lead to the other wire)
 
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Old 08-28-12, 08:00 PM
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Across the red and black wires TO the transformer I have 65 volts.

I have a relay between the wire harness and the transformer so it's a little confusing to me. I traced the wire from the wires from the transformer back to the wires they are connected to. Then tested at that connection.
 
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Old 08-28-12, 08:03 PM
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not enough.... check your connections......
 
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Old 08-28-12, 09:57 PM
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Fixed. Thanks so much hvactechfw. There was a broken wire that looked like it had been pinched or something.

I still have to try to get the technician who installed my coil back out here. My initial complaint was my ac wasn't cooling enough. I'd be lucky if I could maintain outside temperature and at max I had a 10 degree drop from the vent to the return. He said that it was a mismatched system and recommended a new coil. He installed a matching coil for the condenser unit. He said it would take a day or so to get the real temperature drop, it never went above 8.

He left the nut loose that connects the line to the coil and it leaked out some of the refrigerant. When he finally came out 3 weeks after install he said that he tightened the nut and added refrigerant. He had also put the wrong piston size. He told me that should fix the problem but if not the fan blower speed may need to be adjusted. I've gotten a maximum of 10 degree drop. Any suggestions as to what I could try or bring up to him?
 
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Old 09-03-12, 07:28 PM
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Any suggestions for not enough cooling?
 
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Old 09-04-12, 12:08 AM
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have the unit serviced...................................
 
 

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