Posted: 5/8/2017 5:27:43 PM EDT
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Both the upstairs and downstairs HVAC units are not working. Both have the same problem. Indoor sections all work fine. Outdoor units both have power and both turn on when activated by the indoor thermostats. Outdoor unit Fans both turn on and turn. However, the coils inside never get cold and the coils outside never get hot. Both units were working relatively recently.
I'm assuming its a compressor issue and maybe a capacitor issue. I've replaced the silver capacitors in the pictures before and I thought they ran both the fan and compressors. However, it looks like both units have a second capacitor(the black phillips one) that I have never paid attention to before. What does this second capacitor do and is that something that would allow the fan to spin but not kick on the compressor? It looks like the second capacitor has a diode across the terminals. The second capacitor has one lead that goes to a relay and one that goes to the contact switch. I tested the silver capacitor and it appeared to check out. The black one is rated for 161-193mfd. When I pulled it out it and tested it, it started at 179 and then gradually dropped to 172. Not sure if that checks out or not. 
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The silver one is a dual run cap with the 7.5uf side going to the fan motor, and the 40uf for the compressor. The black one is a start cap for the compressor that feeds through the start relay which is the square thing just above it. If the caps check out, I'd look at the start relay or the circuit breaker (just below the cap), and look for burnt/corroded contacts on the contactor.
Have you measured the current being drawn by the compressor run winding? To test the start relay (potential relay) - How to test a potential relay part 1 How to test a potential relay part 2 How to test a potential relay part 3 |
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So I just put everything back on both units and tried them to test voltage. One of them started right up(both compressor and fan). Coils got warm although the heat of the air being blown out the top by the fan wasn't that warm so it wasn't operating 100%. After 5 minutes the compressor kicked off but the fan stayed on. I checked voltage though the relay. Relay has the black wire on one side and two different yellow wires on the other. Testing voltage between the black wire and one yellow wire was 240. Between the black wire and the other yellow wire was 300 volts.
The other one the fan started but the compressor did not. |
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You have a lot going on, the description of the dual cap and start kit is correct. Looking at this picture do you see the terminal that looks loose? If you push in the contacter manually does the fan and compressor start? If they do you may have issues with charge and pressure switches are taking compressors offline.
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Quoted:
You have a lot going on, the description of the dual cap and start kit is correct. Looking at this picture do you see the terminal that looks loose? If you push in the contacter manually does the fan and compressor start? If they do you may have issues with charge and pressure switches are taking compressors offline. https://www.AR15.Com/media/mediaFiles/259573/IMG-1594-204608.JPG |
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If caps are fine then most likely issue with refrigerant. You probably have a leak somewhere and the internal safety has the compressor locked out.
Probably time to replace the HVAC unit, but until then have them fix leak if it's not too expensive. Gives you more time to shop around. You probably have R-22, but they make R-427A which is compatible with R-22 systems since R-22 is being phased out and expensive. |
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Quoted:
So they both crapped out at the same time? I see you read 240 v and then 300 ........ How can you get 300? 
The yellow/black wire comes from the secondary cap(black cap), black wire comes from the contact switch, yellow goes to the dual cap(silver). Putting my multimeter between the black and yellow wires and black and yellow/black wires, one set has 244v and one has 305v. This is right after startup. On the unit that the compressor doesn't even come on, its 244 across both sets. By the way, what is this thing? Its circled in blue in this picture: 
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