AC compressor

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My 1986 Lennox AC compressor unit just stopped running, the fan isnt running and no noise comes from the unit, I reset the breakers and the thermostat is the old round analog Honywell, its calling for cooling. Ive never worked on this but is there anything I can test with a V meter before I call a pro. 3 weeks ago I lost all freon from a big leak and had it fixed, all has been fine until today. I would think at least the fan would run.
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When this happened to my 1991 Lennox, it was the timing board. That particular board delayed turning the thing on for 5 minutes once it was told to by the thermostat. This was to make sure the old mercury therms had time to settle and prevented on-off-on-off. The tech said it was pretty obvious that the board burned out. One possibility?
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That sounds logical
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On 8/22/2010 9:06 PM, ransley wrote:

If there was a thunderstorm, a voltage spike could have blown the run capacitor. If your air handler fan doesn't run, it's a power problem there because the 24 volt control voltage comes from the furnace/air handler. Without the 24 volts AC, the condensing unit where the compressor is will not come on. If you can push in the insulated contact carrier on the condenser contactor and the fan and compressor run, you'll know it's not getting control voltage from the furnace/air handler.
TDD
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On Aug 22, 10:01 pm, The Daring Dufas <the-daring-

What does the condensor contactor look like where do I find it, I wonder if the tech left a wire loose since it seems like it just has no power. I do know I dont think it was installed with proper gauge wiring , Its about a 60 ft run of 2 pieces of 10 ga and it rattles in the pipe and at the breaker on turn on. All these years of rattling could have loosened something.
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ransley wrote:

It's the only (usually) relay-looking-gizmo in the outside unit. It supplies power to both the fan (120) and the compressor (240). If both are not working, the obvious culprit is the only thing they have in common - the relay.
That said, it could be the relay itself is broken (fried, etc.) or the voltage that activates the relay (24V) is missing.
If the relay, they're not TOO expensive and, if your hand fits a screwdriver, you should be able to replace it. Label the wires - taking several pictures is better - and take the old one to Graingers. Say "gimme one like this".
Remember to wear eye and ear protection when working around electricity and, um, er... one other saftey precaution, but I forget...
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Yeah, we can't tell him the other safety precaution. It's too complicated.
I think he will find that the condensor fan is also 220 VAC. And has a run cap.
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Stormin Mormon wrote:

Ah, right. I forgot.
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Happens to the best of us. We all forget something or
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When I push in the relay it runs, so now I will go back out and see if its getting 24v.
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ransley wrote:

Yep. It's either not getting the 24v OR unable to use the voltage cause the relay itself has given up the ghost, taken a dirt nap, singing in the heavenly choir, or passed this way only once to brighten our lives, provide endearing memories, and let us chill.
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On 8/23/2010 1:32 PM, ransley wrote:

The low voltage wires going to the contactor coil are usually yellow in color, sometimes one is blue which is the common.
TDD
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wrote:

I know... keep one hand in your pocket!
What do I win?
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wrote:

Umm, messy underwear?
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I've never heard of a wire or a breaker "rattling". The freon lines on some units can be noisy and that might be what you hear.
You can check for 240vac at the unit. It should be easy to trace to the contactor (a big relay). The contactor is a 24vac activated relay that supplies 240vac to the entire unit. The inside half sends the 24vac. It is possible to manually activate a contactor by pushing it down carefully with something. The compressor and it's fan are both activated by the contactor. If there are any additional controls such as the startup delay board they will most likely be on the 24vac side. Both the compressor and the fan will use run capacitors but they may be combined in a single can. Ther may also be a start capacitor on the compressor. Since nothing is running I doubt it's a capacitor.
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I can hear the wires "Rattle" inside the conduit and the breaker on the main panel makes a zip noise when it powers on, I bet it should have been a larger gauge but they had no more room in the conduit. I mentioned it to them on install and they said 'its ok", but I know it would have been rejected by an inspector. I didnt get a permit or an inspection for the install, In 96 I didnt think permits-inspectors were a help. Thats why I wonder is I have any power since nothing works, but im no electrician.
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Wires will never move due to being energized in this application. They will get hot if they are too small but they won't "rattle". You are hearing something else.
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On 8/23/2010 7:50 AM, jamesgangnc wrote:

It's not unusual for wires to move or rattle inside a conduit even if the wire is properly sized for the load. The starting current of an AC compressor can easily be several time the run current of the whole unit. Wires can and will dance under the right set of circumstances.
TDD
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wrote:

You're an idiot. Wires do not move in this example.
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On 8/24/2010 7:18 AM, jamesgangnc wrote:

I only have four decades experience in the field and I see it all the time. In an industrial environment I've come across it a lot where there are a numerous high current starting loads for motors. The wire can actually change length under heavy load. I've seen insulation rubbed of a wire because of this movement. The OP can hear the #10 wires jump inside the conduit when his AC unit stars. When you get your PhD in know-it-allogy, come back and call me names.
TDD
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