Lennox AC won't start

kcd1803

I have a Lennox AC unit HS23-311-2p , the other day it just stopped working I've checked the connectors from the thermostat to the furnace to the unit and all are okay. I have continuity in both fuses in the outside box as well as the indoor fuse box. I then found a burned wire on the red wire connected to the start capacitor, I have replaced the wire and have power running through it. I haven't checked the connector at the fan motor or the compressor but I don't hear anything. Before tearing the whole thing apart and checking the connection at the fan and compressor is there anything else I should try first? Thanks for all of your help!

scottmcd9999

Does the contactor activate when the stat calls for cooling?

Do you have 240v at the contactor? If not, check for tripped breakers.

Are you sure you're referring to a start capacitor? Is it silver/grey, or is it black? If it's silver, that a run cap, and quite often a faulty run cap can cause the system to stop. You can check caps if you have a meter capable of doing this, or you can just drop by the local HVAC supply house and get a replacement. You'll need to know the microfarad rating (like 40 +5, if it's a dual cap) and the voltage (either 370 or 440)

kcd1803

Looks like what the user guide calls a start capacitor is now called a run capacitor, what part # is compatible with my unit, when I type in the # on the actual unit it shows a unit that looks like it has the same connections, but is oval not round...does that matter? Thanks again for your help!

scottmcd9999

No - there are Start capacitors, and there are Run capacitors. They're two different things.

Doesn't matter about oval or round, either will work. You're concerned with the microfarad rating and the voltage.

I have no idea what is compatible with your unit. Contact your local HVAC dealer to find this out.

MikeKy55

The start/run capacitor on my Bryant died suddenly Monday. Condensing unit did nothing. My job workload deemed I call a pro. I happen to know one I trust. He came out later that day and tested it. He replaced the capacitor and all was good. It was about 115.00 and in my not so humble opinion, well worth it. It was 98º that day and I couldn't just wait and test it myself.

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Doc Holliday

The mfd/uf needs to match. The voltage can go up from 370 to 440 or it can stay the same.

If there are no numbers on your old cap, if they're faded, post the make, model and serial number of your condenser.

Generally a start capacitor runs 70uf and higher.

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Thanks.