Run Capacitor, AC, outside blower, and a couple technical questions


Old 07-09-13, 10:34 PM
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Join Date: Jul 2013
Location: USA
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Run Capacitor, AC, outside blower, and a couple technical questions

Hello, been browsing around these forums and watching a few DIY videos on diagnostics/repair for AC units the past few days. After being quoted nearly 250 dollars minimum for visit/labor, I decided I'm just going to resolve it myself. Or try, anyway.

AC blower wasn't coming on.

Using a few of the tools and guides, I've become pretty certain it was the running capacitor in my blower that was the culprit.
-Inside unit comes on
-Checked breakers
-Contact doesn't attempt to engage
-No sound at all when thermostat is enabled
-Subsequently, no motor engage, even with manual 'stick' starting the fan

Not 100% on all terminology just yet, but I have a 'dual run capacitor' I'm replacing.

If I'm not mistaken, which is probable, it is most likely this part, which should be in the mail tomorrow. I have a diagram drawn of the wiring to the terminals and found an identical replacement. The capacitor I've removed doesn't seem to be dimpled or swelling anywhere, but the terminals are QUITE rusted and the part looks weathered.

The night before it went fubar, I was on my back porch, quite inebriated, and I heard a humming/buzzing sound intermittently, about every five minutes or so, but at the time I dismissed it as someone's cellphone vibrating. The obvious malfunction in the morning made me realize it had to be the outside unit, but that intermittent buzzing didn't come back.

Apologies for the excessive details, I'm just trying to be as thorough as possible, as I'm clearly no expert. My biggest question is, assuming it wasn't the running capacitor causing the malfunction, what is the most likely next problem? I have a voltmeter (experienced with) I'll test once the new part is fitted, and bring diagnostics back, I just want to know what I should/could possibly need to prepare for if it doesn't solve the problem. OR any other relevant help based on what I've provided.
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Old 07-09-13, 10:49 PM
PJmax's Avatar
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Welcome to the forums.

Ok.....if you're going to be doing your own repairs you need to get the parts named correctly.

"AC blower wasn't coming on" ....... the AC blower is inside the house in the furnace/air handler.
Outside you have the condensor fan and the compressor.

When the thermostat calls for AC.... the contactor should close outside starting the fan and the compressor. Even if the capacitor was bad the contactor would engage.

Normal diagnostics would be to check for 240 VAC on the input side of the contactor and 24VAC on the contactor coil. Once the contactor close if nothing happens you check for 240 VAC on the load side of the contactor.

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