[N/A] A/C Issues

[ARFlyer]

I swear stuff breaks in threes....

Last night I got a notification from my thermostat that even after calling for A/C the house was heating up. I measured the air temp out of one of the registers and saw it was blowing 80°on a 70° evening.

Thankfully, my first thought was to check the outside condenser. I found it making a horrible electric hum with the fan not turning. I also noticed even a few feet away that I could feel heat coming from the unit. The whole unit was almost to hot to touch. I cycled the thermostat from
my phone which was a horrible mistake. As soon as the fan tried to kick back on something shorted out and started smoldering.

I'm thinking the fan motor snap an axle or its bearings. I hope I didn't fry the compressor in the process.

What do you guys think?

 

[Matthew]

You could connect a garden hose mister or sprinkler and water cool the outside coils, that might give you an idea if the cooling system is working. I'm not sure what would happen if the cooling fan only fails, the refrigerant would stay hot as it moved into the house and the evaporator. I don't know if it would "boil off" before the evaporator and not do any good. The compressor might still be OK, but a pressure gauge might the the only way to know for sure.

 

[denverpilot]

The smoldering could have been from something as simple as the starter capacitor blowing up, or a burnt/stuck relay, to the motor windings burning.

Nearly every place will try to sell you a new complete unit. There’s no profit margin in repairs for anybody in HVAC anymore.

Find someone who knows how to troubleshoot it and buy them beer. The parts to repair some problems are super cheap. Other parts like the compressor and maybe the fan motor, aren’t.

A stalled fan motor from a bad bearing or similar would draw a lot of current. It’s supposed to trip the outdoor breaker that’s feeding it but the little capacitor or relay/“contactor” often give up first. Or even the wiring between the input and those items can become a fuse. Pop.

Kill all power (not at the t-stat, at the outside disconnect or breaker) and see what’s jammed mechanically if anything. Deal with that first. Then see what smoked. Might be a cheap call to Grainger or might be a goner. Can’t tell until you open it up and look around a bit.

Wouldn’t worry about the heat thing. That likely indicates that the compressor was working and pumping coolant around and there was just no fan removing it from the loop. If the pressure relief didn’t dump all the coolant, you’re likely fine there.

But like I said, find an HVAC guy who needs beer. A company truck HVAC person will almost always try to sell you a new outdoor unit. When all you needed was a new motor because the bearings are permanently installed or similar, and a replacement relay to turn it on.

Check mechanical motion, fix. Then find the burnt crispy critter in the electrical. If the motor itself burnt your nose will know it.

This is all assuming it’s an older non-heat pump nothing-fancy outdoor unit. They get more complex to troubleshot if it’s a heat pump / high efficiency thing.

 

[Art Rose]

Age of the unit? Simple dx split? Variable speed? Heat pump? Kinda difficult to diagnose without additional basic information. It's making a horrible hum? From where? It's smoking. From where? There's no start capacitor in the condensing unit unless it has a hard start kit, and hard start capacitors tend to explode when they fail. Want a wild ass guess without important diagnostic information? It sounds like its likely a bad run capacitor for the condenser fan. Chances are that's a dual capacitor (silver round, or oval can with wires plugged into the top) which serves both the compressor and the fan. Turn the power off (verify), and look to see if it's swelled, or leaking. If it is, that's likely your problem. Otherwise, if the unit is a simple split, it could be a bad fan motor, something physically stopping the fan motor from turning, bad starter contactor, bad compressor, bad hard start capacitor, or a supply voltage issue. If it's come to the point of smoking without tripping a breaker, I'd also want to check wiring and breaker sizing. Residential units are honestly dirt simple, but if you lack basic knowledge, it's usually best to bite the bullet and call one of the residential Bubbas.

 

[PaulS]

Open the electrical panel on the condenser and look. Probably the start capacitor. Because you let the smoke escape it should be easy to see if it's junk. If that's it, make sure the power is disconnected, snap a pic of how it's wired, short the terminals with a screwdriver to make sure there is no stored charge, get the numbers off the side of the cap, plus the numbers off the condenser itself. Call an hvac supply house, buy a new one, install and run it. Don't get electrocuted.

 

[Art Rose]

Once again, there's no "start capacitor" in the condensing unit, unless it's a hard start kit capacitor. The capacitor, or capacitors, in the condensing unit are "run capacitors". The replacement capacitor can have a higher voltage rating, (never lower), and the micro farad rating must be within plus or minus 6% (rule of thumb) of the original. Ebay or Amazon. If you don't know what you're doing, or don't have a knowledgeable helper, leave this to the paid Bubba. A charged capacitor will light you up if you don't know what you're doing. And, shorting the capacitor with a screwdriver to discharge is common, but a bad practice that can damage the capacitor. By the way, in a pinch, capacitors can be wired in series, or parallel, depending, to achieve an acceptable range.