Came home and house was warm. Air was just cool out of the vents while the AC was kicked on. We've outside and the outside unit fan wasn't spinning and the pipe was obviously warm to the touch and not sweating.

Turned unit off and waited 30 minutes. Turned thermostat back on and went outside to wait and watch the condenser unit outside. I heard and saw the fan click on and start to spin and then it immediately turned off.

Thoughts?

Probably low pressure. There are safeguards to keep the compressor from burning up. My guess is a coolant leak.

aggie_wes said:

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Probably low pressure. There are safeguards to keep the compressor from burning up. My guess is a coolant leak.

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That would suck. This unit had that issue 2 years ago and I was told they discovered it was low on Freon and leaking from a connection point in the line. $700 and 4lbs of Freon and all was well.

Since the condenser fan starts but then cuts out, it might be a couple of things other than a low refrigerant condition that triggers a shut-down sensor.

1. Failing capacitor - causes fan to draw too much current and that trips the fan's internal overload
- replace capacitor (cheap fix)

2. Failing fan -- bearings will begin to drag and once again cause fan to trip out on its internal overload
- replace fan motor (semi-cheap fix)

3. Failing contactor -- contact points pit and burn and no longer provide low-resistance (or any) current path to both fan and condensor
- replace contactor (cheap fix)

If a coolant leak -- ask the 'tech' to find the damn leak and repair it. Unfortunately, some of these guys make easy money by doing the 'gas and go' method, and it sounds like they charged you plenty last time just to re-charge.

BTW, HVAC companies are having a helluva time getting and keeping competent help. As a result, some marginal guys are being put in trucks and sent out.

Good luck.

Did you happen to hear if the compressor came on too or just the fan?

Depending on the age and model of the unit it could be a capacitor which is an easy fix or it could be a bad motor especially if it's low voltage commutated.

Best thing to do is visually inspect the capacitor and if the lid looks swollen or dome shaped then you likely found your culprit.
It could also be refrigerant being low and such but a lot of times after storms and such we find a lot of bad capacitors.

Good luck, keep us posted!

BenTheGoodAg said:

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Blown Capacitor? They're easy to check for a bulging top. Just don't touch the leads.

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Fan usually doesn't kick on at all if it's a capacitor. OP said fan came on, but then shut off.

Unit was replaced in 2017, so it's not that old. I'm definitely going with a different company this time then the one 2 years ago that charged me for freon for sure. I can remember at the time he said he actually found and fixed the leak.

To answer sometimes question, I'm honestly not sure if the compressor kicked on when I was outside. I almost want to say it didn't. When the fan wasn't spinning or when it turned on and immediately turned back off, the unit was silent.

We did have really bad storms with bad lightning a few days ago. Not sure if that's related. AC has been working fine though and was working when we left the house last night for a function at my daughter's school. Came back and immediately noticed the house felt warmer. Could tell the air coming out of the vents was just "barely cool" when the thermostat was showing the AC was on.

Of possibly greater concern, when I was up in the attic I noticed this burned area where the gas furnace meets the start of the ductwork. Almost looks like fire damage?? Could this have been from a lightning strike?? We've had some bad storms in the last few weeks with lightning but when I looked up at the area above this in the attic, I didn't immediately notice a hole or damage in the roof. It was night though, so it's possible I didn't notice something. We've also had probably 2 to 3 inches of rain in the last week or so, so I'd think I would have pretty significant water damage around this area but I didn't see anything noticeable. There are lots of black charred fragments everywhere as you can kind of see in the picture on top of the furnace

Maybe it's a blessing in disguise that I'm having to call an HVAC company out so they can look at this area as well. I don't like the look of it at all.

Cromagnum said:

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BenTheGoodAg said:

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Blown Capacitor? They're easy to check for a bulging top. Just don't touch the leads.

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Fan usually doesn't kick on at all if it's a capacitor. OP said fan came on, but then shut off.

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Not true of all units, capacitor can be bad and fan runs

Is the black insulated pipe just out of the frame the refrigerant line that goes to the outdoor unit? If so I would say the burn mark was a result of when they were installing the coil and the torch got pointed the wrong way.

Historically when I've seen units struck by lightning it's the flue pipe through the roof that gets hit, the unit will not run at all inside or out and you'll find burn marks in the unit where the ground wire connects or behind the circuit board after removal. I'm guessing that's a Goodman or Amana system as they had a coil that the refrigerant lines came out of the top (assuming that photo was the top).

I'm going to lean toward a capacitor being bad but my advice is worth what you paid.

Good luck!

FDXAg said:

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Of possibly greater concern, when I was up in the attic I noticed this burned area where the gas furnace meets the start of the ductwork. Almost looks like fire damage?? Could this have been from a lightning strike?? We've had some bad storms in the last few weeks with lightning but when I looked up at the area above this in the attic, I didn't immediately notice a hole or damage in the roof. It was night though, so it's possible I didn't notice something. We've also had probably 2 to 3 inches of rain in the last week or so, so I'd think I would have pretty significant water damage around this area but I didn't see anything noticeable. There are lots of black charred fragments everywhere as you can kind of see in the picture on top of the furnace

Maybe it's a blessing in disguise that I'm having to call an HVAC company out so they can look at this area as well. I don't like the look of it at all.

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Yes that's the refrigerated line I believe. It has that wrapped pipe plus a thin copperlooking pipe next to it that follows exactly next to it.

Only thing that bothers me is I don't believe this looked this way when I was up here months ago. The gas furnace is the original unit to the house and I've been up here numerous times and pretty sure I would have noticed this burn mark before.

Quote:

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If so I would say the burn mark was a result of when they were installing the coil and the torch got pointed the wrong way.

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Agreed. I've heard it happens even in the best of families.

Well crap, this problem continues to resurface and no AC company can figure out what's going on. It'll be fine for days/weeks and then randomly house warms up and I go outside and the unit outside is completely quiet and the fan is not spinning. At least 3 or 4 times since this original post in April the unit has randomly stopped cooling. And pretty much every time it is in the late evening (usually when my wife is cooking with the oven on, coincidentally) I've had multiple service calls during this time and no one can find the problem. Eventually the AC just starts working again.

Usually turning both thermostats off for 30 minutes or so will somehow reset the system and then we can turn it on and it'll start cooling again. But of course today that's not working.

They say it is full of freon. They say they can't see anything obviously wrong when they hook up their equipment and look at readings. One guy mentioned it might be an electrical "gremlin" but electrical issues can be tough to figure out he said. Each time I've had someone out they can't find a specific part of piece that's failing. Usually by the time they've come out, the unit starts working again. I'm just upset because I need a consistently working AC and I'm worried that even replacing a bunch of parts won't fix it because no one knows what's going on. The AC was replaced in 2017, so about 7 years ago.

Everything online points to either low freon or maybe the capacitor(s) being bad. There's 2 on the unit, one outside and one on the inside. Both have apparently been tested and test fine. Visually I can tell neither are bulging. The pipe outside is not frozen when the unit doesn't work. And when it stops cooling, I don't hear the hum of the compressor when the fan blades aren't spinning. Seems like the whole outside unit is just off or shut down. Most videos online indicate if the capacitor is going bad, you'll go outside and the fan blades won't be spinning but you'll hear the hum of the compressor. Not the case here.

Tonight we waited an hour and turned the thermostats back on. I'm outside standing next to the unit and I hear the click of the fan blades and compressor start to turn on and the fan blades start spinning, and then within a second there's another click and it turns off. As if the system is forcing itself to shut off instantly.

FDXAg said:

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Came home and house was warm. Air was just cool out of the vents while the AC was kicked on. We've outside and the outside unit fan wasn't spinning and the pipe was obviously warm to the touch and not sweating.

Turned unit off and waited 30 minutes. Turned thermostat back on and went outside to wait and watch the condenser unit outside. I heard and saw the fan click on and start to spin and then it immediately turned off.

Thoughts?

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Mine stopped working tonight, too. HIGH FIVE!!!!

Could be failing capacitors, or maybe bad float switch, or slow drain that causes float switch to trigger then reset once it drains down from not running. Also could be a control board failing. What brand is the hvac ?

They say my capacitors show good and the float switch isn't the issue. Drains are clear. Outdoor unit is a Lennox. Basic 1 stage 5 ton unit. 7 years old now.

Guy that came back today says he feels it's either the contacts occasionally not properly functioning with the wire that switches and sends power to the unit from the thermostat (although he hasn't actually seen it not work yet and the contacts visually look fine) or the fan motor is having an issue that occasionally just causes it to stop running and then of course that breaks the circuit and cuts power to the compressor to keep it from overheating. He said it's rare but he's seen it before a couple times over the years. All the numbers on his meters show in correct range when the unit is running and he said the power draw looks normal and is nowhere near the level of activating thermal overload or causing the system to shutdown to prevent damage/overheating.

He didn't want to throw parts at it yet and replace both the fan motor and the contacts, so he told me a way to hopefully tell which is the issue when/if I notice the house warming up and the unit outside not running again.

This is the 3rd time this company has been out and no service fee on these last couple visits because they haven't been able to pinpoint the issue yet. It's back to running and cooling now, at least. House got up to 86 earlier this afternoon and was miserable.

We'll see....

Are your thermostats all 100% wired? As in, you don't need any batteries for them right?

No, they are a very old style that are only battery powered..... Don't have a place for common wire. I'm upgrading those this week

FDXAg said:

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No, they are a very old style that are only battery powered..... Don't have a place for common wire. I'm upgrading those this week

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This could be your problem. Are the batteries brand freakin new? If not, make it so and see what you get.

Batteries are replaced. No change. Today we got another clue. Looks like the outside unit is fine. I can manually engage the contactor and it immediately fires up. And it will cool just fine as long as I manually keep that contactor depressed and engaged. But noticed that it appears the signal is intermittent from the thermostat, so I suppose that could mean the actual wires are compromised or the control panel maybe?

When the thermostats are calling for cool on, only sometimes is that properly sending signal to depress the contactor on the outside unit. Good thing is that should mean the outside unit is ok but still doesn't narrow down the problem yet.

What brand hvac ?

The intermittent sure makes me lean to a failing control board. I have seen this happen a few times on a york and a goodman and also once on a carrier.

Yes. That's among the lines of why I asked about the batteries. I think you're onto it. Maybe the wires are just loose?

Manually operating the contactor doesn't completely rule out the contactor. It does show that the high voltage components (capacitor, fan and compressor) are good. The contacts can still be bad and the coil could be bad. Under normal operation you could check to see if the contactor coil is receiving a 24V signal. If the coil does see 24V then check if there is any voltage drop across the contactors. If there is a voltage drop then the contacts are bad. If the contactor checks out OK then I would move on to checking to see if the thermostat is bad.

This might have been suggested before, but check the wires and contacts. A slightly poor connection can cause voltage drop and then trip.

I've repaired an old college HCAC that the contactor wasn't 100%. Literally cut the end and redid the connection and helped on arcing issue when hot.

~egon