HVAC Fan Won't Turn On

"ttyymmnn" (ttyymmnn) 03/11/2016 at 12:14 • Filed to: None

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I noticed yesterday that the AC wasn’t coming on in my house. We had a big electrical storm the other night, and I know that one of the GFCI sockets in the kitchen popped and had to be reset. I checked the breaker in the garage that controls the attic unit and it was not tripped. I turned it off and on anyway. I checked the large breaker outside for the compressor. It was not tripped, but I cycled it anyway. I can hear the thermostat click to start the process, but nothing happens. I have a compressor outside, and a blower/gas heater in the attic. Any ideas?

EL_ULY > ttyymmnn 03/11/2016 at 12:23

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Capacitor time? Or the fan could of when bad. One of the 4 wires going into the thermostat is for the fan, check that as well

ttyymmnn > EL_ULY 03/11/2016 at 12:25

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Mas info, por favor. Is that out in the compressor?

RamblinRover Luxury-Yacht > ttyymmnn 03/11/2016 at 12:29

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Could be your motor starting setup in the attic is fried. A blown capacitor, for example. Electric motors require a degree of control over how they start above a certain size, and if the starting caps are fried, they don’t get the initial surge of current to actually start. Or any current at all, depending. If you have a multimeter and can get to the wiring, it may make sense to see if you have power getting to the motor with thermostat on. Or if the thermostat’s contacts might be bad.

tl;dr: Wacky surges in current can disable electric motor devices. Not the motor itself, but something *on* the motor. Can also be other things, however.

EL_ULY > ttyymmnn 03/11/2016 at 12:30

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yes, you remove the service panel. You can usually tell if the are bad if the cylindrical shape of it seems bloated/warped. I’d check that wire first. it runs from the thermostat all the way into the outside condenser/compressor. If refrigerant is low, it will not kick on as well.

Thinking about it more, THESE go bad quite often as well. Check this as well.

ttyymmnn > EL_ULY 03/11/2016 at 12:31

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Thanks. Is there any way to test the part to see if it’s shot?

EL_ULY > ttyymmnn 03/11/2016 at 12:33

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In the center of the contact switch there should be a test button. You can press it with a screw driver

ttyymmnn > EL_ULY 03/11/2016 at 12:34

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I had taken the thermo off the wall for painting, but it has worked since I put it back up. I did check today to make sure the wires were still in place, and they are.

EL_ULY > ttyymmnn 03/11/2016 at 12:34

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just press down

ttyymmnn > EL_ULY 03/11/2016 at 12:35

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Do you make house calls?

EL_ULY > ttyymmnn 03/11/2016 at 12:36

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These contact switches are very sensitive to water

EL_ULY > ttyymmnn 03/11/2016 at 12:37

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i used to :] My dad has a large commercial A/C company but for a while, he took residential work with me :]

jariten1781 > ttyymmnn 03/11/2016 at 12:46

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Yup, like EL_ULY said it's most likely your starting cap. Super easy to replace. Happens in Spring all the time...majority of AC repair calls this time of year are for it.

ttyymmnn > jariten1781 03/11/2016 at 12:50

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When you say “starting cap” do you mean capacitor? Are you all talking about the same part?

TheRealBicycleBuck > ttyymmnn 03/11/2016 at 12:52

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There is a capacitor that gives the system enough juice to fire. It may be popped ( if you’re lucky). You will want to hurry and check since the hvac supply places are usually closed on the weekends.

Replacing a blown cap and even the motor are pretty easy. I'd link you back to my post where I bragged about doing this last Labor Day weekend, but I'm on mobile right now.

ttyymmnn > TheRealBicycleBuck 03/11/2016 at 12:58

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They wouldn’t carry something like this at my local Home Despot?

DoYouEvenShift > ttyymmnn 03/11/2016 at 13:10

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I have a Trane HVAC in my house. Last summer the same thing happend to mine. Eveything gets power, outside unit comes on but no blower. After some diag work, I found the contacts on the relay burned through on the back of the main circuit board. $180 for a new one from an HVAV supply.

DoYouEvenShift > EL_ULY 03/11/2016 at 13:15

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I had that little guy go out on me too. Easy to tell in my case, it was crispy!!

jariten1781 > ttyymmnn 03/11/2016 at 13:32

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Yep, well at least initially, he started going through other stuff I wouldn’t check until I’d replaced the cap. Any time one won’t start I just replace the cap, it’s essentially a wear part that will die sooner rather than later so a prophylactic replacement is never wasted.

Sometimes it’s clearly visible in bulging.

Failed left, New right.

EL_ULY > DoYouEvenShift 03/11/2016 at 13:43

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Small bugs/animals are usually to blame. Fully intact lizard skeletons are so rad seeing on these :]

DoYouEvenShift > EL_ULY 03/11/2016 at 13:55

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Thats probably what it was, living in FL you cant take 2 steps outside without seeing 3-4 of those things scurry around.

ttyymmnn > jariten1781 03/11/2016 at 13:55

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And that will be found in the compressor outside? Also, I'm assuming that the large breaker outside labeled AC will need to be turned off before fooling around inside the compressor.

TheRealBicycleBuck > ttyymmnn 03/11/2016 at 14:00

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Nope. And to answer your other question, yeah, caps are capacitors.

http://oppositelock.kinja.com/i-fixed-a-thin…

http://oppositelock.kinja.com/just-my-luck-u…

Just be careful to make sure your replacement parts match the old parts, especially the fan motor if that needs to be replaced. Get the wrong motor and it will burn up before the end of the summer.

jariten1781 > ttyymmnn 03/11/2016 at 14:04

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Yep, I usually flip the breaker in the house panel and flip the outside (or remove fuses outside if it’s older). Leave it for a bit to allow the cap to discharge. It’ll be under the service panel if there is one and usually has a bracket you have to unscrew. Ideally you’d want to use plastic tools since the cap can store power even with it all shut off but, since I don’t have them I just wear gloves and be particularly meticulous...never any issues.

Here’s an inside shot, it also shows the contact switch others were talking about the cap is the cylinder on the right (that’s a three prong, there’s also two prong ones) :

ttyymmnn > jariten1781 03/11/2016 at 14:08

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Looking at EL_ULY’s post, is that contact switch something to replace or just reset?

Thanks for the awesome comment. I really appreciate all the excellent info I’m getting here.

jariten1781 > ttyymmnn 03/11/2016 at 14:11

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Don’t know...I’ve never seen one go out. If it was all charred up I’d buy a new one, but I’m not sure if that’s wasting money or not...I just tend to throw parts at things. I’ve fixed ~30 of these things for myself/friends/family/landlords, but I’m not trained or anything. Just a dude with some experience haha.