Home AC Question - Bad Float Switch?

[Jim Moore]

Hi Guys,

My home AC is cutting out occasionally, doing exactly what it would do if the drain was clogged and the float switch was activated. Except the drain is not clogged. I think I have a bad float switch instead. I THINK I can check it next time the AC cuts off by checking for continuity across the switch. If I have an open AND my drain is not clogged that means a bad switch, right?

If my switch is bad I can replace it by simply cutting the wires going to the switch and wiring in the new switch. Nothing tricky there, right?

 

[Shinyribs]

Turn the breaker off to the outside unit if you do this. I've seen folks fiddling with these switches and beat the poor unit to death turning it on and off every 2 seconds.

And yes, wiring in a new switch is easy as that. It's low voltage (24v) so it won't shock you, but turn the breaker off anyway. It would suck to accidentally short a wire to the cabinet and zap the transformer. On any modern unit ( past 10-15 yrs) there should be a 3amp fuse to safeguard the transformer, but you can't rely on that.

You say it's cutting out occasionally. You mean the outside unit, or the whole system indoors and out?

 

[Jim Moore]

Turn the breaker off to the outside unit if you do this. I've seen folks fiddling with these switches and beat the poor unit to death turning it on and off every 2 seconds.

And yes, wiring in a new switch is easy as that. It's low voltage (24v) so it won't shock you, but turn the breaker off anyway. It would suck to accidentally short a wire to the cabinet and zap the transformer. On any modern unit ( past 10-15 yrs) there should be a 3amp fuse to safeguard the transformer, but you can't rely on that.

You say it's cutting out occasionally. You mean the outside unit, or the whole system indoors and out?

The entire system shuts off, but the display on the thermostat still works.

 

[Shinyribs]

Ok, if the entire system cuts off it is most likely the switch like you suspect. You may have batteries in your tstat to keep it powered.

Only reason I asked was because sometimes the outdoor fan can be failing to start/run intermittently and that's an easy to way to cook a compressor. Don't see the fan running so you assume it's off, and the little compressor is in there just screaming for help 😁

 

[FLrider]

In that case you may need a new capacitor or two depending on how old the ac is. Newer ac‘s have a single dual function capacitor. One side runs the fan, the other the compressor . When they are swollen they are toast so it is easy to tell.. just my 0.02 cts

 

[Jim Moore]

In that case you may need a new capacitor or two depending on how old the ac is. Newer ac‘s have a single dual function capacitor. One side runs the fan, the other the compressor . When they are swollen they are toast so it is easy to tell.. just my 0.02 cts

yeah, I'm hip to the bad capacitor problem. This definitely isn't that, although I've swapped out a few. Thanks though.

 

[Shinyribs]

In that case you may need a new capacitor or two depending on how old the ac is. Newer ac‘s have a single dual function capacitor. One side runs the fan, the other the compressor . When they are swollen they are toast so it is easy to tell.. just my 0.02 cts

Some units are coming with hard start kits on them now, which is basically another start capacitor downstream of the normal capacitor. They're in cases that prevent you seeing visual clues of damage, and I've never seen one swell. When they die the terminals melt.

You would think the normal capacitor could still start the compressor, but it won't. The hard start is sapping the energy the capacitor is releasing rather than sending it to the compressor. You'll get a short grunt from the compressor and that's it. Something to look out for before swapping capacitors out.

 

[FLrider]

I guess it all depends on the brand/system you have. Our Carrier has a dual capacitor that does swell up when it goes, the Lennox in our old house did he same. So many different systems…🤔

 

[Jim Moore]

I've seen them swell as well. The last one was swollen and had a dead garter snake wrapped around the contacts.

 

[Shinyribs]

I guess it all depends on the brand/system you have. Our Carrier has a dual capacitor that does swell up when it goes, the Lennox in our old house did he same. So many different systems…🤔

Yes sir, 99% of the time a standard canned cap will swell, metal or plastic can. It's the additional hard start caps that piggyback those that don't swell to give you a visual clue, and will cause the machine to act like there's a failed main cap when it's actually fine.

 

[Jim Moore]

Thanks again guys. I got a new float switch from Amazon, but (of course) the AC has been working perfectly since I started this thread. I'm not going to try the new one until it acts up again. I'll let you know when that happens.