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Message
A/C on but not cooling sometimes
Posted on 7/18/24 at 11:14 am
Posted on 7/18/24 at 11:14 am
Almost on a daily basis my upstairs AC unit will kick on but will not cool and if I don't catch it quick enough it gets really hot and hard to cool back down. If I turn off the unit at the thermostat and turn it back on it starts working fine, every time. I have noticed when it is not cooling, but running, the fan on the outside unit isn't moving. When I turn it off and back on, the fan spins on the outside unit and everything is fine. I have had AC techs come out twice and they have blamed it on my Nest Thermostat. Do I just need to replace the thermostat or could it be something else? It's a 3 ton Lennox and its about 3 years old. I also have a Nest on my downstairs unit and this never happens.
Update: After two trips from the AC company, two days in a row, the issue seems to be fixed. Contactor was "welded shut". Without completely ripping the people that came out, I basically had to force them to change the contactor on the unit. Thanks to the H&G board for helping me on this or I would probably still be dealing with the issue
Update: After two trips from the AC company, two days in a row, the issue seems to be fixed. Contactor was "welded shut". Without completely ripping the people that came out, I basically had to force them to change the contactor on the unit. Thanks to the H&G board for helping me on this or I would probably still be dealing with the issue
This post was edited on 8/8/24 at 9:08 pm
5
Posted on 7/18/24 at 11:23 am to thatguy777
quote:
I have noticed when it is not cooling, but running, the fan on the outside unit isn't moving.
Sounds like either a bad condensor dual run capacitor (fan side of the capacitor is weak) or a failing condensor fan motor. Do you by chance hear a high pitched sound from the condensor fan motor when it is operating? Anyway, it’s not uncommon for the bushings in the condensor fan motor to fail with age. If the fan motor, best to change the capacitor at the same time the fan motor is replaced.
Posted on 7/18/24 at 11:35 am to CrawDude
Nope, when it's running it sounds completely normal and everything looks and sounds good.
Posted on 7/18/24 at 11:36 am to CrawDude
Also possible that your contactor is having problems sucking in the contacts. Contactor and cap are not hard to replace and are cheap, I would start there.
If you are electrically inclined you can check the control voltage on the contactor (the small wires that connect on either side) when the ac is turned on but the fan is not running. If you see 24V there then check the voltage on the motor side of the contactor. If you see 0v you know it’s a bad contactor. If 240v that’s not the problem. Keep in mind you’re measuring exposed voltage though, so no touchy of course. That’s a cheap and easy thing to do first before calling someone out.
If you are electrically inclined you can check the control voltage on the contactor (the small wires that connect on either side) when the ac is turned on but the fan is not running. If you see 24V there then check the voltage on the motor side of the contactor. If you see 0v you know it’s a bad contactor. If 240v that’s not the problem. Keep in mind you’re measuring exposed voltage though, so no touchy of course. That’s a cheap and easy thing to do first before calling someone out.
Posted on 7/18/24 at 11:40 am to thatguy777
It could be the thermostat failing. I have read in several forums that HVAC techs are not wild about Nest thermostats.
Do you have an old thermostat handy to test with?
But, I would think it is the capacitor or the contactor.
Do you have an old thermostat handy to test with?
But, I would think it is the capacitor or the contactor.
This post was edited on 7/18/24 at 11:47 am
Posted on 7/18/24 at 11:41 am to thatguy777
At 3 years old it should be under warranty.
I will say that Nest has a lot of issues, that very well maybe the case. I know plenty of people that like them a lot though.
But personally if the techs say that, I'd consider buying the cheapest thermostat from the hardware store and testing that out. If it stops you know the problem, if it doesn't stop call the AC installer back its probably a failing part.
I will say that Nest has a lot of issues, that very well maybe the case. I know plenty of people that like them a lot though.
But personally if the techs say that, I'd consider buying the cheapest thermostat from the hardware store and testing that out. If it stops you know the problem, if it doesn't stop call the AC installer back its probably a failing part.
Posted on 7/18/24 at 12:00 pm to thatguy777
OK, I missed the 3 years old unit - so it not likely the fan motor. But capacitors fail all the time, even on newer units. I agree with others on the Nest thermostat comments - the techs on professional HVAC forums I follow hate them as they can cause weird issues that can actually potentially cause significant damage to HVAC system. There are Honeywell & Ecobee thermostats can do the same things as a Nest without the potential issues.
If you are not a DYIer comfortable with changing capacitors, contactors or thermostats it would be best to call a tech - should be easy problem to troubleshoot. Don’t turn an “inexpensive” repair into a big one.
If you are not a DYIer comfortable with changing capacitors, contactors or thermostats it would be best to call a tech - should be easy problem to troubleshoot. Don’t turn an “inexpensive” repair into a big one.
This post was edited on 8/8/24 at 11:07 pm
Posted on 7/18/24 at 12:05 pm to CrawDude
I am not married to the nest and not even that big of a fan of it, I just like the ability to change the temperature settings from the app on my phone.
Posted on 7/18/24 at 12:06 pm to thatguy777
quote:
I just like the ability to change the temperature settings from the app on my phone.
You can do the same with Honeywell and others.
Amazon has a cheap wifi thermostat that is made by Honeywell.
Amazon Thermostat
Entergy Lousiana will basically give you the Amazon Thermostat for free or a discount on other thermostats.
Smart Thermostats Entergy Lousiana
I have the Honeywell T9 and I love the use of the remote sensor.
This post was edited on 7/18/24 at 12:10 pm
Posted on 7/18/24 at 12:57 pm to gorillacoco
Oh yeah, if you check the control voltage when the ac is running and it’s 0v, you know it’s something upstream, maybe the thermostat or the board (or maybe the pan in the attic is full, it’s possible for that float switch to toggle on/off if it’s draining very slowly).
If you check the control voltage and it’s good, and the contactor is also good (240V on downstream side) then you have a fan issue or you have a capacitor problem. Capacitor is cheap and easy to replace but the terminals can carry charge and shock you even when disconnected from a power source so handle carefully even once removed if you choose to go that route.
If you check the control voltage and it’s good, and the contactor is also good (240V on downstream side) then you have a fan issue or you have a capacitor problem. Capacitor is cheap and easy to replace but the terminals can carry charge and shock you even when disconnected from a power source so handle carefully even once removed if you choose to go that route.
Posted on 8/8/24 at 9:07 pm to thatguy777
Update: After two trips from the AC company, two days in a row, the issue seems to be fixed. Contactor was "welded shut". Without completely ripping the people that came out, I basically had to force them to change the contactor on the unit. Thanks to the H&G board for helping me on this or I would probably still be dealing with the issue
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