A/C Unit Outside Not Coming On - HVAC - DIY Chatroom Home Improvement Forum


Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > HVAC

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Display Modes
Old 03-18-2011, 11:00 PM   #1
Newbie
 
Join Date: Mar 2011
Posts: 2
Rewards Points: 10
Default

A/C unit outside not coming on


Outside unit doesn't turn on. If I leave the thermostat set to Auto, the inside unit won't come on but if I turn the thermostat to On the inside unit blows (not cool) but the outside unit still doesn't come on.
Any suggestions as to where to start?
Thanks

Advertisement

Ksjka is offline   Reply With Quote
Old 03-18-2011, 11:39 PM   #2
Retired from the grind
 
gregzoll's Avatar
 
Join Date: Dec 2006
Location: Midwest - Central Illinois
Posts: 14,401
Rewards Points: 2,464
Default

A/C unit outside not coming on


Broken wire from the air handler to the outside condenser, tripped breaker, fuse disconnect outside corroded, or missing, corroded connections in the outside unit, blown fuse, or broken connection in the air handler. Those would be the best places to start.

Advertisement

gregzoll is offline   Reply With Quote
Old 03-19-2011, 12:00 AM   #3
I'm Your Huckleberry
 
Join Date: Mar 2011
Posts: 5,884
Rewards Points: 2,220
Default

A/C unit outside not coming on


Wait, the title of the thread says that only the outside unit won't come on. When you put the stat in the auto and cool mode and drop the set point (desired temp) really low (to make certain the system is calling to come one) what happens? Is the inside blower coming on at all or not?
Doc Holliday is offline   Reply With Quote
Old 03-19-2011, 02:34 AM   #4
Newbie
 
Join Date: Mar 2011
Posts: 2
Rewards Points: 10
Default

A/C unit outside not coming on


Quote:
Originally Posted by Doc Holliday
Wait, the title of the thread says that only the outside unit won't come on. When you put the stat in the auto and cool mode and drop the set point (desired temp) really low (to make certain the system is calling to come one) what happens? Is the inside blower coming on at all or not?
No. The inside blower doesn't come on if set to auto no matter what it's set at. It will come on if I switch it from auto to on though. It's night time so I haven't been able to check anything outside. The breaker isn't tripped though.
Ksjka is offline   Reply With Quote
Old 03-19-2011, 04:10 AM   #5
Retired from the grind
 
gregzoll's Avatar
 
Join Date: Dec 2006
Location: Midwest - Central Illinois
Posts: 14,401
Rewards Points: 2,464
Default

A/C unit outside not coming on


If it comes on when set to Fan, then call a reputable HVAC tech. Worst case scenario being that it is a weekend, it will cost you triple.
gregzoll is offline   Reply With Quote
Old 03-19-2011, 07:30 AM   #6
Member
 
Join Date: Mar 2011
Posts: 72
Rewards Points: 75
Default

A/C unit outside not coming on


from reading the post that was made whats different going on here!did it ever run right ,or did you just move there or how about this,did you just try to put a new thermostat on the system? The sequence of operation is like this: On the t-stat auto-on switch all that does is control your indoor blower motor.In the on position the blower motor will run 24 hrs a day.When the auto position is selected the blower motor will cycle off when the home reaches the desired temp thats selected. If the system wasnt giving you any problems before and nothing new has been done to it ,the outdoor unit still giving you a problem. When you select the desired temp you want, first thing youll notice is the inddor blower coming on.This will tell you the tstat is telling the system to go to work. If the outdoor unit isnt working the most common thing to do first is check the breaker at the main panel,if its on go ahead and reset it . No od unit still ,than ck the fuses in the dissconect,if fuses are good and you have power from the breaker,well you have a control problem with the low voltage going to the od unit.Now on one of your posts the fan doesnt come on in auto no matter what you set it on .but comes on when on is selected. That statement right there tells me the t-stat is defective due to not coming on in auto.since it comes on in the on position that tells me that the relays are ok.as a logical guess the t-stat might be your only problem.
1mastertech is offline   Reply With Quote
Old 03-19-2011, 07:38 AM   #7
Member
 
Join Date: Mar 2010
Location: PENNSYLVANIA
Posts: 2,258
Rewards Points: 1,044
Default

A/C unit outside not coming on


Do you have 24 volts outside when you turn the thermostat down with it in auto and cool. If not post back if so post back again and someone will walk you through it.
COLDIRON is offline   Reply With Quote
Old 03-19-2011, 07:42 AM   #8
I'm Your Huckleberry
 
Join Date: Mar 2011
Posts: 5,884
Rewards Points: 2,220
Default

A/C unit outside not coming on


To check to see if stat is bad: turn breakers off for both furnace and a/c unit (outside unit). You will need a small screwdriver to disconnect the red wire on the "R" terminal, the green wire from the "G' teminal and the either blue or yellow wire from the "Y" terminal at the thermstat. Twist all three of those wires together making certain they do not touch anything else whatsoever, and turn the breakers to both units back on.

r is 24 volts so power, g is for the fan and whichever wire is on the Y terminal, either blue or yellow, is cool (outside unit) so now all you've done is take away the switch (stat) and manually tell your system to go to cool. If it works, your stat is bad.

It is important to not let those wires touch anything and to shut off system by the breakers before you mess with any wires and then shut the system down by the breakers after youv'e twisted those wires together to check if system comes on (after turning breakers back on) or you stand a chance of blowing the fuse in the furnace.

Hope that helps. If nothing works this way you might be looking at a control board but this would be a good place to begin diagnostics as stats go bad regularly.
Doc Holliday is offline   Reply With Quote
Old 03-19-2011, 12:16 PM   #9
Member
 
Join Date: Feb 2011
Posts: 94
Rewards Points: 75
Default

A/C unit outside not coming on


Usually stats are the last thing to go bad, if it's in auto it won't come on until the cooling makes at the condensing unit. Low pressure switch open? Fuse blown? You will need a meter and check whats going on.
Hubcap626 is offline   Reply With Quote
Old 03-19-2011, 03:32 PM   #10
I'm Your Huckleberry
 
Join Date: Mar 2011
Posts: 5,884
Rewards Points: 2,220
Default

A/C unit outside not coming on


Quote:
Originally Posted by gregzoll View Post
If it comes on when set to Fan, then call a reputable HVAC tech. Worst case scenario being that it is a weekend, it will cost you triple.

We don't charge any different for the weekends. Nights and odd hours, yes. Weekends, normal rate.
Doc Holliday is offline   Reply With Quote
Old 03-19-2011, 11:12 PM   #11
Member
 
Join Date: Mar 2011
Posts: 72
Rewards Points: 75
Default

A/C unit outside not coming on


Ok I was thinking about a residential application and not a commercial tstat.On a residential stat the auto modes for the blower only.It has nothing to do with the outside unit coming on.The blower will come on as soon as theres a call for cooling.This post says Im a newbie to this site,far cry from a newbie in the field>Not a Know-it-all but not an green horn either.Its not my first rodeo !
1mastertech is offline   Reply With Quote
Old 03-19-2011, 11:32 PM   #12
I'm Your Huckleberry
 
Join Date: Mar 2011
Posts: 5,884
Rewards Points: 2,220
Default

A/C unit outside not coming on


Quote:
Originally Posted by 1mastertech View Post
Ok I was thinking about a residential application and not a commercial tstat.On a residential stat the auto modes for the blower only.It has nothing to do with the outside unit coming on.The blower will come on as soon as theres a call for cooling.This post says Im a newbie to this site,far cry from a newbie in the field>Not a Know-it-all but not an green horn either.Its not my first rodeo !

All stats have everthing to do with the a/c unit coming on. Auto and cool. They have no idea where they are being installed, commercial or resi, and for the most and simplist part are the same.

Last edited by Doc Holliday; 03-19-2011 at 11:43 PM.
Doc Holliday is offline   Reply With Quote
Old 03-19-2011, 11:37 PM   #13
I'm Your Huckleberry
 
Join Date: Mar 2011
Posts: 5,884
Rewards Points: 2,220
Default

A/C unit outside not coming on


And let's not forget than many regular split systems (and a few package units) you'd find in homes are installled in light commercial. e.i, offices.

I can take my stat from my house and walk down the street to the commercial business park, remove their stat and put mine on and the system will work. Split or package any size. I can take their stat and install it in my place just as easily.

I'd have to make sure the stats were set for either electric or gas if applicable but that's about as far as that goes.
Doc Holliday is offline   Reply With Quote
Old 03-19-2011, 11:44 PM   #14
I'm Your Huckleberry
 
Join Date: Mar 2011
Posts: 5,884
Rewards Points: 2,220
Default

A/C unit outside not coming on


All a stat is is a switch, nothing much more than that. Controlled by low voltage. By turning a stat to "on" or to "auto" and "cool" or to "auto" and "heat" or simpy "off" you tell the stat where you want that low voltage to go or not go.

Last edited by Doc Holliday; 03-19-2011 at 11:47 PM.
Doc Holliday is offline   Reply With Quote
Old 03-20-2011, 12:12 AM   #15
Member
 
Join Date: Mar 2011
Posts: 72
Rewards Points: 75
Default

A/C unit outside not coming on


I agree but the execution of a low voltage command is being looked at differently and there is a difference.On a stat the auto on featutre controls the blower only and has nothing to dowith the outdoor ac.Theres a stat that has a auto feature that wikll run the heating and cooling so a customer doesnt have to manually change modes to get the system to heat or cool.Its called an auto changeover tstat.Im confident that we know whats going on but are looking at it at different applications.If I cant work a stat aftyer 30 yrs in this trade well ill hang my tools up!

Advertisement

1mastertech is offline   Reply With Quote
Reply


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
What is the price difference between a 2.5 ton unit and a 3 ton unit? Leoskee HVAC 5 06-12-2014 01:00 PM
HEIL/ICP gas/electric self-contained unit -- blowing cold air, won't shut off AboveTheBULL HVAC 3 06-28-2010 07:23 AM
Why is water coming out from the bottom of the HVAC unit? Woz HVAC 11 08-02-2009 09:38 AM
Central Air Outside Unit Cover czars HVAC 2 01-07-2009 11:23 PM
Electric question from power pole to unit Slocalaman Electrical 3 11-06-2008 04:23 PM




Top of Page | View New Posts