Quantcast

Thermostat clicks but nothing happens

Help Support House Repair Talk:

o2284200

Member
Joined
Oct 22, 2012
Messages
221
Reaction score
11
Hello all!

A/C has been running fine until last night. The thermostat clicks but nothing happens; neither the outside fan nor inside fan turn on. Fans will also not turn on, if switched to "On", instead of "Auto". I checked breaker, still on...I turned it off, waited 30 seconds, turned it back on, which did not help. FWIW, I also put fresh batteries in and cleaned connections about one month ago.

Your thoughts are greatly appreciated, thanks!
 

doechsli

Well-Known Member
Joined
May 29, 2012
Messages
68
Reaction score
23
I would say a starter cap, but I believe the furnace/air handler fan would run regardless of a cap failure. I just had one of these failures this year.

Another question is the "light switch" to control power to the furnace/air handler. My three year old grandson turned that off once unknown to my son. Typically around here they are mounted on the furnace/air handler.

Just guesses......good luck.
 

o2284200

Member
Joined
Oct 22, 2012
Messages
221
Reaction score
11
What is a "starter cap"? How does one troubleshoot it?

The only "light switch", other than the breaker is behind the unit and not accessible. I checked the breaker, it was still on...I turned it off, waited 30 seconds, turned it back on, which did not help.
 

doechsli

Well-Known Member
Joined
May 29, 2012
Messages
68
Reaction score
23
The cap is located on the outside unit. Troubleshooting is problematic unless you have the correct meter however the caps are fairly inexpensive (20-40 bucks) and not too difficult to change. That said, if you don't know your way around electricity either find a competent friend or hire a pro.

Google AC starter cap and I bet a video pops up.....

Again, I have some doubt that is your issue since the inside fan is not working.

I'd start at the thermostat.......

Someone with more knowledge than I will jump in here soon.....

edit----I see you are in south Florida and may not have the combo of furnace/AC that I am used to seeing.....so my answers are subject to being totally off base.
 
Last edited:

kok328

Well-Known Member
Joined
Nov 19, 2007
Messages
2,968
Reaction score
298
Problem is not the cap, symptoms don't lead to that.
You have to trouble shoot your way through but I'm putting my money on a blown control board fuse.
Check that first. If it is good then post pics and find your volt meter.
 

o2284200

Member
Joined
Oct 22, 2012
Messages
221
Reaction score
11
Thanks!
How do I check for a blown control board fuse?
Here are some pics:

Air handler wiring






thermostat3.jpg
 
Last edited by a moderator:

o2284200

Member
Joined
Oct 22, 2012
Messages
221
Reaction score
11
I found one large purple fuse, inside air handler, which looks OK
FWIW... I have one of those cheap 7 function digital multimeter from HF as well as a Milwaukee pen style digital multimeter.

 

overkill

Member
Joined
May 30, 2013
Messages
6
Reaction score
0
First ,check and see if its a bad thermostat,by bypassing it.
Take the thermostat cover off, then take the red,and yellow wire and connect the two. no need to turn the power off,its only 24volts and will not harm you.. did the system start ? if yes, then replace your Tstat. If not,then connect the wires back as they were,then procede with the following.

3 things you can do yourself , and for your situation, I would turn off your power to the outside unit. Open the panel and look at the capacitor. Is it swollen on top ? if yes,its a bad cap. ,if not swollen, I would take a multimeter and check voltage to the contactor, on the terminals L1 and L2 ( that's the power coming from the outside units power panel) from the house . Check L1 L2 and make sure you have 240 V. ,next you could take an insulated screwdriver and wear heavy rubber gloves,and press down on the contacts for a second and see if it all starts up.. If it does then its a bad coil not pulling the contacts down on its own.. Be carefull around the electrical part,get someone to do this if your not comfortable.. A capacitor and a contactor both cost about $25-35.. you'll save a ton if you can do this
 
Last edited:

overkill

Member
Joined
May 30, 2013
Messages
6
Reaction score
0
Here is my capacitor I just changed last week. The new one is on the left, and bad one on the right.. You see how the top is swollen ? That's a sure sign you can look for... If you find it bad. Note,your wiring.. Brown = Fan .. Yellow = C (common) and Blue = Herm (that's the compressor) ..
Power off on the outside unit, drain the capacitor by touching a screwdriver across the terminals on the cap . They can hold enough power to shock you even when disconnected,so play it safe and drain the cap before handling..

goodbad capacitor.jpg
 
Last edited:

kok328

Well-Known Member
Joined
Nov 19, 2007
Messages
2,968
Reaction score
298
Fuse is good.
Start with line power to the unit.
Check the control board for flashing light code & reference code the legend on back of cover panel.
Check for 24volts on the secondary side of the transformer.
Check for 24vokts at the tstat.
Post back findings.
 

o2284200

Member
Joined
Oct 22, 2012
Messages
221
Reaction score
11
Fuse is good.
Start with line power to the unit.
Check the control board for flashing light code & reference code the legend on back of cover panel.
Check for 24volts on the secondary side of the transformer.
Check for 24vokts at the tstat.
Post back findings.
Forgive my ignorance but how do I do these, exactly?
 

kok328

Well-Known Member
Joined
Nov 19, 2007
Messages
2,968
Reaction score
298
If not comfortable using a DMM or don't know how to check for voltage then probably better to call a tech.
 

kok328

Well-Known Member
Joined
Nov 19, 2007
Messages
2,968
Reaction score
298
Ok you can't check power at the tstat cause you don't have a common wire "C" terminal.
Start with Line power.
Open the cabinet and find where power comes in from the service switch.
Check for power between the unit and the switch.
If you have power there then move onto the transformer.
Post a clear pic of internals if you need help on that part.
Any flashing LED light on any control boards?
 

o2284200

Member
Joined
Oct 22, 2012
Messages
221
Reaction score
11
Ok you can't check power at the tstat cause you don't have a common wire "C" terminal.
Start with Line power.
Open the cabinet and find where power comes in from the service switch.
Check for power between the unit and the switch.
If you have power there then move onto the transformer.
Post a clear pic of internals if you need help on that part.
Any flashing LED light on any control boards?
I have not noticed any flashing LED light on any control boards but I do have the service switch turned off. I believe the power comes in from the service switch with the 2 black & 1 green wires on the top right, which lead to a breaker in the top center. If correct, how do I use my multi meter to check for power between the unit and the switch?





 

Latest posts

Top