Need appliance parts? Call 877-803-7957 now or use the parts search box:

Parts Search

Isn’t it time to know what you don’t know?

Click here to check out our structured, online appliance repair training courses for rookies and experienced techs.

FAQs | Repair Videos | Academy | Newsletter | Podcast | Contact

Stay connected with us...

Samurai on Facebook - become a fan today! Sign up for our free newsletter and keep up with all things Appliantology. Subscribe to our YouTube channel for lots of appliance repair tips and help! Follow the Samurai on Twitter and get timely morsels of Appliantological Wisdom! Subscribe to our MST Radio podcast to learn secrets of the trade.
sonik

Need help with AC unit wont turn on

11 posts in this topic

After buying our house i noticed that a dog had chewed up some wires going to the outside AC unit (two wires, very thin) and when using some spare wires i had to hook them up the ac unit would click as if turning on and after flipping the huge fuse on the outside wall next to it the ac would work.  If the outside fuse is off it still clicks when the wires are touched (if AC is turned on from inside).  I soldered the wires together and now for some reason it wont turn on.  I made sure thermostat was set to cool and it was set very low to make sure it should turn it on but no go.  I checked the fuse outside and it seems to be ok, its just a huge plug in fuse.  Since there is no click im assuming whatever is sending power via those two wires is not sending a signal or whatever was clicking before is now broken?  please help im not too good with ac units

Share this post


Link to post
Share on other sites

Need appliance parts? Call 877-803-7957 now!

You have to verify wiring between AC unit and thermostat. Im assuming these are the small thermostat leads.

Turn off power.    Find out where the 2 leads connect up, or terminate in AC unit.

Remove these wires ( make a note pls ), and install small jumper wire. Turn on power. Did unit start ?? If so, problem is wiring between AC unit and thermostat, or thermostat itself.

To verify this........shut off power, and put wires back where they were. Go to thermostat, and remove cover. Jumper between 2 leads in back plate. Turn on power. If unit starts, the problem is the thermostat..............if not, then the wiring is defective between thermostat and Ac unit.            Good Luck !!

Share this post


Link to post
Share on other sites

thanks for the info.. im not the best at this stuff but i can usually figure things out. yes they are two small copper wires and i had it working fine when i just connected the wires up but as soon as i soldered the wires on it stopped working, i definately agree its from the ac unit to the thermostat on these two wires but when turning the ac unit to cold and turning thermostat down no power is going on these two wires i check it, can you pleaes be more descriptive on checking the thermostat is this on the back of the termperature control panel in my house, what am i looking for.  I apreciate your help

Share this post


Link to post
Share on other sites

Hey Sonik,

   Glad to assist. On the thermostat in the house, there is only the cooling mode...right ?? Im assuming its not a heat pump, but for cooling only. You should be able to remove the cover....it might be round, or square shape....low voltage thermostat. The cover should pry off easily enough. Then there should be a couple screws holding the thermostat onto the backplate. Remove these screws, and the thermostat should come off. Then you will see where the wires connect up.

You can either jumper the wires, or take the 2 wires off and twist them together. ).( This simulates the call for cold, and should start the system. Also  give it a couple minutes to act, in case there is a time delay in starting up . If it does not start the system, chances are the t- stat is ok, and you have a wiring problem.....which it sounds like to me. Maybe check the connections that you made soldering. Sometimes these fine wires can come apart, if the solder joint is not good, especially when taping them up. Good Luck!

Share this post


Link to post
Share on other sites

ok thanks, like i said it worked until i soldered the wires so maybe youre right as of now its like this for the wires

 

AC============================Control panel

 

the cpanel controls heat and the AC and has a Off, Heat, Cool setting so what i want to do is at the cpanel or even at the ac unit just touch the wires together?  I checked for voltage on them both and theres nothing at the ac unit

Share this post


Link to post
Share on other sites

  So your control panel has a heat function as well ? Is it also a heat pump, or just an AC unit ? I would think since it only has 2 wires , that possibly that controller may be a standard style that they used, and only the cool works??  ( Some of the newer thermostats have 2 wires for heat and cool, but use a battery for power, but I have not used any of these to date ).

Just want to make sure you are not using a " solenoid " type of meter,( it has a bar which moves in the meter, which snaps up and down when measuring voltage ) which will only trigger at about 70 volts ac / dc. Just want to make sure that we have the proper meter. Control voltage on t- stat should be 24 v   ac.

Lets start at the beginning. Shut off power. Pull fuse ( s ) and check for continuity with a multi meter on ohms. ( Touch the leads together first to see if the meter works fine...........just to be sure ) . If ok, put fuse back in, turn on power.

Let see how we make out with this, before going on.

Is there a pic of the wiring schematic  you could post ??

 

 

Share this post


Link to post
Share on other sites

sure was hot this weekend..  i took off the control panel and there are 4 wires but i can see the red wire and white wire which lead to my AC unit so these are the ones that control the ac.  I actually bought a new control panel and hooked it all up and still no go.  I almost think that one of the wires between control panel and the ac unit has been broken or something its just too weird.  I was gonna run two wires from the pins on the back of the control panel right out the window down to the AC unit to see if it would work that way but i didnt have any long enough.

Share this post


Link to post
Share on other sites

you should be getting at last 24 volts ac to them 2 small wires going to the contactor what 2 wires did you solder together?

Share this post


Link to post
Share on other sites

at all times? I measured them and theres nothing..put in a new thermostat and nothing.. whats the coil looking thing mounted on the air conditioner? i soldered the two wires from the ac unit to the wires coming from the thermostat. 

Share this post


Link to post
Share on other sites

the contactor is a small black bx with large wires going in and out of it this controled by those 2 small wres when you turn on the wall stat the two little wire power up the coil in this box called a contactor this snatches down the contacts and makes the fan and compressor come on . if you are a brave man you can take an insulated screwdriver and mash down on this contactor and see if the unit will fire up. be caredul though because its dangerous you could be electrocuted . If its a 2 pole open contactor you can usually push down on the top of it and see if the ac unit will fire off just for testing purposes but be careful you dont get shocked:yikes:

Share this post


Link to post
Share on other sites

1 - is your meter capable of measuring 24 volts ac? Dont mean to sound repetitive, but we have to ensure this.

2 - You should have 24 volts on the 2 wires, providing the thermostat is open. Once it is closed, you would have nothing since you are powering up both lines, so to speak.

3 - Like appliance man suggested, power the unit down, and see if the contactor will push in manually. It should spring back out, when you let it go. The front part of the contactor should move in, and out.

4 - Do as I suggested earlier on, and see if twisting the 2 wires ( red & white ) will start the unit. I would not start buying parts at this stage of the game. You may not be able to return them if they are not the problem. As well, finding and sourcing out the problem is a learned skill......which is what we are doing. Keep us posted.:)

 

Share this post


Link to post
Share on other sites