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HVAC Guys - AC Unit issue - I'm shuked (1 Viewer)

Warrior

Warrior

Footballguy
I'll keep this succinct. At the beginning of winter, I was having furnace issues. The fan was blowing, but the burners weren't cutting on, so it was cold air circulating. The issue turned out to be a bad connection between a wire harness and the control board. The fix was to buy and install a new control board, which I did without much trouble. Worked perfectly and I had heat all winter.

Fast forward to today, when I turned my AC unit on for the first time this year. A similar issue - air circulating, but the AC unit won't cut on to cool the air down. The outside AC unit doesn't turn on at all. In fact, it doesn't make a peep. No sound of it trying to turn on, no sound of the air compressor trying to work, no movement by the fan, etc. Here are some things I already went through while troubleshooting (sorry if my terminology is off, I'm a rookie):

  • Ensured that the thermostat was set on Cold, and at a much lower temperature. The AC is in fact on and should be circulating cold air (but isn't)
  • Breaker to the outside AC unit is ON. Flipped it off and on again just to make sure.
  • I blew of the fan blades to ensure they could turn unencumbered. No issues there.
  • In the small box installed on the wall outside of my house, next to the AC unit, I pulled the handle that cuts power to the unit. I inspected the connections inside, nothing unusual.
  • I took the outside plate off the unit and the capacitor has no visible signs of failure (bulging).
  • Inside the unit, I see no signs of wires that are loose, burned out, chewed on by mice, etc.
  • I double checked the control panel on the furnace in the attic. Everything is connected, nothing loose or obviously out of order.
After tons of YouTube videos and online tutorials, I'm stuck. Almost every video shows what to do if the AC unit fan works but not the compressor, or vice versa. In the videos, you can hear noise coming from the unit as it tries to engage but can't. On mine, it's completely dead, like it's not getting the signal to even turn on.

Any ideas? I'm stumped!

(Thanks in advance!)

 
Wooderson said:
Have you installed a new thermostat of late ?
Click to expand...
I have not. It's the same run of the mill thermostat that I inherited from the prior owner. I did replace the batteries as a last-ditch effort today just on the off chance that it could be causing the issue. It displays "Cool" and the picture of a fan to confirm that it's trying to use the AC. 

Oddly enough, I recently started looking for a new thermostat that I can use with my Echo. Do you think it knows I was considering cheating on it? :oldunsure:

 
Last edited by a moderator:
If your condensing unit worked fine last year, then you should b fine.  I would bet it is a wiring issue.  When your thermostat calls for AC, the mother board turns on both the blower in your furnace/air handler and the condensing unit outside.  I would bet the tech either incorrectly wired the condensing unit or didn't wire it at all.

I am more familiar with the heating side of hvac, so I am kinda shooting from the hip here.  When you take off your thermostat, I would guess there are the following wires white (common), red (heat), green (fan) and yellow/blue (?) which would b your condenser.  Here is what I would do.  Since we know the heat works, we'll use that as a control, I would take a piece of wire and jump from red to white, this should turn on your heat.  Next I would jump from green to white, which I think will just turn on your blower.  Finally, jump the yellow/blue to white, this should activate your condenser outside, if it doesn't, you probably have the afore mentioned wiring issue.

 
NFL-ons said:
If your condensing unit worked fine last year, then you should b fine.  I would bet it is a wiring issue.  When your thermostat calls for AC, the mother board turns on both the blower in your furnace/air handler and the condensing unit outside.  I would bet the tech either incorrectly wired the condensing unit or didn't wire it at all.

I am more familiar with the heating side of hvac, so I am kinda shooting from the hip here.  When you take off your thermostat, I would guess there are the following wires white (common), red (heat), green (fan) and yellow/blue (?) which would b your condenser.  Here is what I would do.  Since we know the heat works, we'll use that as a control, I would take a piece of wire and jump from red to white, this should turn on your heat.  Next I would jump from green to white, which I think will just turn on your blower.  Finally, jump the yellow/blue to white, this should activate your condenser outside, if it doesn't, you probably have the afore mentioned wiring issue.
Click to expand...
So here's now the installation of the new board went (I watched): He unplugged and removed all wires from the old board, one by one, and plugged/attached each one to the new board, making sure they were securely in place. Then he un-clipped the old board from the brackets and clipped in the new one. I am sure that every wire attached to the old board was now attached to the new one (and today double checked that nothing is loose, etc.). After doing this, the furnace lit up and worked perfectly with the new board.

I'll also note that the new board has a light that flashes for corresponding error signals if anything is wrong. That light is not displaying any errors, though I'm not familiar enough with this sort of thing to know whether it would even detect an issue like this.

I agree that this issue is very likely connected to the installation of the new board, since the AC unit isn't powering up at all and hasn't been used since the board installation.

If I'm looking at the board, do you know which wire/area I should look to in order to check and see if it's connected correctly to the condensing unit? Here's a picture of the board:

http://www.emersonclimate.com/en-us/Products/Products_A_Z/Furnace_Ignition_Control_Gas_Valve_Ignitor_Thermocouple/PublishingImages/furnace_hi_res_photos/50m56-743_RT.JPG



(White Rodgers 50M56-743 Goodman OEM Direct Replacement Control)
 



Thanks so much for the help. If I could get an HVAC guy out here tomorrow, I'd have him check it out for me. Unfortunately, I won't be available to have someone come out until next Friday (9 days from now).

 
NFL-ons said:
If your condensing unit worked fine last year, then you should b fine.  I would bet it is a wiring issue.  When your thermostat calls for AC, the mother board turns on both the blower in your furnace/air handler and the condensing unit outside.  I would bet the tech either incorrectly wired the condensing unit or didn't wire it at all.

I am more familiar with the heating side of hvac, so I am kinda shooting from the hip here.  When you take off your thermostat, I would guess there are the following wires white (common), red (heat), green (fan) and yellow/blue (?) which would b your condenser.  Here is what I would do.  Since we know the heat works, we'll use that as a control, I would take a piece of wire and jump from red to white, this should turn on your heat.  Next I would jump from green to white, which I think will just turn on your blower.  Finally, jump the yellow/blue to white, this should activate your condenser outside, if it doesn't, you probably have the afore mentioned wiring issue.
Click to expand...
And regarding the wires behind the thermostat, I'm seeing White, Red, Yellow and Green attached.

Blue, Brown and Orange are each present as well, but none are connected. They are shorter than the others and wrapped around as if they were never used (not as if they simply fell out of the clips)

 
Last edited by a moderator:
He actually mentioned in the original post that he had confirmed power. 

Sorry, I have never seen AC wired only using 3 wires.

 
NFL-ons said:
He actually mentioned in the original post that he had confirmed power. 

Sorry, I have never seen AC wired only using 3 wires.
Click to expand...
Correct. And I just updated my post, I missed the red wire, which was connected in a different way than the others.

I'm seeing White, Red, Yellow and Green attached. (matches your diagram)

Blue, Brown and Orange are each present as well, but none are connected.

I was hoping I would open this thing up and see one of the wires had slipped out, but no luck!

 
Holy mother of God, you did it!!! I went up to the attic and spent about 25 minutes un-capping and checking the connections where 'C' wires were spliced together, then checked all the 'Y' wires. Then I double checked where they are screwed into the circuit board. Still nothing. Then I checked where the 'C' wire extends to the drip pan (a control to shut it off if it fills?) and checked to see if that contraption may have been preventing it from turning on. Then after all that failed, I came back and checked your diagram for a third time, went back up and studied the wiring again. All color wires were going to their respective correct homes...R...G...C...W...Y....wait! I remembered your diagram where the Y goes to the thermostat AND the condenser. Then I noticed that among the huge bundle of wires, a second yellow was unattached (didn't catch my eye because the unused extra R, G, W were hanging out with it! I plugged Yellow #2 under the screw along with Yellow #1 and danced down the stairs like a school girl, flipping the breaker and running outside to hear the whirrrrrr of my air conditioning unit!

You rock man, thanks so much! Can I buy you an Amazon gift card or something? It's the least I can do - I never would have figured it out without your help, and now I wont be miserable waiting the next 9 days for someone else to come fix it (and charge me!)

 
Can you send me a PM with your email address? I'd like to get you an Amazon GC, it's the least I can do! Thanks again

 
Any way I can piggyback in here?  I'm in the final stages of choosing a new HVAC system for our home (GA).  I'm pretty well set on a 14 SEER dual fuel HP with 80% natural gas furnace.  I looked at jumping up to 15 SEER, 95%, and/or variable speed but have decided none were worth the extra $.  I'm down to 2 quotes from reputable installers - one using Carrier comfort series and the other Trane (XR14/XR80 combo).  Any advice on helping pick between the 2 brands?  TIA

 
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