Go Back  DoItYourself.com Community Forums > Heating, Cooling, Air Conditioning, Ventilation and T-Stat Controls > Air Conditioning and Cooling Systems
Reload this Page >

Outdoor unit + circ fan run with no thermostat attached (cooling split system)

Outdoor unit + circ fan run with no thermostat attached (cooling split system)


  #1  
Old 06-11-20, 12:49 PM
T
Member
Thread Starter
Join Date: Jan 2004
Location: Harrisburg, PA
Posts: 565
Upvotes: 0
Received 1 Upvote on 1 Post
Outdoor unit + circ fan run with no thermostat attached (cooling split system)

I have a Goodman split cooling system with ARUF182416BA air handler where it will not turn off except with breakers.

(1) When I remove the thermostat, it still runs full time;
(2) All vents and filters are clean;
(3) The indoor coil has not dirt or ice;
(4) The outdoor unit has no dirt or ice;
(5) The circ. fan runs AND the outdoor compressor and fan run with no thermostat connected.
(6) A second and maybe just coincidental problem is that it's only cooling 3 degrees: at 90 degrees outside, the intake temp is 71 and output temp is 68 ...it cannot get below 71.

I first thought it would be a frozen contactor on the outdoor unit, but the circulation fan also runs full time.

I know a little bit about split systems, but not enough to know if I am missing something. I suppose the computer board could have gone bad? Thank you in advance!
 
  #2  
Old 06-11-20, 04:45 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Jersey
Posts: 71,641
Received 3,324 Upvotes on 2,985 Posts
Thread moved to gas and oil heating systems. You have a gas furnace with a split A/C.

The circ. fan runs AND the outdoor compressor and fan run with no thermostat connected.
Are you 100% sure ?
It's very rarely the blower AND the outside unit will not shut off....... especially with the thermostat disconnected. You didn't mention what thermostat you are using. Some have the switching parts in the base and can remain running with the thermostat removed from the base.
 
  #3  
Old 06-11-20, 05:04 PM
T
Member
Thread Starter
Join Date: Jan 2004
Location: Harrisburg, PA
Posts: 565
Upvotes: 0
Received 1 Upvote on 1 Post
Thanks for your reply PJ. I have a Honeywell which is non-programmable but digital. I removed the base as well to make absolutely sure the wires were OK and then that they were seated after re-attaching. So it did run with NOTHING (no base) connected to the wires.

But I am second guessing myself right now as I didn't run out and check the compressor/condenser when I saw that the circ. fan was running with no t-stat attached.

What would cause the blower to run with nothing connected to the t-stat wires?

FYI, this is not a gas unit. This is a Central Air only split system with electric heat kit installed.
 
  #4  
Old 06-11-20, 05:22 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Jersey
Posts: 71,641
Received 3,324 Upvotes on 2,985 Posts
My mistake. Moved back to proper forum.

There have been a lot of threads recently on this same air handler. You'll need to go into the air handler where the power wiring connects and try removing the purple wire from the EBTDR fan delay board. Turn off all the power to the air handler first and then remove the purple wire. Then power up the unit. If the blower is now off..... the sequencer has a problem.

ARUF manual (pdf)
 
  #5  
Old 06-12-20, 02:18 PM
T
Member
Thread Starter
Join Date: Jan 2004
Location: Harrisburg, PA
Posts: 565
Upvotes: 0
Received 1 Upvote on 1 Post
Thank you! I'll try that and report back.
 
  #6  
Old 06-16-20, 09:36 AM
T
Member
Thread Starter
Join Date: Jan 2004
Location: Harrisburg, PA
Posts: 565
Upvotes: 0
Received 1 Upvote on 1 Post
OK, I pulled the purple wire from the board and the fan kept running. BUT the purple wire was charred at the end and the black box (fan relay?) it's connected to is melted and deformed. So at the least I have to order a new board.

I know this will fix my fan-on-full-time problem, but is it possible it can also fix the other problem I have where the system is only cooling 2-3 degrees (not the usual 20 split temps)? It did the same thing on a 90 degree day, but today it's still only 2 degree difference on a 75 degree day.

I ask because I have a call in for a service tech and I'd love to cancel it if this will fix the poor cooling
 
  #7  
Old 06-16-20, 10:31 AM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Jersey
Posts: 71,641
Received 3,324 Upvotes on 2,985 Posts
The relay may have melted on the board. When you replace it.... make sure the three fan wires are tight. A loose connection is what causes the terminals to burn,

Check the larger copper line out at the condenser. It should be ice cold. The smaller one should be warm. Typically a reduced cooling problem is cause by either lack of airflow or low on charge.
 
  #8  
Old 06-17-20, 02:41 PM
T
Member
Thread Starter
Join Date: Jan 2004
Location: Harrisburg, PA
Posts: 565
Upvotes: 0
Received 1 Upvote on 1 Post
OK, I installed the replacement board with fan relay and it corrected the fan-always-on problem.

But to my surprise, I got cooling back! The temp splits were a 20 degree difference! ...not 2-3 I was normally getting. It's 78 degrees out right now, but I did get 2-3 degree split temps with 78 degrees the other day, so it has changed with the same outdoor temps.

I am happy that it is fixed, but I didn't know the small fan board could affect cooling, because I thought the compressor/condenser was an on/off type of thing, not controllable by a computer. There's plenty of air circulation the whole time.

For future searches, I got the Climatek B13707-35 which is a discounted replacement board for the OEM.

Thank you PJmax for all the great, valuable, money-saving advice!!!!!!!!!!!!!!!!!!!



 
  #9  
Old 06-17-20, 08:23 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Jersey
Posts: 71,641
Received 3,324 Upvotes on 2,985 Posts
Ahhhh..... a little aux heat there. Good job on the repair.
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: