Heater and AC running at the same time

Reply

  #1  
Old 09-05-13, 04:14 PM
Member
Thread Starter
Join Date: Mar 2013
Posts: 20
Heater and AC running at the same time

Goodman heatpump/ac unit
Goodman air handler/furnace

What could be the cause of the heat strips coming on with the AC? I've replaced the control board and sequencer in the air handler. I've replaced the thermostat. The wiring appears to be correct, but there's a chance I may be missing something simple. The problem is random. It can be fine for quite awhile, and then it suddenly does it again. After replacing the control board and sequencer the 1st time (it's been done twice now) the problem seemed to be fixed only to come back again about 2 weeks later. Then I switched out the board and sequencer, but it didn't resolve the issue. I put the last control board and sequencer in another unit, and it works without any problems.
 
Sponsored Links
  #2  
Old 09-05-13, 05:41 PM
Member
Join Date: Dec 2012
Location: United States
Posts: 239
could be a wiring fault, for example the insulation is bad/missing on the AUXiliary wire (E say) which then shorts intermittently to the compressor signal (Y)...
Have you tried disconnecting the auxiliary heat wire(s) at the handler control board ?
 
  #3  
Old 09-05-13, 06:42 PM
firedawgsatx's Avatar
Member
Join Date: Jul 2013
Location: USA
Posts: 1,727
I have seen this one other time. It turned out to be a short in the thermostat wiring due to two wires touching at points with missing insulation. Turn off power to the air handler. Remove the wires from the thermostat and do a continuity test between the wires to see if any of them are shorting to each other. Set your voltmeter to continuity and place one probe on one wire and the other probe on the other wire. If you get a "beep" (if your meter has that function) showing there is continuity between the two wires then you found your problem. Otherwise, if you get a reading of 0 then those two wires are touching somewhere. What you want to see between any two wires is an "OL" or infinity reading.
 
  #4  
Old 09-06-13, 08:12 AM
Member
Thread Starter
Join Date: Mar 2013
Posts: 20
I'll try the continuity test, thanks for the info.

I have tried to disconnect the white/brown wires where they tie in with the wires going outside and to the sequencer. I also disconnected the yellow wires where they connect heading outside from the air handler. I'm actually pretty ignorant about the wire color coding and the purposes of each.
 
  #5  
Old 09-06-13, 08:35 AM
firedawgsatx's Avatar
Member
Join Date: Jul 2013
Location: USA
Posts: 1,727
The common color codes for wiring are:

Red-sends 24VAC power to the thermostat. This wire comes from the low voltage side of the transformer.
Blue-constant 24VAC to power the thermostat so batteries are not necessary. This wire comes from the low voltage side of the transformer in the air handler. This wire also goes outside to the condenser.
Yellow-for cooling to low voltage signal to contactor to activate compressor
Orange-for reversing valve at heat pump
Green-blower fan relay
White-for heat relay

Of course, not all installers use this common color code to wire systems. They might have a personal preference or just use whatever color wire they have on the van. Sometimes the wire might change color at the very end when a splice has been done.

So based on the color code I supplied that would imply there is an issue with the white wire that connects to the heat strips in the air handler. If you do the continuity test and don't find anything I would turn off the power to the air handler and remove the white wire from the control board. That should turn off the heat strips until you can isolate the problem.


Pay particular attention where wires go through knockouts in metal panels. That is where the insulation is most likely to get rubbed off and cause shorting problems. Also check the thermostat wiring terminals. If the wire insulation is cut back too far the bare wires will have more of a chance to touch. The "y" and "w" wires would be the most likely to cause the problem you are having.

Also, check each wire for a short to ground.
 

Last edited by firedawgsatx; 09-06-13 at 08:52 AM.
  #6  
Old 09-06-13, 01:34 PM
Member
Thread Starter
Join Date: Mar 2013
Posts: 20
Thanks for that info!

I disconnected all thermostat wires and checked for continuity. They were all fine from the thermostat to the air handler. I did find a fault with the white and brown going outside to the heat pump.

The white goes to white on the circuit board outside, and the brown ends up on the yellow on the same circuit board, but first goes to a blue wire with a pink stripe, which then goes to some sort of sensor (possibly a pressure safety switch).

Monday I'll use two of the unused wires in the cable to replace the ones in question.
 
  #7  
Old 09-06-13, 01:59 PM
firedawgsatx's Avatar
Member
Join Date: Jul 2013
Location: USA
Posts: 1,727
If I am not mistaken that blue wire with pink stripe should be on the "y" terminal on the defrost control board. It leaves the "y" terminal and goes to the high-pressure switch. It comes out of the high pressure switch and is wire-nutted to the yellow wire that goes inside to the air handler. The white wire goes on the "w" terminal on the defrost board and then goes to W2 on the control board in the air handler. Usually the only brown wire I see on a Goodman heat pump is the one off the fan motor to the run capacitor. Maybe they used a piece of brown wire to extend the yellow wire. If you can tell us the model number of your Goodman air handler and condenser we will be better able to help you.

The wires that usually leave the air handler and go outside on a standard Goodman heat pump are red, yellow, white, orange and blue if the installer follows a schematic.

That is great you have extra wires available. That is why I am an advocate of always running a bundle with a couple of extra wires for situations such as yours. Glad you made progress solving your issue.
 

Last edited by firedawgsatx; 09-06-13 at 03:38 PM.
  #8  
Old 09-09-13, 08:49 AM
Member
Thread Starter
Join Date: Mar 2013
Posts: 20
You're right. They used brown to connect to the yellow from the thermostat for some reason. I switched the brown over to the unused yellow, and white to the unused blue. Fired up the AC and it's cooling fine at the moment. I'll continue to keep an eye on it.
 
  #9  
Old 09-09-13, 09:15 AM
firedawgsatx's Avatar
Member
Join Date: Jul 2013
Location: USA
Posts: 1,727
Glad to hear you got it fired up. Thanks for letting us know.
 
Reply

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


Thread Tools
Search this Thread
Display Modes