Service Forum for Lennox HVAC Owners and Servicers.
Enter Our Parts Store | Forum Home | Profile | Register | Active Topics | Members | Search | FAQ
Username:
Password:
Save Password
Forgot your Password?

 All Forums
 Repairing and Servicing Lennox Products
 Repairing / Servicing Lennox Air Conditioning
 Lennox ac wont turn on with thermostat
 New Topic  Reply to Topic
 Printer Friendly
Author Previous Topic Topic Next Topic  

Dave73

4 Posts

Posted - 03/27/2011 :  3:45:44 PM  Show Profile  Reply with Quote
System:
2 story home
Both furnace/ evap units above second floor
Lennox 13ACC-030-230-02 outside unit
G4OUH(X) furnace
CH33-36A-2F evap
Honeywell Whole House Ventalation Control for upstairs unit (I am clueless on this)

Both units are identical except for the Honeywell vent control

I have what seems to be an unusal problem with the upstairs ac unit. Heat works fine. The thermostat will not turn the system on at the appropriate temperature. I have installed three different thermostats, and have swapped the thermostat from the other unit to test. The problem is not the thermostat. I have tested and the thermostat is switch on.

I can jumper the RB to the Y (red to yellow) connection at the thermostat connector and the unit will work. I do get a significant little arc/ spark when installing the jumper wire. It seems to me that *something* is drawing more current than the thermostat can handle.

I know the Honeywell unit is tied into the yellow wire as well, but as I said I am unsure what this thing is supposed to do. I cant find a model number on it and I didnt get much from a little searching. It has a three position switch, and changing the setting makes no difference in the lack of ac operation. It appears this unit is wired in between the thermostat and the furnace circuit board.

I started having this problem late last year, and just got by until winter. Now its time to get it working correctly. I also swapped the circuit boards while testing, and that made no change.

Any tips would be very much appreciated. Since I have two identical units, I have no issue with swapping parts to test, but I am unsure where to go from here.

Cozy.Support

5779 Posts

Posted - 03/27/2011 :  4:47:57 PM  Show Profile  Reply with Quote
Are you having issues n the cooling mode?



CozyParts.com, Inc. is an Independent Lennox Dealer providing a national parts distribution resource for Lennox parts since 2002. The Cozy.Support team does not provide a diagnosis for users of this forum. We do, however, try to provide information that will help servicers arrive at their own diagnosis.

Once you know what part you need, you can contact the Cozy parts department by using the link below
http://www.cozyparts.com/Lennox-Parts/locator_form.aspx
Go to Top of Page

Dave73

4 Posts

Posted - 03/29/2011 :  6:46:41 PM  Show Profile  Reply with Quote
Yes. The thermostat will turn on the inside fan and furnace fine. When in ac mode it will not turn on at the designated temp. If I install a jumper wire in place of the thermostat the ac turns on, fan turns on, and system cools great.

I have tried three different thermostats, and even swapped the known good thermostat from the downstairs unit to the upstairs (inop) unit.

It seems as if something on the Yellow 'cooling' circuit is pulling too much current (spark seen when installing jumper)
Go to Top of Page

Dave73

4 Posts

Posted - 03/29/2011 :  7:10:17 PM  Show Profile  Reply with Quote
Also, I have verified the thermostat and associated wiring is routed correctly.
Go to Top of Page

Cozy.Support

5779 Posts

Posted - 03/31/2011 :  10:27:06 AM  Show Profile  Reply with Quote
So while in the cooling mode, the thermostat will turn on the blower at the correct temperature, but it does not always turn on the air conditioning at the same time it turns the blower on?



CozyParts.com, Inc. is an Independent Lennox Dealer providing a national parts distribution resource for Lennox parts since 2002. The Cozy.Support team does not provide a diagnosis for users of this forum. We do, however, try to provide information that will help servicers arrive at their own diagnosis.

Once you know what part you need, you can contact the Cozy parts department by using the link below
http://www.cozyparts.com/Lennox-Parts/locator_form.aspx
Go to Top of Page

Dave73

4 Posts

Posted - 04/03/2011 :  9:17:56 PM  Show Profile  Reply with Quote
In cooling mode, the thermostat will not turn on the blower or outside unit. I have tested the thermostat with an ohm meter and with the known good unit downstairs. The thermostat is good and working normally, it just wont turn anything on because of a problem with one of the components on the cooling circuit.

If I install a jumper wire in place of the thermostat across the red and yellow cooling(power to Y) pins, the blower turns on and the outside unit turns on. I do get a spark when installing or removing the jumper wire.

I know thermostats are made with simple circuity and transistors that cannot support much current. I believe something on the yellow (cooling) circuit is drawing too much current, but I am unsure what, where or why.

I am unsure what the yellow cooling wire goes to, or how the outside unit is switched on. I think this may be the problem, but I am unsure about how this part of a home ac system works.
Go to Top of Page

Cozy.Support

5779 Posts

Posted - 04/04/2011 :  2:53:13 PM  Show Profile  Reply with Quote
The bottom line is that if everything can be operated from the low voltage terminal strip on the furnace, there is an issue in the thermostat or thermostat wiring. Dont rule out a back thermostat wire. Thermostat wires do go bad from time to time. Don't forget that for this model to turn on the correct cooling speed, the Y and the G terminal have to be energized at the same time.



CozyParts.com, Inc. is an Independent Lennox Dealer providing a national parts distribution resource for Lennox parts since 2002. The Cozy.Support team does not provide a diagnosis for users of this forum. We do, however, try to provide information that will help servicers arrive at their own diagnosis.

Once you know what part you need, you can contact the Cozy parts department by using the link below
http://www.cozyparts.com/Lennox-Parts/locator_form.aspx
Go to Top of Page
  Previous Topic Topic Next Topic  
 New Topic  Reply to Topic
 Printer Friendly
Jump To:
Service Forum for Lennox HVAC Owners and Servicers. © 2002-2013 CozyParts.com, Inc Go To Top Of Page
This page was generated in 0.08 seconds. Snitz Forums 2000