Air Conditioning - A/H not Running
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tix6174
07-29-06, 12:44 PM
Hi All!
Found this site while trying to solve my A/C problems and has been a tremendous help!!!
I have a 10 year old dual-zone split heat pump system (I think that's how to put it). One unit for the down-stairs and another larger system for upstairs. This Lennox system was installed when the house was built. 3.5 tons for the down and 4 ton up. The Air Handler/Furnace is in the attic and the compressors outside on the pads.
I have replaced the compressor fan in one unit and the caps (dual run) in both units and has worked great for about 2 months. Now the upstairs zone A/H will not always come on but the compressor (and fan) does and will stay on until if ices up if I let it. The contactor engergizes and pulls in. If I "play" with the heat/cool setting of the thermostat sometimes the blower comes on and sometimes it doesn't. Other times it works just fine without touching it.
I have checked the t-stat voltages and only see 24V on R to C. Never on R to G or R to Y1. I have 24v on the same R and C at the contactor, but only see 2-5V on the contator terminals.
Is this a t-stat problem? Or a contactor? Or something else?
Found this site while trying to solve my A/C problems and has been a tremendous help!!!
I have a 10 year old dual-zone split heat pump system (I think that's how to put it). One unit for the down-stairs and another larger system for upstairs. This Lennox system was installed when the house was built. 3.5 tons for the down and 4 ton up. The Air Handler/Furnace is in the attic and the compressors outside on the pads.
I have replaced the compressor fan in one unit and the caps (dual run) in both units and has worked great for about 2 months. Now the upstairs zone A/H will not always come on but the compressor (and fan) does and will stay on until if ices up if I let it. The contactor engergizes and pulls in. If I "play" with the heat/cool setting of the thermostat sometimes the blower comes on and sometimes it doesn't. Other times it works just fine without touching it.
I have checked the t-stat voltages and only see 24V on R to C. Never on R to G or R to Y1. I have 24v on the same R and C at the contactor, but only see 2-5V on the contator terminals.
Is this a t-stat problem? Or a contactor? Or something else?
Ed Imeduc
07-29-06, 02:12 PM
Now the upstairs zone A/H will not always come on but the compressor (and fan) does and will stay on until if ices up if I let it. The contactor engergizes and pulls in.
Not sure what unit you have there. I take it its the blower fan in side that dont work.Dont let the unit run outside till this is fixed.
Will the fan come on at the stat fan on??
Or jump R to G at the stat fan should come on .If not can be fan relay on in the board there.
Also when it calls for just fan help push the blower wheel and see if it starts if so get a new capacitor for the motor. if not and you have 220V there for the motor then its a new blower motor. LOTS AND LOTS OF IFS IFS .
ED;)
Not sure what unit you have there. I take it its the blower fan in side that dont work.Dont let the unit run outside till this is fixed.
Will the fan come on at the stat fan on??
Or jump R to G at the stat fan should come on .If not can be fan relay on in the board there.
Also when it calls for just fan help push the blower wheel and see if it starts if so get a new capacitor for the motor. if not and you have 220V there for the motor then its a new blower motor. LOTS AND LOTS OF IFS IFS .
ED;)
tix6174
07-29-06, 10:34 PM
Thanks for the reply!
Yes the blower I'm referring to is in the air handler in the attic. The compressor will come on every time the t-stat commands but the blower will not always. Some times it will and some times not.
I went up there today (don't envy you guys for that!) and when the t-stat is set to on or auto, you can hear a small relay click but nothing from the blower motor. When I try to jumper R to G at the t-stat, it does the same.
I'm thinking it might be a relay on the furnace control board now. Maybe? Putting too much thought into this?
I'm not letting it run except when I can watch and make sure the compressor isn't running by itself. :D
Where is the blower motor cap on the a/h (furnace)? It's a Lennox 84MG I think. I double check in the am.
Yes the blower I'm referring to is in the air handler in the attic. The compressor will come on every time the t-stat commands but the blower will not always. Some times it will and some times not.
I went up there today (don't envy you guys for that!) and when the t-stat is set to on or auto, you can hear a small relay click but nothing from the blower motor. When I try to jumper R to G at the t-stat, it does the same.
I'm thinking it might be a relay on the furnace control board now. Maybe? Putting too much thought into this?
I'm not letting it run except when I can watch and make sure the compressor isn't running by itself. :D
Where is the blower motor cap on the a/h (furnace)? It's a Lennox 84MG I think. I double check in the am.
Ed Imeduc
07-30-06, 09:34 AM
The blower is right there in that unit there in the attic. Now with the door off call for fan on and give the blower wheel a push if it starts its just the capacitor. If not its a new blower motor and new capacitor LOOK OUT WHEN YOU TRY THIS.
Sounds like the stat and relay are ok
ED;)
Sounds like the stat and relay are ok
ED;)
tix6174
08-02-06, 10:49 PM
Ok - been checking out things a little more and I've determined it must be in the control board of the furnace (Lennox 80MGF).
When I went to check the blower as suggested, I pulled off the cover and when I had the wife flip the t-stat over I hear a small click from the board but the blower doesn't come on. I put a finger on the relays trying to see which one it is and as soon as I touch anything connected to the board (wires, relay, board itself) the blower will come right on and run for about 2 days without a single problem!
I've tried to see if it is just the heating or cooling side, but both act the same. Looking around with Google, it seems this particular series of furnace has a long history of control board problems. A new board seems to run about $250. Any idea what this "upgraded" board has that makes it so much 'better'.
I could swap it myself, but it seems to be just a loose connection somewhere. Any ideas on where?
One site mentioned just replacing the relays for about $10! I've found them at Mouser so I may try that. Oh and the second unit has just started to act the same way.
I'll keep checking to try and determine where the problem is and keep this thread updated so if anyone else has the same problem it could help them.
When I went to check the blower as suggested, I pulled off the cover and when I had the wife flip the t-stat over I hear a small click from the board but the blower doesn't come on. I put a finger on the relays trying to see which one it is and as soon as I touch anything connected to the board (wires, relay, board itself) the blower will come right on and run for about 2 days without a single problem!
I've tried to see if it is just the heating or cooling side, but both act the same. Looking around with Google, it seems this particular series of furnace has a long history of control board problems. A new board seems to run about $250. Any idea what this "upgraded" board has that makes it so much 'better'.
I could swap it myself, but it seems to be just a loose connection somewhere. Any ideas on where?
One site mentioned just replacing the relays for about $10! I've found them at Mouser so I may try that. Oh and the second unit has just started to act the same way.
I'll keep checking to try and determine where the problem is and keep this thread updated so if anyone else has the same problem it could help them.