T-stat is not the problem since you can turn on the fan.
Do you have fuses at the outside disconnect? Have you checked/replaced them? Have you verified that you have 220 v at the compressor? ( really
230 -240v )The fan only running when the fan switch is set to ON sounds like a bad thermostat fan switch.
The fact that the outdoor unit clicks when you are calling for cooling sounds like no power to the outdoor unit.
Rain should have nothing to do with it.
Fan relay and wiring are OK. Compressor contactor coil is OK (clicking sound).
Start changing parts and you may fix it eventually. Buy a window unit for cooling now, run the furnace blower to make it bearable in the whole house. Wait for the service tech.
Stretch
I have a 10 year old home with a Lennox HS24 central air unit. When the indoor thermostat calls for cooling (or heating) , neither the furnace or the a/c turns on. When I set the thermostat for cooling, I can hear a "click" as the unit attempts to respond but nothing happens (same situation with the furnace for heat).
I can control the fan (which does work) from the thermostat. I've reset all circuit breakers and the unit still does not run. I've checked the outdoor a/c unit for obstructions, frozen lines etc. and everything appears (to a layperson) to be OK.
I've got a call into a local HVAC repair company but, given the warm temps, not going to be able to get anyone out for three days. Any simple suggestions would be appreciated. We did have a power surge in the house due to a lightning storm that tripped a couple breakers a few weeks ago. The a/c did continue to function for several days afterwards. Would it be worth my time and trouble to replace the thermostat?
Suppose to be in the high 80s next few days and I hate to have the family suffer in the heat if the solution is one I could readily tackle.
Thanks!
appears (to a
Not really-all it means is that he can turn the fan on manually. Says nothing about the AC contactor or gas valve circuits..
To the OP, can you hear a clicking at the condenser (outside unit) when the stat calls for cooling?
Yes, I do hear a clicking noise at the outside unit when the thermostat calls for cooling.
Thanks !
Also, does the furnace blower fan come one when the stat is on auto and calls for heat or cool? .
You could jumper the red and yellow wires at the stat (R and Y terminals) just long enough to see if the outdoor unit comes on. If it does, you need a new stat.
thermostat
OK, then, check the fuses at the disconnect as the other poster suggested.. And disregard my other post about jumpering the stat terminals...
One other question-does the furnace blower motor (fan) come on when the stat calls for cooling?
No, nothing happens (other than the previously noted clicking sound) when I select either Heat or Cool.
This may be just strange coincidence but the unit wasn't working but I had left the thermostat turned to Auto and Cool. We had a fairly strong t-storm with heavy rainfall and the outside unit turned on and ran (and did cool the house). Not sure how long it ran. This happened in the evening and it wasn't functioning again in the morning when I got up.
I also ran the fan at one point and then turned the stat to Cool. The outside unit did kick in and run.
This happened 24 hours+ ago and I have not been able to duplicate the above since.
Jim
No, the fan does not come on when set to Auto (and either Heat or Cool). The fan only runs when the stat is set to Fan.
Thanks !
Sounds like a bad connection in the outdoor unit.or a compressor overload thermal switch . There should be a service disconnect outside and near the unit. Try turning the disconnect on and off a few times (if so equipped). It may not be a fused disconnect unless you have a utility interruptible system (2 meters). If there are circuit breakers in your panel, turn them off then back to on and see if that makes things work. If you do decide to check connections, make sure you throw the disconnect and lock it out!
I have to say I'm not familiar with any interlocks that may exist in a Lennox system so I'm hesitant to suggest jumpering the stat terminals to see if everything will come on. It's rather puzzling that the furnace blower motor does not come on when the stat is in auto mode.
Good luck
Thanks !
One more thing, change the batteries in the thermostat.
Definitely.
A quick follow-up: The thermostat was defective. Installed a new stat and the system now works fine.
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