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Heating & Air Conditioning

AC not turning on. Period.

9 years ago

AC will not start. Period.

Furnace - Lennox G43uf
A/C - Lennox merit 13acx
Thermostat - Honeywell rth230bÃ¯Â¿Â½

Hey guys, new to the forum. Went to turn on my AC yesterday and no dice. Won't turn on at all. Started with the thermostat first, ensured it was on cool, the temp set was lower than ambient temp and I replaced the batteries. The 30 amp double breaker is not tripped, and the secondary disconnect by the AC does not have a fuse and is on.Ã¯Â¿Â½

I have a 4 wire thermostat with a jumper. I crossed the wires from Y to Rc and G to Rc. Both only turn on the inside circulating fan. There is no sound at the AC at all. Neither the fan nor the compressor turn on.Ã¯Â¿Â½I checked the furnace, panels are all secure and the 3 amp fuse is intact. Also when the cooling sequence is activated at the thermostat the furnace reports normal cooling function led.Ã¯Â¿Â½

I've checked around the AC and I can find no visual damage and covers are secure, the furnace is approximately 5-6 years old. And I've gone through the entire manual for the AC. My question is, is there a low pressure switch on my AC that would cause it to not operate at all in the event there is a leak?Ã¯Â¿Â½I will check for continuity and 24volts on the low voltage wires going to the AC and check for any internal visual damage when I arrive home today. Based on what I've tried I'm leaning towards contactor damage? I'm hoping there's something small I've overlooked. Thanks a lot!

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Comments (4)

tigerdunes
9 years ago
Could be a bad capacitor. I don't recommend checking this unless you have basic electric experience and will take the necessary safety precautions. Use the disconnect at condenser to remove any safety issue. Usually one can make a visual of the capacitor to determine a problem. Beyond that, there are too many other possibilities.

Sorry for your trouble.

Good Luck...
Jeffromeo
Original Author
9 years ago
Thanks for the reply. I'm a second year electrical apprentice (no longer in the trade). But I have little to no experience with Hvac components. I know how to use a multimeter. I'll be checking electrical problems when I get home and will most certainly take precautions.
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Jeffromeo
Original Author
9 years ago
Double post

This post was edited by Jeffromeo on Mon, May 12, 14 at 13:12
Jeffromeo
Original Author
9 years ago
So I opened the electrical panel on the AC and verified that I was indeed getting 240v and 24v. The capacitor looks fine, but a wire leading to the contactor was brittle and making poor contact. I then opened the main compartment and found that my fan motor was completely seized. Also the low pressure switch was tripped.

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