A/C contactor not firing


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Old 04-25-14, 07:13 PM
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A/C contactor not firing

I have a Goodman GSC130361A air conditioner and a Goodman GMS80903BNA furnace unit.
This year, when I first turned on the air conditioner, it wouldn't work.
I did some troubleshooting, and determined the contactor relay wasn't firing. I pushed the contactor closed with my hand, and the unit came on as it should have. I thought the firing mechanism (solenoid) had probably gone out and replaced it with a new contactor.
When I replaced the contactor, the thing still wouldn't fire, so I investigated further.
With the signal wires unplugged, I'm getting 24V ac at the control board at the blower. With the signal wires plugged into that board, but unplugged from the contactor, I'm getting 24V ac at the wires inside the air conditioner.
BUT, with the wires plugged into the contactor, I'm getting 0V ac and the contactor doesn't make the connection. Which seems very strange to me...
If anyone could help me figure out what could be going wrong, I'd be very grateful. (I'm a prideful engineer who REALLY doesn't want to pay someone hundreds of dollars to come out and replace a $15 part).

Thanks,

Steeeeeve
 
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Old 04-25-14, 08:04 PM
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Are you measuring Y to C or interrupting one leg and measuring Y to Y?
 

Last edited by Houston204; 04-25-14 at 09:01 PM.
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Old 04-26-14, 07:59 AM
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You're not getting 24-volts to the contactor coil.
Leave the terminals on the coil & check them for 24-volts.

You should be able to troubleshoot to locate the problem.
 
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Old 04-26-14, 10:05 AM
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On the control board I'm measuring from TWIN to C (the two wires that run out to my air conditioner contactor) and getting 24V if the contactor coil is not hooked up and 0V if it's wired in. Y is currently running to my thermostat, although I'm not 100% sure that's how it's supposed to be.
Outside I'm measuring 24V if the wires aren't hooked up, but when I hook them up to the coil and then measure them, I get 0V.
 
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Old 04-26-14, 10:32 AM
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Yes...... Y runs to your thermostat and then to the A/C contactor. The Y terminal on your furnace is just a splice point. You should have two wires on the Y terminal.

There should be two wires from your A/C compressor. One connects to the Y terminal and the other one connects to C on the furnace.
 
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Old 04-26-14, 10:42 AM
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So is the "TWIN" terminal just a twin of the "Y" terminal, then? Or should I move the wire from "TWIN" to "Y"? I don't think those wires have moved since last summer when the unit was working....
 
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Old 04-26-14, 10:54 AM
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TWIN is a terminal used for running two (twin) furnaces. Move the wire to Y.
 
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Old 04-26-14, 10:55 AM
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The Twin terminal is used to connect 2 furnaces together and should not be used as the Y terminal.
 
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Old 04-26-14, 11:52 AM
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So if either of you guys are ever near Indianapolis and in need of someone to buy you a beer or three, just give me a heads-up.
 
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Old 04-26-14, 11:58 AM
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So................. is everything working now.
 
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Old 04-26-14, 11:59 AM
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Sure is. Many, many thanks!
 
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Old 04-26-14, 12:51 PM
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Jeez...need A/C already? I'm in AZ and I had to go back on my furnace today (been off for almost 2 weeks). We may even see snow flurries!
 
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Old 04-27-14, 12:49 AM
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Sounds like wiring is incorrect. You are on 1 side of the coil. Plug 1 wire to right side other on left of contactor and I bet you get 24 volts. Be careful not to touch or short because this could short out your transformer. Turn inside and outside power off. Rewire leads restore power. You can just pull the 1 wire hot but just to be sure. I a lot of times pull wire with bare fingers and touch spade terminal to coil points. Coil will pull in when you get 24 volts across it.
 
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Old 04-27-14, 01:24 AM
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The OP's problem was with the Y connection at the furnace. He has already stated that his A/C is now working normally.
 
 

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