AC not working


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Old 05-22-14, 05:02 PM
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AC not working

Some of you will note that I recently posted concerning a Heat Pump. The Heat Pump is for my basement only. This post concerns my AC for the 1st and 2nd levels of my home.

I have a thermostat that controls both the AC for the 1st and 2nd levels of my home, and also a baseboard radiator on the 2nd floor. Everything was working fine until I temporarily disconnected the thermostat wires going to the baseboard radiator so I could remove the radiator from the wall and repair the drywall. Before doing that, I disconnected the power to the baseboard radiator but not did not think to disconnect the power to the AC. After I disconnected the thermostat wires, one of the thermostat wires shorted against the radiator (there was a small spark). After I finished my drywall repair and reconnected the thermostat wires, the baseboard radiator works but the AC does not.

I figured I blew another 5AMP fuse in the AC air handler (as I did with my Heat Pump). But when I opened it up, I discovered no control panel and no fuse. All the wires are connected with wire nuts. I also checked the compressor unit outside and all the connections there are also done with wire nuts.

Any ideas on what is wrong or on how I should troubleshoot would be greatly appreciated. (The main circuit breakers have been checked.)

Thanks.
 
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Old 05-22-14, 06:19 PM
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Are you saying there is no defrost board in the heat pump?
 
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Old 05-22-14, 06:36 PM
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Post the make and model of the air handler.

You may have blown the 24vac transformer out.
 
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Old 05-22-14, 08:20 PM
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The air Handler is a Carrier FX4DNF037

I checked the thermostat wiring. The cooling wire has connections to the G, Y, and R; and the heating has connections to the W and RC. However, the R and RC are jumped.

In consulting my thermostat manual (Honeywell RTH6300B), it says the R and RC should be reversed and not jumped. But as I said before, it all worked before my disconnecting the baseboard heater. Moreover, I have reversed the R and RC connections and disconnected the jumper, and my problem persists.

Can I manually jump two connections on the thermostat to simulate a call for cooling to rule out the possibility that the thermostat has been compromised?

Thanks.
 
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Old 05-23-14, 05:22 AM
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Note that this is my second post since PJMAX's last reply.

I found the air handler manual online here

http://www.americancoolingandheating.../fx4d-01pd.pdf

It says a standard feature is a "Simple, 5--amp blade fuse (and a spare) to protect 40 VA transformer"

So I looked inside again and found what I think is a 3 amp blade fuse (and no spare). Pic is below. It appears I should pull the purple part from the orange part (the socket). I pulled and it doesn't want to come easy. Should I pull harder? Also, should I be concerned that this is 3 amp rather than 5 amp as the manual says it should be?
 
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Old 05-23-14, 06:31 AM
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The purple device appears to be a fuse. The amperage rating is likely stamped on the top of the fuse. It's the type that most recent cars use, so you should be able to purchase a replacement at any auto parts store. The fuse should pull out of the spade terminals (orange/red spade terminals).

If you have a multimeter, you should be able to check the fuse once you've removed it from the spade terminals. Alternatively, you can check it by checking the voltage across the fuse with the power turned on and the thermostat calling for cooling. If the fuse is good, you should read 0VAC across the fuse. If the fuse is blown, you'll likely read 24VAC.

Once you've verified that the fuse is good (or you replace it), if you're still having problems and want to remove the thermostat from the circuit, jumper the R, Y, and G terminals together. R is the 24VAC coming to the thermostat from the transformer, Y enables the compressor/condenser (outside) unit, and G enables the air handler (blower) inside the home.
 
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Old 05-23-14, 05:18 PM
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If you look at the purple device that looks like a fuse in the picture you'll notice it's black.
Keep using the ATC-3A fuse as it will offer you more protection than the 5A fuse will.

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Old 05-23-14, 08:19 PM
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Thanks to all (skagsje, bob14525, and PJMax) for your help. I replaced the 3A fuse with another one and all is well.
 
 

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