No power getting to thermostat


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Old 05-18-14, 11:51 AM
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No power getting to thermostat

The thermostat to my heat pump is getting no power. All that has changed since the last time it worked is that I disconnected a 2nd temporary thermostat wire connection at the air handler several weeks ago, and possibly the float switch became disconnected. (The heat pump has not been used for a couple of months.) I’ve made sure all the wire connections are secure at the air handler and the thermostat. (Also, I'm sure that I did not mistakenly remove the wrong thermostat wires.) I recently noticed that the float switch was not connected, but I think it most likely that that has always been the case. (My heat contractor disappeared before my project was finished.)

I attach a photo of my float switch device, a close-up of the braided wires for it, and the air handler wiring.

Any help would be greatly appreciated.
 
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Old 05-18-14, 12:29 PM
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Can you post a close up of the control board?
 
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Old 05-18-14, 12:34 PM
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Posting the model number of the air handler would be helpful too.

Did you check the 5A fuse at the top of the board ?
 
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Old 05-18-14, 01:07 PM
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Thanks for the quick replies. The air handler is a Carrier model FV4CNF002. This is shown in 1 of the photos below. The other photo shows the control panel. I'm guessing the 5A fuse is the amber colored unit. How would I check it?

Thanks.
 
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Old 05-18-14, 01:17 PM
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Pull it out and look at it or use an ohmmeter to check for continuity.
 
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Old 05-18-14, 01:47 PM
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The problem is the fuse---it is blown. Do you agree that the link below is the correct replacement?

Robot Check

Any ideas on what might of caused the fuse to blow?

Also, any guidance on how to connect the float switch would be appreciated.

Thanks.
 
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Old 05-18-14, 08:20 PM
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That is the correct fuse.... ATC-5. You can get them in auto parts stores, Radio Shack, etc.

The fuse blew because the thermostat wiring probably shorted. When changing any thermostat wiring turn off the service switch to the air handler.

At your control board.... look for the Y terminal. There should be two wires on it. One goes to the thermostat and one heads out to the compressor unit. Connect one of the float wires to the Y terminal and connect the other float wire to the yellow wire going out to the compressor.

When the float activates it will shut off the compressor unit.
 
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Old 05-19-14, 07:43 AM
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Thanks so much for your help. I have been disengaging the main fuse to the Air Handler when doing any wiring (I don't think there is a switch), but I may have forgotten to do that one time.

Regarding the float switch, the Y1 terminal on the Air Handler now has one wire coming from the thermostat and one wire coming from the compressor. I think I undersand your instructions, but just to be sure: Are you saying to disconnect the yellow wire that goes to the compressor and connect it to one of the float switch wires, and connect the other float swith wire to the Y1 terminal? And I take it the two wires coming from the float switch are interchangeable.

Thanks again.
 
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Old 05-19-14, 11:54 PM
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You do have it correct
 
 

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