A/C nor blower fan will start

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Old 07-03-15, 06:29 PM
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A/C nor blower fan will start

I recently turned off my a/c at the thermostat. It was running fine, so fine that I turned it off, even. About three hours later I flipped the switch on the programmable thermostat back to "cool". I heard the familiar "click"as if the thermostat was sending the signal to the a/c unit to start but nothing happened. When I turn the fan to the on position, from automatic, it will not start either. I have replaced batteries in the thermostat, changed the mode from programmable to manual, checked the breakers in the electrical service panel, and inspected the disconnect out at the unit. Any help would be MUCH appreciated!
Steve
Danville, VA
 
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Old 07-04-15, 05:10 AM
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Is the door tight on the furnace,is there a switch on the furnace that may have been shut off, do you have a volt meter and know how to use it?
Geo
 
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Old 07-04-15, 05:36 AM
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Steve, in addition to the information that Geo gave you, any additional information you can give us regarding your system will be helpful. For example, the following information would be helpful:

When thermostat calls for cooling, does outside unit (compressor/condenser fan) come on?
Is your system a furnace with A/C, or a heatpump?
If a furnace with A/C, if you set thermostat to call for heating, does inside blower come on?
Approximately how old is system, and what make/model?
Is blower a variable speed unit or just single speed?
 
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Old 07-05-15, 03:42 AM
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Use your meter to check power to the air handler .

God bless
Wyr
 
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Old 07-05-15, 11:01 AM
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I do have a volt meter. This is a separate a/c and furnace, not heat pump. I switched the thermostat to heat and still no inside blower. When on cool the condenser fan goes not come on either. The panel is on securely, safety switch is working as when I press it in manually there is a small green light that comes on in the air handler circuit board.
It is a Kenmore a/c model# 36LC-000087CR
Furnace Rheem RGRA-07EMAES
I'm unsure of the age of these
 
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Old 07-05-15, 12:22 PM
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The first thing I would suggest you check is to see if you have 24VAC from the transformer present at the thermostat. Set your voltmeter to AC volts and leave the thermostat OFF (not calling for either cooling or heating). Check the voltage between the R and Y terminals on the thermostat. You should have ~24VAC. If you have 0 volts, you may have a blown fuse for your transformer. The transformer is likely mounted on or near the furnace. It should have 120VAC going into it, and ~24VAC coming out. Some furnaces have a fuse (typically ~3A) in the transformer circuit to protect the transformer in the event of a short circuit.

So, check for 24VAC at the thermostat and report back what you find.
 
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Old 07-06-15, 03:31 AM
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Also test from R red to G green . It should have 24 VAC , also .

The wires terminated at the tstat should go to a terminal strip at the furnace . Or a group of small low voltage wires at the tstat .

This is an electronic tstat ?

God bless
Wyr
 
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Old 07-07-15, 12:30 PM
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Thanks guys. As luck would have it a storm came through, downed several trees and power lines in my yard...left me with no power for quite a while. I'll be home to check the thermostat shortly. I did want to mention that the tank on the condensate pump was full. I emptied it, made no difference. Should I refill it? Leave it empty? I'll post my thermostat readings a couple hours.
Thanks again
Steve
 
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Old 07-07-15, 01:36 PM
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Leave it empty. Does the pump have a cutout switch?
 
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Old 07-10-15, 06:18 AM
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Okay, I tested voltage from the Rc-Y, and Rh-Y. No voltage. There's a 3amp fuse on the circuit board, but it appears fine. There's a green light on the board that indicates power is coming to the board. The condensate pump does have a cutout switch, but it is on. Any more ideas? Thanks!
 
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Old 07-10-15, 07:14 AM
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Did you test the voltage from R to Y and R to G with the thermostat turned OFF? If so, there appears to be no 24VAC present. However, if the thermostat was ON and calling for cooling, these voltages are normal.

Here's something else you can check. Go down to your furnace and find where the thermostat wires connect to the furnace control board. If I have the correct manual for your furnace, you should see terminals marked Y, G, W, R, C near the 3A fuse. Use your voltmeter and check for voltage between R & C. You should measure ~24VAC. Note that you'll have to tape the door interlock switch. This switch turns off the power to the furnace when you remove the cover/door that covers the blower & control board area. Press the switch "in" and tape it in that position so that the furnace is powered up for this test.

Let us know what you read.
 
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Old 07-10-15, 04:48 PM
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The furnace door switch is taped, power good to the board. When checking power between terminals R - C, I'm good there. I think it read 28v, but yes I'm hot there. I also checked the wires coming out of the wall, going into the thermostat (yes, it's digital/programmable...have changed batteries, also put it in standard, non-programmable mode) I have nothing testing R-Y, nothing R-G either.
 
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Old 07-10-15, 04:57 PM
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If your thermostat easily removes from it's mounting plate (most newer thermostats "plug in" to a mounting plate with the wires attached to the mounting plate), remove it. At the furnace (door switch taped so power is on), temporarily jumper the following thermostat wires:

R to Y - Outside unit should turn on
R to G - The furnace blower should turn on
R to G & Y - Both the furnace blower and the outside unit should turn on, giving cooling

If the system works as described, you either have bad thermostat wiring or the thermostat is bad. To check the thermostat wiring, jumper the above wires, this time at the thermostat terminals rather than the furnace control board. If the furnace blower & outside unit turn on, the thermostat is defective. If either don't turn on, then you likely have a broken thermostat wire, most likely the R wire.
 
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Old 07-12-15, 11:57 AM
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This thing has a mind of its own. Now I can't seem to get power back to the board. I came down to test power between terminals on the board and the cover safety switch had pushed the tape off itself. I pressed the switch in, the led on the board lit briefly and went out. No breakers blown in the service panel, the fuse on the board still looks good too. I pulled out and then replaced the outside disconnect Any ideas where else I should check? Think that safety switch just went bad?
Thank you so much for your help!
Steve
 
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Old 07-12-15, 12:11 PM
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It's unlikely that the cover switch went bad, however anything is possible. I would suggest that you remove the fuse and check it with an ohmmeter. If the fuse is good, shut down the power to the furnace and check the switch with an ohmmeter (make sure the power is off before touching any terminals on the cover switch).
 
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