Compressor and Fan Not Working After New Contactor Installed

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Old 11-02-19, 07:04 PM
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Compressor and Fan Not Working After New Contactor Installed

About two weeks ago my American Standard (2011 model) stopped producing cold air AND hot air. The blower in the outside unit operates normally and air is flowing through the vents inside.

So I got to reading some posts on here about a possible bad contactor. So I took off the electrical panel to the unit (with power to it) and pushed in the contacts manually. I know it's not safe to do this but the fan and compressor turned on just fine. Then when the contacts were released they shut off.

The contactor is getting 240 VAC to the lines and also 240VAC come out on the T side when manually pushed in.

When checking for 24 VAC between the contractor coil I get no voltage reading. Also I get no ohm reading. Just "OL". So I went out and bought a replacement with the exact specs. I get about 15 ohms on the new contactor and installed it paying careful attention to the wiring.

Well it's still not working. I still don't get 24VAC voltage across the new contactor's coil. Could it be a bad transformer? Capacitor looks to be in good condition as well. I don't see any burnt fuses.

Thanks in advance!
 
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Old 11-02-19, 07:16 PM
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The Honeywell digital thermostat seems to be working fine, too. The Aux Heat kicks on when setting the temp 5 or more degrees higher than inside temp as well.
 
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Old 11-02-19, 08:27 PM
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No 24V means the contactor wasn’t the problem.
It’s the voltage source.
You’ll have to test to see if the thermostat is calling for the compressor to run. Then move on to the defrost board.
 
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Old 11-02-19, 08:39 PM
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BTW...OL on your meter probably means overload. Or in the resistance setting...likely it means open circuit or no continuity.
 
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Old 11-03-19, 06:59 AM
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Thanks roughneck. I have checked the R and Y terminals at the thermostat and I get about 27 VAC. Should I check other terminals at the thermostat?
 
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Old 11-03-19, 07:02 AM
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While it’s calling you get 27V?
That’s your problem, you have voltage between R and Y. It’s not calling to run.
 
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Old 11-03-19, 08:21 AM
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Roughneck, if I let the thermostat call for cooling and then detach the outer panel will it still be trying to call for cooling? It won't shut off with the thermostat detached?
 
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Old 11-03-19, 08:32 AM
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The thermostat needs to be attached.
 
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Old 11-03-19, 10:12 AM
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How do you test anything while it's attached? You cannot access any terminals while the face is attached to the wall.
 
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Old 11-03-19, 10:14 AM
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You have to test at the equipment.
This is where you have to be comfortable working around live electricity. As you will be exposed to both high and low voltage conductors.
Test the thermostat wiring at the air handler.
 
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Old 11-03-19, 10:24 AM
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The blower in the outside unit operates normally and air is flowing through the vents inside.
Is this a mistype or do you have a packaged unit ?
 
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Old 11-03-19, 10:43 AM
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Packaged unit, PJ. It's all contained in the outdoor unit.
 
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Old 11-03-19, 10:45 AM
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Ok, go to the low voltage terminal block. Is there a call for the unit to run there?
 
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Old 11-03-19, 12:21 PM
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Roughneck, please forgive my ignorance. Where is the low voltage terminal block?
 
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Old 11-03-19, 12:23 PM
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It’s where the thermostat wires connect inside the unit.
 
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Old 11-03-19, 12:43 PM
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Here is what my electrical panel on the inside looks like. Could you point me in the right direction?
 
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Old 11-03-19, 12:46 PM
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On the right in the box with the wire nuts.
 
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Old 11-03-19, 01:01 PM
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I found a black and brown wire not connected. Should these be tied into one of these wire nuts?
 
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Old 11-03-19, 01:03 PM
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No, probably just unused conductors in the bundle.
 
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Old 11-03-19, 01:05 PM
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Ok, how do I test these wires? What am I looking for?
 
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Old 11-03-19, 01:07 PM
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Use your meter. Are you getting a call or not?
 
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Old 11-03-19, 01:10 PM
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I guess I'm asking how to use the meter to test the wiring? Do I remove the wires from the nuts exposing them and touching the leads to the bare copper?
 
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Old 11-03-19, 02:17 PM
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So the yellow wire on the right side of the contactor coil is reading 27VAC when grounded to the metal frame. Also the blue wire on the left side of the coil reads 27 VAC when grounded. The other blue wire does not read any voltage but when I touch the terminal of this wire to the contactor I hear a "click" then silence. Also the LED on the circuit board next to the contactor starts to blink every second.

Any thoughts?
 
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Old 11-03-19, 03:07 PM
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Roughneck, since I'm getting 27 volts from the wires that connect on either side of the contactor coil I think it's calling for cooling from the thermostat.

Check the defrost board?
 
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Old 11-03-19, 04:40 PM
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Test across the circuit, not to ground. Y to C.
 
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Old 11-03-19, 06:24 PM
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What exactly do I do to test across the circuit?
 
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Old 11-03-19, 06:34 PM
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Your testing for voltage across the circuit.
 
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Old 11-03-19, 07:45 PM
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Yes but what do I do with the probes on my meter? Stick the black one in the Y wire and the red one in the C wire?

Sorry I'm really new to this type of work.
 
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Old 11-03-19, 08:05 PM
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Doesn’t matter as far as meter probe colors. This is ac voltage.
 
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Old 11-04-19, 04:17 PM
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Roughneck, the Y and C wires are giving me 27 volts as a circuit. They were disconnected from the contactor when tested.

Is that good or bad? I would think you would want voltage in these wires to activate the contactor coil.
 
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Old 11-04-19, 04:27 PM
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Ok..... make sure the power is off to the condenser.
Reconnect the wires to the contactor and measure them on the contactor.
You want to see if the contactor is loading the circuit.
 
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Old 11-04-19, 04:38 PM
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PJ, I get 14.7 ohms across the contactor coil with the wires attached. I do not get voltage which makes sense because I threw the disconnect.
 
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Old 11-04-19, 04:50 PM
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The Y voltage comes from inside the house. It should be there even when the condenser is powered down.
Leave the condenser powered down. Check for 24vAC at the yellow and blue connections where the wirenuts are. You should be able to stick your probes inside the wirenuts.

Also check from red to blue for 24v.
 
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Old 11-04-19, 04:52 PM
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Is this a packaged unit or split?
 
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Old 11-04-19, 04:56 PM
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roughneck, it's a package unit.
 
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Old 11-04-19, 05:13 PM
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PJ, do I insert both probes in one wire nut to test for VAC?
 
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Old 11-04-19, 05:18 PM
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You put one probe in red and one probe in blue...... what do you get ?
Put one probe in yellow and one probe in blue.... what do you get ?
 
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Old 11-04-19, 05:20 PM
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Ok I'll check it tomorrow when I have some daylight.

Thanks!
 
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Old 11-04-19, 05:42 PM
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You need to measure 24v on the red and blue at all times.
There will only be 24v on yellow and blue when the stat is calling for cooling.

If you don't get any voltage on the red and blue..... you have lost your 24v source in the air handler.
 
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Old 11-06-19, 03:47 PM
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PJ, I am not getting any voltage on the red and blue wire nuts.

How can this happen and how to fix it?
 
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