Compressor and Fan Not Working After New Contactor Installed
#1
11-02-19, 07:04 PM
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!
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!
#3
11-02-19, 08:27 PM
Member
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.
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.
#4
11-02-19, 08:39 PM
Super Moderator
BTW...OL on your meter probably means overload. Or in the resistance setting...likely it means open circuit or no continuity.
#6
11-03-19, 07:02 AM
Member
While it’s calling you get 27V?
That’s your problem, you have voltage between R and Y. It’s not calling to run.
That’s your problem, you have voltage between R and Y. It’s not calling to run.
#7
11-03-19, 08:21 AM
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?
#10
11-03-19, 10:14 AM
Member
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.
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.
#11
11-03-19, 10:24 AM
Group Moderator
The blower in the outside unit operates normally and air is flowing through the vents inside.
#23
11-03-19, 02:17 PM
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?
Any thoughts?
#24
11-03-19, 03:07 PM
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?
Check the defrost board?
#30
11-04-19, 04:17 PM
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.
Is that good or bad? I would think you would want voltage in these wires to activate the contactor coil.
#31
11-04-19, 04:27 PM
Group Moderator
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.
Reconnect the wires to the contactor and measure them on the contactor.
You want to see if the contactor is loading the circuit.
#33
11-04-19, 04:50 PM
Group Moderator
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.
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.
#37
11-04-19, 05:18 PM
Group Moderator
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 ?
Put one probe in yellow and one probe in blue.... what do you get ?
#39
11-04-19, 05:42 PM
Group Moderator
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.
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.
