No power in external A/C Unit - Please help
#1
06-14-17, 07:26 AM
No power in external A/C Unit - Please help
Hello Everyone,
I reduced the temperature at thermostat to Cool (50 Deg F), Thermostat clicked and furnace is running, air blow out in vents but external AC unit is not working,
I checked at connector there is no power/voltage in wires coming from inside.
Checked at the main electrical panel board and voltage is there at AC switch.
Could you please help in troubleshooting this issue.
Thanks in advance.
I reduced the temperature at thermostat to Cool (50 Deg F), Thermostat clicked and furnace is running, air blow out in vents but external AC unit is not working,
I checked at connector there is no power/voltage in wires coming from inside.
Checked at the main electrical panel board and voltage is there at AC switch.
Could you please help in troubleshooting this issue.
Thanks in advance.
#3
06-14-17, 07:47 AM
'Disconnect fused' sorry not got this point..
At the external unit there is box disconnect and there is a fuse (Big plug that can be pulled out) but I checked there is no voltage incoming from inside (to that box). Hope I am clear
At the external unit there is box disconnect and there is a fuse (Big plug that can be pulled out) but I checked there is no voltage incoming from inside (to that box). Hope I am clear
#4
06-14-17, 07:56 AM
Member
Some disconnect switches have fuses for current protection. If your disconnect is not receiving line voltage, you'll have to trace the circuit back towards the panel and see where the open circuit is. Since you've already verified the breaker is putting out the correct voltage.
#5
06-14-17, 08:06 AM
Thanks roughneck77 for your quick responses. Appreciated.
>> you'll have to trace the circuit back towards the panel and see where the open circuit is
All the wiring is underground, not sure how to trace it back, any idea on this please?
>> you'll have to trace the circuit back towards the panel and see where the open circuit is
All the wiring is underground, not sure how to trace it back, any idea on this please?
#6
06-14-17, 08:12 AM
Member
It's underground leading from the circuit box in the house to the disconnect for the outdoor unit?
#7
06-14-17, 08:26 AM
Yes roughneck77. Its underground from circuit box itself.
From external disconnect also all wiring is underground, in between does it go to furnace as well?
From external disconnect also all wiring is underground, in between does it go to furnace as well?
#8
06-14-17, 08:36 AM
Member
The power to the furnace should be separate from the condenser supply unless you have a packaged unit.
Power should leave the condenser disconnect and run directly to the circuit breaker. Unless it's a manufactured home which then it may be powered off a circuit breaker outdoors.
Power should leave the condenser disconnect and run directly to the circuit breaker. Unless it's a manufactured home which then it may be powered off a circuit breaker outdoors.
#9
06-14-17, 10:09 AM
If you checked voltage with a non contact tester the reading is meaningless. You need to use a multimeter, neon test light, or a solenoid voltage tester.
First you need to reset the 240 volt breaker for the condenser (outside unit) by turning it all the way off then back on.
Almost certainly an unfused disconnect which is common on residential A/Cs. Using a multimeter you need to measure the incoming voltage at the two side by side lugs. There should be two sets of two lugs. It should read ~240v. If no reading you should try measuring each lug to ground. You should get ~120 volts.
Post a picturer of the inside of the disconnect with the internal cover removed if you need more help measuring. http://www.doityourself.com/forum/li...rt-images.html
First you need to reset the 240 volt breaker for the condenser (outside unit) by turning it all the way off then back on.
At the external unit there is box disconnect and there is a fuse (Big plug that can be pulled out)
Post a picturer of the inside of the disconnect with the internal cover removed if you need more help measuring. http://www.doityourself.com/forum/li...rt-images.html
#10
06-14-17, 11:38 AM
If you checked voltage with a non contact tester the reading is meaningless.
You need to use a multimeter, neon test light, or a solenoid voltage tester.
First you need to reset the 240 volt breaker for the condenser (outside unit) by turning it all the way off then back on.
Post a picturer of the inside of the disconnect with the internal cover removed if you need more help measuring.
#11
06-14-17, 12:00 PM
The power to the furnace should be separate from the condenser supply unless you have a packaged unit.
Just for my understanding, when we reduce the temprature at thermostat how external AC unit comes to know about this and how it gets triggered in the whole process.
#14
06-14-17, 05:15 PM
Post a picturer of the inside of the disconnect with the internal cover removed if you need more help measuring.
Last edited by PJmax; 06-14-17 at 08:57 PM. Reason: reoriented pictures
#18
06-14-17, 07:19 PM
Sorry but that doesn't make sense. Line means power from the house. One cable should come fro the house breaker panel. The other should go to the condenser. The disconnect you show should be on the side of the house and have a cable from the breaker panel that reads 240 volts. That is line.
From the air handler in the attic there should be a 18 gauge thermostat cable. Your picture is not a thermostat cable and that is not what we are concerned with right now.
From the air handler in the attic there should be a 18 gauge thermostat cable. Your picture is not a thermostat cable and that is not what we are concerned with right now.
Last edited by ray2047; 06-14-17 at 07:50 PM.
#19
06-14-17, 08:00 PM
Thanks for the explanation ray2047.
I got your point and had meant the same but probably I was not able to explain it properly.
In the lines you labelled - power comes in cable A and goes to condenser through cable B.
From air handler where this thermostat cable goes to ?
I will get the meter for further testing tomorrow and will post the outcome here.
I got your point and had meant the same but probably I was not able to explain it properly.
In the lines you labelled - power comes in cable A and goes to condenser through cable B.
From air handler where this thermostat cable goes to ?
From the air handler in the attic there should be a 18 gauge thermostat cable.
I will get the meter for further testing tomorrow and will post the outcome here.
#24
06-16-17, 07:33 PM
Is their any voltage anywhere in the disconnect? Between any of the terminals?
#27
06-16-17, 07:58 PM
Put one probe on ground and the other probe on one of the four wires/terminals.
Does it matter where we put Red/Black (+ve/-ve) probe?
#28
06-16-17, 08:11 PM
Does it matter where we put Red/Black (+ve/-ve) probe?
Just saw an unanswered question of yours:
First you need to reset the 240 volt breaker for the condenser (outside unit) by turning it all the way off then back on.
Last edited by ray2047; 06-16-17 at 09:11 PM.
#29
06-17-17, 05:35 AM
Put one probe on ground and the other probe on one of the four wires/terminals.
Please advise
Your breaker in in your breaker box. You did turn it all the way off then on didn't you?
#30
06-17-17, 06:12 AM
Group Moderator
Please post a picture of your electrical panel with the door open so we can see the breakers. If you are comfortable with working around hot wires, shut off the main breaker of the electrical panel, take a picture of the inside and post that as well. Even with the main breaker off, there are still hot wires inside so caution is required! 
Also post a picture of the electrical meter you bought and what setting you are using it on.
Thanks!
Also post a picture of the electrical meter you bought and what setting you are using it on.
Thanks!
#31
06-17-17, 12:24 PM
I have done the probe on the ground but there also is no voltage
