Buzzing contactor and NO A/C
#1
05-06-19, 07:11 PM
Buzzing contactor and NO A/C
so I noticed that the blower and all was working but it wasn’t cool. Went outside and the condenser was making a low buzzing/humming sound. The fan wouldn’t kick nor the compressor. Tested for 24v and got 26.6v so I moved in to the 240 and was not getting anything on the 240. Moved to the disconnect and got 96v reading on it. Moved to the breaker and top pole read 120 and bottom read 26.4. My questions are as follows:
1. Why no reading at all at the contactor?
2. Why 96v at the disconnect?
3. I need to start by replacing the breaker, right?
1. Why no reading at all at the contactor?
2. Why 96v at the disconnect?
3. I need to start by replacing the breaker, right?
#2
05-06-19, 07:57 PM
Group Moderator
Welcome to the forums.
Actually the buzzing you are hearing is not the contactor. It's the compressor and fan humming from low voltage. Don't leave the A/C running on low voltage.
Yes..... that would indicate a defective circuit breaker or a bad connection to the bus bars.
You need to measure 240vAC across the two pole breaker.
Carefully remove the breaker and examine the lugs on the back of it. Check the lugs for burning. You can also visually inspect the bus bars inside the panel but DON'T touch them as they are live.
Actually the buzzing you are hearing is not the contactor. It's the compressor and fan humming from low voltage. Don't leave the A/C running on low voltage.
Yes..... that would indicate a defective circuit breaker or a bad connection to the bus bars.
You need to measure 240vAC across the two pole breaker.
Carefully remove the breaker and examine the lugs on the back of it. Check the lugs for burning. You can also visually inspect the bus bars inside the panel but DON'T touch them as they are live.
#3
05-07-19, 04:30 AM
Member
It sounds like your checking voltage to ground.
Check across the circuit instead. Checking to ground can give you false readings.
Check across the circuit instead. Checking to ground can give you false readings.
#4
05-11-19, 06:35 PM
So I replaced the breaker and then discovered the fuses in the disconnect were blown. Replaced those and the fan came on but was spinning very slow. Shut it down and replaced the capacitor. I now have 240 coming all the way through the contactor but am still getting nothing from the compressor or fan. I even tried bypassing the defrost board to see if I could get the fan to engage and it wouldn’t come on.
#5
05-11-19, 06:43 PM
Group Moderator
Did you check for 240vAC at the equipment side of the contactor ?
That would be the side that is live when the contactor closes.
That would be the side that is live when the contactor closes.
#7
05-11-19, 07:53 PM
Group Moderator
Just to confirm.... not the side of the contactor where incomimg power connects.
The side that goes to the fan and compressor.
If there was 240v across the output of the contactor..... the compressor and fan should be at least humming.
It would be doubtful that the fan motor and compressor both went bad. I'd have to think a wire may have fallen off. Possibly off the contactor or the capacitor.
The side that goes to the fan and compressor.
If there was 240v across the output of the contactor..... the compressor and fan should be at least humming.
It would be doubtful that the fan motor and compressor both went bad. I'd have to think a wire may have fallen off. Possibly off the contactor or the capacitor.
#9
05-12-19, 06:40 PM
Novice... I am getting 120 at each leg to ground and the same on the other end of the contactor. Starting reading and digging and I think I may actually have a burned up disconnect. I’m getting 240 into the disconnect and 120 out each leg but Nothing combined.
#11
05-13-19, 12:04 AM
Group Moderator
I did.... 240 across the contactor
You MUST get 240vAC at any place where it should be.
Into the disconnect........ out of the disconnect.
Into the contactor......... out of the contactor.
#12
05-13-19, 07:52 AM
As Roughneck stated I was checking them to ground instead of across the circuit. When I check across the circuit I get nothing. When I check each side to ground I get 120 on each.
#13
05-13-19, 08:18 AM
Member
So you have a leg of power out.
You may have something grounded and that’s why the fan is spinning very slowly. If so use a lot of care. If your equipment isn’t properly grounded, the cabinet can become energized and kill you when you touch it.
There’s been documented cases of techs loosing their lives like this.
You may have something grounded and that’s why the fan is spinning very slowly. If so use a lot of care. If your equipment isn’t properly grounded, the cabinet can become energized and kill you when you touch it.
There’s been documented cases of techs loosing their lives like this.
#14
05-13-19, 08:31 AM
I could see one of the contacts in the disconnect is burnt and looks like it may have some corrosion. I’m getting the 240 coming in to the disconnect but am not getting the 240 across the circuit going out of the disconnect only 120 per leg.
#17
05-13-19, 04:20 PM
Group Moderator
Do you have 240vAC where the wiring enters the disconnect ?
Do you have 240vAC where the wiring leaves the disconnect ?
Do you have 240vAC where the wiring leaves the disconnect ?
#19
05-13-19, 05:06 PM
Member
So was the fuse open when you bought it, or did it open when you restored power to the equipment?
#20
05-13-19, 06:18 PM
I honestly don’t know since I didn’t test them before putting them in. The indicator on the fuse doesn’t show that it is blown. What would that mean if I put new ones on and one blows?
#21
05-13-19, 06:29 PM
Member
It would mean you have a short on that leg, or something is wrong and causing a current draw higher then the fuse rating.
Have you checked the fuse with your meter to see if it’s actually open?
Have you checked the fuse with your meter to see if it’s actually open?
#25
05-13-19, 07:09 PM
Member
So now you’ll have to determine if the fuse was open when you bought it or something caused it to blow.
#26
05-13-19, 07:21 PM
Took them back to HD and swapped them. Put the new ones in and waited for the delay and the condenser started up! Went upstairs waiting for the cooling to start and heard a pop. Checked the air handler and the capacitor to the blower fan popped. It was already swollen so not sure if the other issues are to blame??
#28
05-13-19, 07:50 PM
Actually had the correct capacitor that I saved from the Frankenstein capacitor someone built for the condenser. Put that one on the blower and it is now blowing 3 times better than before. Problem now is no cooling... I can feel heat coming from the evaporator in the handler....
