Condenser Unit Troubleshoot - HVAC - DIY Chatroom Home Improvement Forum
Advertisement


Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > HVAC

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Search this Thread
Display Modes
Old 09-07-2020, 05:10 PM   #1
Newbie
 
Join Date: Jun 2006
Posts: 25
Rewards Points: 42
Default

Condenser Unit Troubleshoot


Condenser unit in an 8 year old split system is getting adequate voltage on the load side of the contactor, but won't start. Seems to want to (i.e., it makes a buzzing/hissing sound before I shut it off). Fan doesn't spin either.

What is the suggested diagnostic path from here? I'd like to rule out any simple-to-identify causes before I call in help.

Checking the capacitor is next?

Thanks.

Last edited by Riddler; 09-07-2020 at 05:39 PM.
Riddler is offline   Reply With Quote
Sponsored Links
Advertisement
 
Old 09-07-2020, 05:26 PM   #2
Member
 
Join Date: Nov 2014
Posts: 5,836
Rewards Points: 716
Default

Re: Condenser Unit Troubleshoot


Is this a heat pump or straight air conditioner?
Is it getting control voltage? Contactor pulling in? Power on both poles?
roughneck is online now   Reply With Quote
Sponsored Links
Advertisement
 
Old 09-07-2020, 05:45 PM   #3
Newbie
 
Join Date: Jun 2006
Posts: 25
Rewards Points: 42
Default

Re: Condenser Unit Troubleshoot


Straight A/C

Control voltage is fine. Contactor is working to deliver full voltage on the load side.

Attached (hopefully) is a pic of the capacitor. Because the condensor hums and the fan doesn't turn, maybe toubleshoot the cap next? The cap has three wires. The yellow comes from the load side of contactor. The blue and brown go into the condenser housing, probably to the motor, correct?

Discharge the cap and then test it with a VOM?
Attached Thumbnails
Condenser Unit Troubleshoot-ac-cap.jpg  
Riddler is offline   Reply With Quote
Sponsored Links
Advertisement
 
Old 09-07-2020, 06:04 PM   #4
Member
 
Join Date: Nov 2014
Posts: 5,836
Rewards Points: 716
Default

Re: Condenser Unit Troubleshoot


Yes, test the capacitor.
roughneck is online now   Reply With Quote
Old 09-08-2020, 10:34 AM   #5
Member
 
Join Date: Oct 2010
Posts: 322
Rewards Points: 344
Default

Re: Condenser Unit Troubleshoot


Test your Cap with a MF meter, not VOM.
clocert is offline   Reply With Quote
Old 09-08-2020, 11:13 AM   #6
Member
 
Join Date: Nov 2014
Posts: 5,836
Rewards Points: 716
Default

Re: Condenser Unit Troubleshoot


Quote:
Originally Posted by clocert View Post
Test your Cap with a MF meter, not VOM.
A lot of general use meters have a capacitance function. No need for a specific one use only device.
But the OP will need a meter capable of reading capacitance.
roughneck is online now   Reply With Quote
Old 09-08-2020, 12:05 PM   #7
Newbie
 
Join Date: Jun 2006
Posts: 25
Rewards Points: 42
Default

Re: Condenser Unit Troubleshoot


Well, my meter only measures ohms, not MFD.

I set my DMM to the highest ohm setting (2000K).

On the Herm and C terminals, the reading rose from 0 to 1220, and stopped. Not sure why it didn't discharge and return to 0 for another climb.

On the Fan and C terminals, reading didn't move. Stayed at 0.

The cap ratings by the way are 40 MFD compressor side and 5 MFD fan side.

Anyway, weird enough that I'll go ahead and invest $35 to get a replacement by 2-day courier.
Riddler is offline   Reply With Quote
Old 09-08-2020, 12:22 PM   #8
Newbie
 
Join Date: Jun 2006
Posts: 25
Rewards Points: 42
Default

Re: Condenser Unit Troubleshoot


If the new cap doesn't cure things, what next.

As I said, when the contactor juices things, there is a clunk followed by a buzz/hum. Neither compressor or fan runs though. Same thing every time I flip the disconnect to "on."

The applicable wiring diagram (attached) seems to show a separate start cap and relay (or thermistor) as included on some units, but I don't see any on mine. Can a 2 1/2 ton condensor unit only have a dual run cap? How do they get the compressor started? It's frustrating that the only parts and wiring diagrams I can find don't tell me exactly how my particular model/unit is set up. The manufacturer (Day/Night) only bothers to make generalized diagrams that are supposed to apply to a group of models/units.
Attached Thumbnails
Condenser Unit Troubleshoot-ac-wiring.jpg  
Riddler is offline   Reply With Quote
Old 09-08-2020, 01:20 PM   #9
Member
 
Join Date: Nov 2014
Posts: 5,836
Rewards Points: 716
Default

Re: Condenser Unit Troubleshoot


You sure you have power to the condenser? The hum may just be the contactor coil.
roughneck is online now   Reply With Quote
Old 09-08-2020, 01:29 PM   #10
Member
 
surferdude2's Avatar
 
Join Date: Nov 2019
Location: Southern Illinois, USA
Posts: 2,945
Rewards Points: 896
Default

Re: Condenser Unit Troubleshoot


Quote:
Originally Posted by Riddler View Post

The applicable wiring diagram (attached) seems to show a separate start cap and relay (or thermistor) as included on some units, but I don't see any on mine. Can a 2 1/2 ton condensor unit only have a dual run cap? How do they get the compressor started? It's frustrating that the only parts and wiring diagrams I can find don't tell me exactly how my particular model/unit is set up. The manufacturer (Day/Night) only bothers to make generalized diagrams that are supposed to apply to a group of models/units.
The diagram is likely correct. Those items you refer to are options that the factory may or may not have installed according to the notes on the bottom there. Those are hard start components not usually needed on most applications.

Your capacitor is shown in that vertical rectangle box and is a dual unit. 40-5 Microfarads.

If you have no meter with a capacitor checker in it, you can do a rough/crude test with a multimeter. The 40 Mfd. section from C to H terminals should show some continuity for a few seconds and then settle down to a zero reading (Infinity). Same for the 4 Mfd. ( C to F) one but much quicker happening. Have the wire/wires disconnected from the C terminal for those tests.
__________________
Ah, but I was so much older then...I'm younger than that now

Last edited by surferdude2; 09-08-2020 at 01:35 PM.
surferdude2 is offline   Reply With Quote
Old 09-08-2020, 03:14 PM   #11
Newbie
 
Join Date: Jun 2006
Posts: 25
Rewards Points: 42
Default

Re: Condenser Unit Troubleshoot


Roughneck, the noise is not coming from the contactor. The contactor coil operates fine (i.e., sucks in the switch complete when control voltage is applied). I have also confirmed full operating voltage on the load side of the contactor.

Surfer, please see my previous post describing the results of my DMM "ohms only" testing.

I'll pop in the replacement cap in a few days and report back. Not sure that will do it, but I want to eliminate the cap as a possible cause.
Riddler is offline   Reply With Quote
Old 09-08-2020, 03:15 PM   #12
Newbie
 
Join Date: Jun 2006
Posts: 25
Rewards Points: 42
Default

Re: Condenser Unit Troubleshoot


Roughneck, the noise is not coming from the contactor. The contactor coil operates fine (i.e., sucks in the switch completely when control voltage is applied). I have also confirmed full operating voltage on the load side of the contactor.

Surfer, please see my previous post describing the results of my DMM "ohms only" testing.

I'll pop in the replacement cap in a few days and report back. Not sure that will do it, but I want to eliminate the cap as a possible cause.
Riddler is offline   Reply With Quote
Old 09-08-2020, 04:17 PM   #13
Member
 
surferdude2's Avatar
 
Join Date: Nov 2019
Location: Southern Illinois, USA
Posts: 2,945
Rewards Points: 896
Default

Re: Condenser Unit Troubleshoot


Quote:
Originally Posted by Riddler View Post

Surfer, please see my previous post describing the results of my DMM "ohms only" testing.

I'll pop in the replacement cap in a few days and report back. Not sure that will do it, but I want to eliminate the cap as a possible cause.
I missed that... based on it not going all the way to infinity on the Hermatic and nowhere at all on the Fan, I say you need a new cap. Lucky. The common leg must be flaky... no buldging though. Goes to show they don't always fry and swell up.
__________________
Ah, but I was so much older then...I'm younger than that now
surferdude2 is offline   Reply With Quote
Old 09-08-2020, 04:43 PM   #14
A "Handy Husband"
 
rjniles's Avatar
 
Join Date: Feb 2007
Location: South Carolina Low Country
Posts: 11,602
Rewards Points: 42
Default

Re: Condenser Unit Troubleshoot


Buy a new capacitor and try it, they are cheap- under $20

https://smile.amazon.com/Genteq-97F9...601220&sr=8-13
__________________
My electrical answers are based on 2017 NEC, you may have local amendments.

Location: Coastal South Carolina
rjniles is online now   Reply With Quote
Sponsored Links
Advertisement
 
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off





Top of Page | View New Posts