HVAC-Talk: Heating, Air & Refrigeration Discussion banner
Cancel
Create thread New Forums

Compressor Turning on and off! Idk what’s going on!

Jump to Latest
1 - 20 of 34 Posts
J

Jricehvac

· Registered
Joined
·
11 Posts
Discussion starter · #1 ·
Went to a customers house today with an older Carrier AC with no AC. unit was Maybe from 2004 or so. Turned thermostat on, checked furnace filter and blower motor they were fine. Went down to AC 5 mins after I turned AC on and as soon as I get down the compressor decides to kick on (OD fan was already on) took disconnect out and checked internal parts. Capacitor is ok, contractor is ok. Put the disconnect back in and again only the condenser fan kicked on but no compressor. Took disconnect back out again waited 5 mins and threw it back in and the fan and compressor both turn on. Checked the pressures while I had the chance. They were fine. Got 240 into the contactor and out. MFDs on dual cap were fine. All connections are secure including terminals at compressor. Checked the ohms between terminals at compressor and nothing was open, also megged compressor and all winding are fine. Yet when I put the disconnect back in again compressor again does not turn on. Contactor never stopped pulling in and I could not find a high pressure switch on refrigeration circuit.
-pressures are good
-contactor and capacitor are fine.
-compressor is not on thermal overload
-voltages are fine
The only thing I noticed that was weird was when the compressor was not running I only got 120 between Herm and common on the capacitor and when the compressor was running I was getting 240 between common and herm.
What is casuing this intermittent problem?? Please help!!
 
Discussion starter · #5 ·
No the compressor is turning on and off. I was able to check them while the compressor was running. Amp draw is a little high but not over amping. And yes the contactor was pulled in the whole time I was there. No low volt issues
 
Discussion starter · #6 ·
the compressor is turning on and off. I was able to check them while the compressor was running. Amp draw is a little high but not over amping. And yes the contactor was pulled in the whole time I was there. No low volt issues
 
#7 ·
That's weird. Only thing I can suggest from here is OHM out the compressor from the wires that are connected to your uncap and the contactor if you have not done that already. Maybe the wiring is is bad for the start winding from the run capacitor to the compressor.

Sent from my SM-J700T using Tapatalk
 
#10 ·
Sounds to me like there was a compressor time delay initially, and then every time you attempted to restart, the compressor was loaded and tripped IOL, which is normal on a recip compressor. The voltage between Herm and Common on the capacitor will be 0V if it's not running, and likely over 300V when it's running. If you're only getting 240V across the capacitor terminals when it's running, it's not getting up to full speed, and or not getting full voltage. The only things I can think of if you're getting 120V across the capacitor when it's not running is trickle current acting like a sump heater, leakage to ground somewhere, or poor input voltage under load due to failing breaker.
 
Save
Like Like
#12 ·
My first thought is there is a time delay in the circuit that you have not seen or found.
Second thought capacitor going bad
Third thought bad thermal (klixon) overload on the compressor (if it does not have one the interanl motor overload going bad)
Fourth thought loose wire bad connection

Good Luck
 
#13 ·
Unless wired differently the capcitor is only fed by one side of the contactor so you'd only see 120. Like others have said you most likely have a thermal overload opening on the common leg of the compressor, or a loose/bad terminal

Sent from my XT1710-02 using Tapatalk
 
#14 ·
Just asking because I did not see if you stated, but are you really sure the contactor is good. (same voltage and amps on in and out). Had one last week that would hang up and not always make contact on each leg even though it was visually pulled in.
 
Discussion starter · #16 ·
Yes contactor is receiving 240 in and out. Even decided to be a part changer and just replaced it to see if it would make a difference and it did not. I’m going back tomorrow to do some more investigating. Also installing a start kit for the hell of it too. I’ll keep what you said in mind from your last comment. Thanks
 
#17 ·
To me you reading 120 across the capacitor contacts seems like an internal overload tripped with a partial short to ground. Did you check amps on the compressor when it was not running?

The start and/or run windings sorted to ground with the common opened is the only way you could get voltage of 120 on the cap with no turning or buzzing or anything in my opinion.


Sent from my iPhone using Tapatalk
 
1 - 20 of 34 Posts
You have insufficient privileges to reply here.
About this Discussion
33 Replies
15 Participants
Last post:
mgenius33
HVAC-Talk: Heating, Air & Refrigeration Discussion
posts
5M
members
275K
Since
2000
The #1 HVACR Community
Full Forum Listing
Explore Our Forums
AOP Residential HVAC/Refrigeration(Beenthere Zone) General Discussion Tech to Tech Chat - Residential Controls Refrigeration & Ice Making