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unit locking up

but...2 ton ac..11 yrs old. unit will start and run .. comp. amps 7 ..fan 2.2 ..volts 236 ... 208 hd 80 back ..80 inside temp...unit sounds good
after 15 min the whole unit slows down and stops ..cc still pulled in ... run load amps never changed until stopped completely than goes to zero...it takes 5 sec. once it starts slowing down before it winds down and stpos .i watched incoming power as well it goes unchanged...any ideas? thanks



davidg
Good Bye My Friend
Premium,MVM
join:2002-06-15
none

could be a bad run cap or a bad fan motor.


my apology...i put a new stack cap. it did it again... i also did it with two individual capacitors and again both compressor and fan slowed down and stopped completely



pende_tim
Premium
join:2004-01-04
Andover, NJ
kudos:1
Reviews:
·Comcast

1 recommendation

reply to Busted bayou

Are the contacts in the main contractor clean? Have you checked for loose power feed connections?
"Whole unit slowing down" sounds like it is loosing power slowly like a high resistance in the power feed.
--
The difference between genius and stupidity is that genius has its limits.


reply to Busted bayou

i did check the tightness of lugs at breaker...i didnt replace contactor..it seemed alright. there could more going on there than meets the eye..
I let u know...thanks



pende_tim
Premium
join:2004-01-04
Andover, NJ
kudos:1
Reviews:
·Comcast

1 edit

There should be at least 3 more connection points to check in addition to the breaker:
1. Into the local disconnect
2. Out of the local disconnect
3. Where the power lands in the unit.

Did you put a voltmeter on the lugs where the power lands in the unit when it stops to make sure it was still receiving power? It probably is feed by Aluminum conductors, and these can be a problem unless the terminations were made correctly 10 years ago.

If you leave it sit, will it restart by it self?

Tim
--
The difference between genius and stupidity is that genius has its limits.



whizkid3
Premium,MVM
join:2002-02-21
Queens, NY
kudos:9
reply to Busted bayou

Since the compressor amps go to zero when it stops - the opposite of what would be expected - it sounds like the internal thermal protection of the motor is cutting it off. My guess is that the compressor motor is old and fried.



SandShark
Long may you run
Premium,MVM
join:2000-05-23
Santa Fe, TX
kudos:3
reply to Busted bayou

said by Busted bayou :

but...2 ton ac..11 yrs old. unit will start and run .. comp. amps 7 ..fan 2.2 ..volts 236 ... 208 hd 80 back ..80 inside temp...unit sounds good
after 15 min the whole unit slows down and stops ..cc still pulled in ... run load amps never changed until stopped completely than goes to zero...it takes 5 sec. once it starts slowing down before it winds down and stpos .i watched incoming power as well it goes unchanged...any ideas? thanks
Some of this doesn't make any sense. The run load amps never change until stopped completely and it takes 5 seconds before "it" winds down? Until what stops completely? Until "what" winds down? The condenser fan motor? The compressor?

What is the RLA for the condenser fan motor? What is the RLA for the compressor? If the condenser fan motor is overheating, the internal overload will trip, then the motor will "wind down", but the amperage should drop to zero. If the compressor is tripping on the internal overload, it will not "wind down". It will just stop. However, if it does "wind down", chances are something mechanical in the compressor is broken, such as the crankshaft or the connecting rods. If that was the case, the compressor would not be pumping, therefore it would not be refrigerating, and the running amperage would be significantly lower than the rated RLA listed on the unit's nomenclature. Your post is a perfect example of too little information to make an educated determination of what the problem is and no amount of guessing is going to fix it.


mrknowitall

@anonymouse.org
reply to Busted bayou

just let someone else fix it because you are over complicating things or you need to work on your communicating skills. sorry if i offend you but is the truth.

there are logical steps you need to take when trouble shooting not be all over the place.

assuming just the condenser is cutting off not the whole system.

things to check if the compressor is not starting you check for bad capacitor, if it's getting power, winding ohms, if its under charged, internal over load trip, burnt wire.

things to check if condenser fan is not starting you, check capacitor, if it's getting power, winding ohms, shaft rusted getting stuck, burnt wire.

but if both are cutting off at the same time after 15 min then the most logical thing to check is a any short between the contactor and the compressor and fan. although it is weird that the cut off is after 15 minutes indicating that it may not be a short but some component failing cutting off power after 15 min. hmmmmmm...

anyway, if you fix it (or someone else does) please post back because i'm curious to find out what the problem was, thanx.



1 recommendation

reply to Busted bayou

i ran the fan by itself sure enuff it did it again...fan motor looked good .. sounded good.. drew correct amprage..replaced fan motor ..unit lives on
thanks for the help.
Volunteer relief efforts.



mrknowitall

@anonymouse.org
reply to Busted bayou

ah, i see what happened. your a/c was not cooling, you noticed the condenser wasn't running... you reset breaker...unit started... chalked it up for as being fixed...15 min. later or so, same thing. you scratch your head, turned out to be fan motor starting when reseting breaker but failing behind your back, taking the compressor along by over heating it.

so i think the brass "bearings" wore worn out on fan motor or something along those lines.

thanx for posting back


reply to Busted bayou

NO....noitall..
nothing tripped..nothing was hot ..nothing squealed..nothing over amp'd..only until the fan was isolated did i find it..yes, the fan dragged everything down. it didnt have signs to be bad.


reply to Busted bayou

davidg..you mentioned the fan motor earlier at the start of these post..thanks



mrknowitall

@anonymouse.org
reply to Busted bayou

most of the time i can't put my thoughts in to words. i didn't mean to imply the unit tripped the breaker. what i meant to imply is, usually, when a fan motor locks it will unlock when some one manually resets the breaker. most techs around here would check the breaker first, then go from there.

fan motor doesnt have to squeal to show it's on it's way out.

IMO, the only reason i would check for over ampin is if the breaker is getting tripped. but that's just me.

anyway, let me try this again, what happened is the fan motor locked up due to either rust or wear and tear. when that happens , fan motor locks, the compressor over heats and will eventually stop. i guarantee you it will over heat (from my experience anyway) the reason you didn't find it hot is because you got there when it cooled down.

i've seen this a couple of times...nothing new. it just that you are takin unnecessary steps and that got me confused.

how else would you explain the fan motor being bad if the winding are good, you put in a new cap, no over ampin, no shorts, and it had power?

how would you explain the compressor stopping due to the fan motor locking up?

if davidg posted about the cap and motor, why didnt you isolate the motor in the first place with out going on down the ladder to the next possible problem.

or for that matter isolate the compressor, or for that matter isolate the contactor and wires.

what i'm getting at is everyone that posted contributed to help you on your unorganized troubleshooting.

anyway thanx for posting back. so now you know



whizkid3
Premium,MVM
join:2002-02-21
Queens, NY
kudos:9

Huh?