air conditioning problem

[MikeyIs4Dcats]

Our AC condenser is making a squealing noise, and the fan isn't turning. Anyone have a diagnosis?

 

[amdhunter]

A mouse is stuck in the fan.

 

[Rastus]

Most likely low on coolant.

Could be a bad temperature switch that is on one of the tubes coming out of the compressor. I always cut the wires to the switch and short them out on the circuit side to make sure. If the fan comes on then, that's what it is. The temperature switch is what controls the fan coming on and going off. It keeps the pressure down by cooling the condenser.

 

[Newbian]

Originally posted by: amdhunter
A mouse is stuck in the fan.

This.

 

[Rubycon]

Originally posted by: Rastus
Most likely low on coolant.

Could be a bad temperature switch that is on one of the tubes coming out of the compressor. I always cut the wires to the switch and short them out on the circuit side to make sure. If the fan comes on then, that's what it is. The temperature switch is what controls the fan coming on and going off. It keeps the pressure down by cooling the condenser.

If the OP is discussing a commercial unit designed to run to cool a computer room say where AC is need year 'round this could be possible. Condenser fans are not needed to spin at full speed with low outside air temps. A controller often called a "motor master" can vary the speed of the motor using an input from either a head pressure sensor, sensor bulb on the liquid line, or both.

If the condenser fan motor is not turning and you're hearing a different sound than usual your motor bearings, capacitor or both may be the culprit. If you're handy with a multimeter make sure you're reading voltage on the fan relay terminals. Also verify the relay closes when there is a call for cooling. You can cheat if by jumping the R terminal to the Y terminal on the block which is the same as the thermostat calling for cooling.

The compressor contactor and condenser fan motor relay should energize (pull in) when this is commenced.

If you don't have access to a gauge manifold to connect to the service valves to verify high head pressure feel the liquid line. This is the SMALL copper line on the unit that runs to the indoor fan coil. It should be lukewarm. If it's hot as hell than the unit is running a very high head pressure and should not be run until repairs are made! There will be a high head pressure switch which will eventually open however the compressor can exceed full load amps while this pressure builds to cut out and suction pressures will also rise and you'll have significant increases in energy usage as well as insufficient cooling running like this. If you need AC and cannot wait until a repair person arrives set a water sprinkler up so it gently sprays on the outdoor unit covering as much as the exposed area of the condenser as possible. You should be able to limp by this way until repairs are made.

 

[Auggie]

That is too weird, OP - I have the EXACT same problem that just started this afternoon.

I was taking a nap with the AC on, woke up when a "whooshing" and boiling-liquid sound started coming from the ducts. I walk outside and notice the turbine fan on my AC unit is just sitting still and the entire unit is very, very hot. I shut the AC off and after 10-15 seconds the whooshing, gurgling noise stopped.

When I flipped it back on after a few minutes, I noticed the fan does start up, but after a minute, it slowly stops and the whooshing begins 20-25seconds after that. So the fan just isn't staying on to cool the radiator and freon and causing it to boil up, I guess.

Any other inputs?

 

[Auggie]

Originally posted by: Rubycon...feel the liquid line. This is the SMALL copper line on the unit that runs to the indoor fan coil. It should be lukewarm. If it's hot as hell than the unit is running a very high head pressure and should not be run until repairs are made! There will be a high head pressure switch which will eventually open however the compressor can exceed full load amps while this pressure builds to cut out and suction pressures will also rise and you'll have significant increases in energy usage as well as insufficient cooling running like this. If you need AC and cannot wait until a repair person arrives set a water sprinkler up so it gently sprays on the outdoor unit covering as much as the exposed area of the condenser as possible. You should be able to limp by this way until repairs are made.

This is my situation - I was feeling the lines (there's like two lines - one big pipe and another little copper tube with very little insulation on it) - the little copper tube was unbearably hot.

 

[Rubycon]

Originally posted by: Auggie

This is my situation - I was feeling the lines (there's like two lines - one big pipe and another little copper tube with very little insulation on it) - the little copper tube was unbearably hot.

Yes hot liquid line all the way back to XV is a sure indication of high head pressure especially if the fan is slow or not turning. Bearings (replace motor) or capacitor usually are the culprit. If the motor has open bearings you can shoot some oil in by removing the plastic plugs. This will get you through a season - MAYBE but plan on replacing the motor.

 

[Sea Moose]

Originally posted by: MikeyIs4Dcats
Our AC condenser is making a squealing noise, and the fan isn't turning. Anyone have a diagnosis?

Got pics?

fan motor is seized?
fan belts are slipping?

if you turn the power off to the unit, get a screw driver and turn the fan, does it spin freely? If it doesnt then it is siezed.
If bearings are fked oil isnt going to help.

i dont think its a capacitor, or fan wouldnt turn at all. It would just hum and throw a breaker.

 

[Rubycon]

Originally posted by: Sea Moose


i dont think its a capacitor, or fan wouldnt turn at all. It would just hum and throw a breaker.

Shaded pole motors even with locked rotors draw a fraction of compressor FLA so the breaker will stay closed. This is why the stator MUST have a thermal overload device so the windings don't catch fire in the event of a locked shaft.

 

[Sea Moose]

Originally posted by: Rubycon

Originally posted by: Sea Moose


i dont think its a capacitor, or fan wouldnt turn at all. It would just hum and throw a breaker.

Shaded pole motors even with locked rotors draw a fraction of compressor FLA so the breaker will stay closed. This is why the stator MUST have a thermal overload device so the windings don't catch fire in the event of a locked shaft.

i am just speaking from experience :thumbsup:

 

[Mill]

Originally posted by: Sea Moose

Originally posted by: MikeyIs4Dcats
Our AC condenser is making a squealing noise, and the fan isn't turning. Anyone have a diagnosis?

Got pics?

fan motor is seized?
fan belts are slipping?

if you turn the power off to the unit, get a screw driver and turn the fan, does it spin freely? If it doesnt then it is siezed.
If bearings are fked oil isnt going to help.

i dont think its a capacitor, or fan wouldnt turn at all. It would just hum and throw a breaker.

I've had a cap blow twice. Once the fan didn't move at all and the other time it did. I think a blown cap is possible for sure.

 

[Sea Moose]

Originally posted by: Mill

Originally posted by: Sea Moose

Originally posted by: MikeyIs4Dcats
Our AC condenser is making a squealing noise, and the fan isn't turning. Anyone have a diagnosis?

Got pics?

fan motor is seized?
fan belts are slipping?

if you turn the power off to the unit, get a screw driver and turn the fan, does it spin freely? If it doesnt then it is siezed.
If bearings are fked oil isnt going to help.

i dont think its a capacitor, or fan wouldnt turn at all. It would just hum and throw a breaker.

I've had a cap blow twice. Once the fan didn't move at all and the other time it did. I think a blown cap is possible for sure.

let us know, i am ok to be proved wrong :thumbsup:

 

[Rubycon]

Originally posted by: Sea Moose

let us know, i am ok to be proved wrong :thumbsup:

What are you talking about?

Unless you are actually at the site you cannot tell for sure what the exact issue is!

I'm pretty sure you would not hear the humming of a stuck condenser fan motor over the compressor. When the head pressure increases due to a non functioning condenser fan it also gets louder. Eventually it will reach full load amps and it may exceed this before the head pressure switch opens the line to the unit's contactor. Now if the head pressure switch is not working properly or has been jumped out/tampered with, then the compressor will continue to draw more amps until overcurrent protection engages. If the combined draw of the condenser fan that's stuck and compressor drawing over FLA exceeds the unit's circuit breaker or disconnect fuse capacity then it will open shutting power off.

The fan alone locked up with a FLA compressor is typically NOT enough to open the line overcurrent protection UNLESS it's underfused or the terminals are loose causing the circuit breakers to open prematurely. (thermal trip)

 

[NascarFool]

Your problem is the condenser fan motor or the capacitor. The squealing you hear would be from the very high freon pressure due to the fan not working. Most condensing units use a dual run capacitor. It's an easy fix but can get expensive depending on the size of the capacitor. I replaced one on a unit Monday and it cost the customer $235.

 

[Sea Moose]

i dont care anymore i am too sore and tired