Heat Pump Compressor / Condenser Fan FAQs #4

Q&A about the outdoor AC unit fan operation

Fan Difference Between Inside And Outside FAQs

Reader question: indoor fan motor will run but not outdoor fan motors

Two stage cooling, and gas heating unit. This ac had an economizer that does not work anymore but, anyways during winter or in the night time once it’s around 65 degrees outside the compressor and indoor fan motor will run but not both out door fan motors, could this be a possible bad thermostat that is killing the power to both condenser fans? During summer they will run fine or during the day when it’s decently warm or hot. 2018-11-20 by Paul jayson

Moderator reply:

There may be a misbehaving defrost cycle control board.

Question: fan runs inside but not outside

Fan runs, outside won't. 2018-09-01 by M.long

Reply:

If the indoor fan runs but the outdoor compressor/condenser doesn't COMPRESSOR / CONDENSER DIAGNOSTICS might help.

Reader question: outside fan will not come on and the unit begins to freeze up

I have a Coleman heat pump and have replaced the capacitor. The inside furnace will run and heat but the outside fan will not come on and the unit begins to freeze up, what could this be? 2017-12-05 by Angela

Mod reply:

I would look for a bad fan relay

Condenser Fan Is Making Noise

Compressor condenser is making a high squealing noise and the fan won't go on

I read all the above but I think I'm still confused. Last summer, I came home to hear my outdoor compressor unit making a high squeeling noise. I turned the AC off for the day and the noise never reappeared. Yesterday afternoon (temps in high 90's for several days)I lost air conditioning again. The outdoor compressor was making noise but the motor and fan were not running and it felt very hot to the touch.

I turned off the AC and left it off till this morning. When I turned it on, I then went outside to check compressor. Fan wasn't turning so I took a stick and manually turned the fan blades. It then started up and continued to run for about an hour until the fan stopped turning again.

I again turned the AC off for about an hour then turned it back on and the same result, fan would run for about an hour then stop spinning. Here's an observation: when the unit is off, I can take a stick and spin the blades freely in either direction. If you can help me I would appreciate it. Thanks - Don 6/21/12

Reply:

We have a separate article on diagnosing compressor noises. I found it by searching InspectApedia for "squealing compressor" - the article is titled "HVAC Noise Diagnosis & Cure: How to Evaluate Air Conditioner / Heat Pump Compressor, Air Handler, Ductwork Noises", and you can find it by clicking

on NOISE AIR CONDITIONER / HEAT PUMP in the links listed at the ARTICLE INDEX the bottom of this article .

Quoting from that article: Squeals, normal A/C compressor: Normal air conditioner compressor squealing: Some compressors emit a high pitched noise during normal operation or just at startup.

This noise should be brief and just at start-up, and will probably have always been present on the system if it's normal. More examples of compressor squealing diagnosis are in the Q&A in that article.

Reader question: condensing unit fan motor sounded bad, very noisy like bearings failing and it started to cut out

Replaced my condensing unit fan motor which sounded bad, very noisy like bearings failing and it started to cut out after 10-15 minutes of operation.
Also replaced the capacitors on condensing unit and up in the air handler. Cleaned the condensing unit coils extensively. The system worked normally for about 2 weeks, then it has started the cutting-out symptom again after 10-15 minutes.

When this happens the blower motor for the air handler is running normally, but not the new fan motor out in the condensing unit.

The relay looks too nice to be original, it looks new so I am assuming it has been replaced. I noticed if I let the unit sit for 1-2 hours after cutting out, it will start again and run almost every time throughout the night and cool normally. I was wondering if the new motor is overheating, and there is some type of safety that causes it to shut down to prevent damage?

The A/C is a 4 ton heat-pump, that is original contractor build grade Carrier brand unit which is now 14 years old, the tag is too sun-faded to pull an ID number. I am open to any feedback on this.

Thank you 2019-06-29 by HM

Moderator reply:

It's a certainly a reasonable speculation. Lots of motors have thermal overload safety controls built into the motor.
You might also want to check the voltage that's being delivered in the current being drawn.

Watch out: if you don't know how to do those tests safely you could be shocked or killed.

Check first for a seized motor, followed by a bad relay and or a loose or bad wire or connector.

Follow up: outdoor A/C compressor unit overheat & shut down because fan running backwards

I wanted to share this for everyone else's benefit and thank Dan Friedman for his input.

I brought a second HVAC tech out regarding the unit that would keep shutting down after 10-15 minutes and to safely check the operating voltage. He noticed immediately that the fan motor was wired in the reverse direction and corrected that along with using a gauge to adjust the pitch of the blades on the fan that were bent from running the wrong direction.

This created a situation where it was not dissipating the heat from the compressor but forcing the unit to work harder fighting against it. This is what kept engaging the thermal overload protection in the fan to shut it down.

The running amps (11) for the unit are now higher (18) and past the top end of the acceptable manufacturer operating range. This already aged system will fail and need to be replaced, I was hoping to limp it along another year in the AZ heat. That is now highly unrealistic.

The lesson learned is to THOROUGHLY review the tech/company that proposes to do the work. I was too focused on the overall savings and chose one vendor over another based on the quote. Cheaper is not always better, and I failed to do my due diligence using an HVAC "tech" over a solid company with properly trained and licensed technicians.

My system needed to be replaced regardless, but the potential damage could have been much worse given the electrical loads involved with the HVAC components. The risk is not worth it, and I am thankful for Dan and this website, providing the option to get an outside opinion for troubleshooting.

Reply:

HM

Thanks so much.

Your follow-up about diagnosing the A/C condenser fan will certainly help other readers.

An on-site expert will always be smarter than a guy sitting at a computer pecking at the keys down in Mexico.

The next time we read of a unit shutting down on thermal overload we'll be sure to add "is the cooling fan even running in the right direction?" diagnostic question.

BTW some motors can reverse direction following a power surge or lightning strike and will keep running backwards thereafter.

Reader question: Carrier 38TKB030300 condenser fan was making noise

Carrier 38TKB030300 condenser fan was making noise - eventually quit. I assume the bearings seized and unit stopped. I replaced the fan motor and the capacitor. Motor still does not start. Compressor seems to work fine - coils heat up and you can hear the compressor running, but no fan. 2019-06-23 by John Johnson

Moderator reply:

Sounds like a bad wiring connection or a bad fan relay

Question: My condenser fan makes a noise

My condenser fan makes a noise. Sounds like a air compressor. If I bump it the sound stops but returns next cycle. Everything seems tight. There is some play in the motor shaft but not a lot. Does this sound like the motor or blades? 2019-02-10 by Chad

Moderator reply:

Chad

Please check the diagnostics starting

at FAN, COMPRESSOR / CONDENSER UNIT https://inspectapedia.com/aircond/HVAC_Condenser_Fan.php

or try

at FAN NOISES HVAC https://inspectapedia.com/noise_diagnosis/HVAC_Noise_Diagnosis.php#Fan

And let me know what success you have

Reader question: Condensing unit fan squeals

Condensing unit fan squeals before it's at full speed then runs great. 2018-05-17 by Sax

Mod reply:

Check for

- a bad fan motor bearing

- a bad fan start capacitor

Hosed out the outdoor condenser unit, now it just hums but won't run

Just bought a home and hosed out condensing unit, probably spraying water on electrical components inside. Fired up A/C and ran fine for about an hour, then it shut down. After letting it dry out a day, I tried firing up and neither furnace nor air conditioner will operate.

A humming noise is coming from the fan blower. Concerned I may have shorted out some wire which led to the fan blower. Sick to my stomach I've worked so hard on this home. On 2020-06-23 by Ken -

Reply by (mod) - humming noise from fan blower motor

Ken

A humming blower motor is often a sign of a seized electric motor or possibly a bad relay or control board - that can happen if we get electrical components wet. So sorry, but we've all fouled up something a time or to or ... even more.

If, with power off, the blower motor spins easily I'd try replacing the start/run capacitors, and
before turning power back on I'd be sure every component is dry.

Watch out: if you're not familiar with proper safe electrical work you could be shocked or killed.

Also search InspectApedia.com for ELECTRIC MOTOR DIAGNOSIS for some easy tests

Outside fan is making a very loud noise and barely turning

You are all way more qualified than myself. I'm trying to repair a small mini bar fridge for my girlfriend. When it comes to circuit boards I'm lost I opened the thing up and found that one of the two green circuit boards makes a clicking noise (like an electric fence box, but only faster)...

I'm looking at all these small capacitors and little resistors and can figure out what the hell to do...

Can anybody give me some advice.... i dont wanna go to an electrician... i wanna try fix this at home and learn something...

obviously need some advice tho... and you ppl seem to know what your talking about. any advice would be greatly appreciated. thanks. Rob (Jan 6, 2013)

My fan coil starts only when thermostat on heat but fan does not start when in cool. External unit fan and compressor starts regularly.
It can not be the capacitor neither the fan since it starts when heat. What can be the problem? The fan unit is Carrier model Fa4Nc048. Thank you (Jan 13, 2013) Ruccardo

The fan on the outside compressor unit for the heat mode seems to be coming on late as steam comes from it for quite a long time before the fan comes on.
Is this normal or is there a control circuit adjustment for this.( Jan 13, 2013) Ernie

My outside fan is making a very loud noise and barely turning. What do I do? Nathan (Jan 14 2013)

my fan outside broke loose and is just hanging there with a bent blade...the unit shut off - Anon

Reply:

Watch out: I would turn power off and leave it off until the fan assembly can be replaced. Otherwise you're risking more-costly damage to the outdoor compressor/condenser unit or even an electrical fire.

Hit the Condenser Unit Fan, Control Board, or Motor to Make It Run FAQs

Condenser Fan Motor on Lennox Unit Won't Start Unless I Hit It

Occasionally, my condenser fan (Lennox 13ACD series) will not fire up unless I tap/hit it the side of the unit, at which point it engages immediately.

It has happened three times in the last two weeks.

Is this worth a service call, or am I looking at purchasing a new unit? - On 2020-07-13 by Brad

Reply by (mod) - condenser fan (Lennox 13ACD series) will not fire up unless I tap/hit it the side of the unit,

Brad

Thank you for a helpful diagnostic question and kudos for already taking a great Diagnostics step.

In my experience when you can get a piece of equipment to run by tapping on it there is either a loose connection or a bad relay or control switch.

That's what I would look for first.

Compressor fan won't run unless I whack the fan blades with a stick

\My house A/C turns on OK. The outside fan will not rotate unless I stick a paint mixer stick between the vent holes and give the fan blades a shove. Then it cools fine. Is the fan worn out and has it become unable to start itself? (June 12, 2012) Donn 

Reply:

Donn: you describe a classic case of a bad start/run capacitor.

See CAPACITORS for HARD STARTING MOTORS

Helpful compressor / condenser fan diagnostics - start capacitor replaced, have to tap on the control board

I have an erratic running fan on my outdoor unit, fan not running, so replace ( Dual Cap) now fan ran like new or not at all, but the compressor motor still comes on. I checked the Dual start cap, and it check out ok once, but would fail the same test later. So I replace the capacitor (exact - OEM) and the compressor motor still came on, but not the fan.

However, (the strange part) while thinking what was next, I lightly tapped on the top of the circuit board, in the area of the Fan relay ,and there others side by side, ( not for any reason ) just pondering.

Then the fan started up and ran like new. However, when the unit shut down, and restarts the fan may run great or not. When it does not, I go outside and lightly tap the top of the circuit board in location of the fan relay, the fan starts full speed, and I have cool air.

This would make a little sense if it were a (mechanical relay), but its solid-state- no contacts there?

Go figure, maybe I need to troubleshoot the entire concert board, however everything is plug and play now days, and it is very unlikely I could get a component if I where to find it. I know a bit verbose, but I feel it could be so many things, so any suggestions would be appreciated.
Thanks,
Brian

Reply:

Brian you've done some excellent diagnostics. Your description suggests that either there is a loose wire or an actual loose component on the circuit board in the compressor/condenser unit. Not only is having to tap on it not a reasonable way to live with air conditioning, it could be dangerous, risking a shock.

If you can't see and fix a loose wire or connection to the board or to other wires nearby, I'd consider replacing the circuit board. In the article above where we list types of compressor/condenser fan problems we include this topic.

 

I took a stick and pushed the fan blades and they started moving

I have a 220V condenser fan motor that is running 1/2 speed backwards when the AC is off. When AC turns on the motor changes direction (runs forward) but still only at 1/2 speed. I have replaced the contactor and dual start capacitor and that did not have any impact on the symptoms. (Sept 17, 2014) Anonymous said:

I hope someone can help me fix my goodman 3 ton heat and air unit heat pump.

The trouble I'm having is I heard this clicking noise like the fan trying to come on, but never did until I took a stick and pushed the blades and they started moving than I went inside the house and the air coming out was not cool could anyone tell me where to start checking, I,m going to try to fix this myself . (Oct 6, 2014) Diane Feltner said:

Reply:

Diane,

The problem could be a bad fan start relay or (probably) fan motor capacitor or quite possibly something else - I can't tell much from your note.

Frankly you'd be safer hiring a trained HVAC repairman. Someone with experience can not only hone in quickly on the trouble but they're more likely to have test tools, gauges, refrigerant, and parts needed.

Question: My fan won't turn on until I push it with a stick

My fan won't turn on, but when I push it with a stick, it will. However, it will stop again a few minutes later. No noticeably colder air is coming through the vents at that time it is running. Do you think it is more than just the capacitor at fault? Thank you. 2019-06-06 by Sam

Reply:

Possibly but the start / run capacitor is the place to start